EFFECT OF LEVELS OF IRRIGATION ON FORAGE STANDING
CROP AND QUALITY OF WW-B.DAHL (Bothriochloa bladhii )
PASTURE UNDER SUMMER GRAZING
by
CARLOS ORTEGA-OCHOA, B.S., M.S.
A DISSERTATION
IN
RANGE SCIENCE
Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of
DOCTOR OF PHILOSOPHY
Approved
Carlos Villalobos Chairperson of the Committee
Carlton M. Britton
David B. Wester
Don E. Ethridge
David B. Willis
Accepted
John Borrelli Dean of the Graduate School
May, 2006
Copyright 2006, Carlos Ortega-Ochoa ACKNOWLEDGEMENTS
I express my gratitude to my committee members Drs. Carlos Villalobos,
Carlton M. Britton, David B. Wester, Don E. Ethridge, and David B. Willis for
their intellectual advice and research experience which were always available to
me.
I recognize the financial support provided during my doctorate program
from PROMEP (SEP-México), Universidad Autónoma de Chihuahua, Arthur J.
Waterman Foundation, The Sandy Land Water Conservation District,
Summer/Dissertation Award, White Fellowship, and Department of Range,
Wildlife, and Fisheries Management. Special thanks to Mr. Charlie Craig who
gave me the opportunity to conduct my research on his farm and helped me and
my family every time we needed. Thanks also to Mr. Nick Debnam for providing
all the cattle used in my research. My appreciation goes also to Rafael Aldrich,
Miguel Avila, Rodolfo Barretero, Florentino Campoya, Luis Caro, Francisco
González, Juan González, Miguel Luna, Federico Ortega, Javier Ortega, Carlos
Ortega-Sandoval, Jessica L. Rose, Carlos Villalobos, Francisco Villanueva, and
Ricardo Soto for their help during my field work. I extend my gratitude to Dr
Sharon Myers for her invaluable contribution in the writing process of this
dissertation and Mrs. Rebecca Britton for her editing and suggestion on the early
drafts.
I extend my gratitude to the Ortega-Ochoa and Sandoval-Prieto families
for their support during this time. I really appreciated the friendship from Piña,
ii Sanchez, Villalobos, Campoya, Luna, and Villanueva families during our stage in
Lubbock, Texas.
This dissertation is dedicated to my wife Isabel, my son Carlos and my daughter Karla for their love, patience, and endless support to achieve my professional objectives. This dissertation also is a tribute to my parents Federico
(deceased) and Natividad for their love and encouragement.
iii TABLE OF CONTENTS
ACKNOWLEDGMENTS ...... ii ABSTRACT ...... vii LIST OF TABLES...... ix LIST OF FIGURES ...... xiii
CHAPTER
I. INTRODUCTION...... 1
II. LITERATURE REVIEW...... 3 Current situation of water for irrigation...... 3 Valuation and asssessment in quality of forage...... 9 Effect of water stress, heat stress, soil fertility, and plant physiology on forage qualtiy ...... 11 Old world bluestems (Bothriochloa spp) in the Southern High Plains...... 18 Old world bluestem WW-B.Dahl [Bothriochloa bladhii (Retz) S.T. Blake] in Texas...... 23 Forage quality in WW-B.Dahl grass...... 27 Cattle performance...... 28 Cattle performance in response to supplementation ...... 33 Methods of estimating forage utilization ...... 43 Economic analysis of forage/beef production systems...... 52
III. EFFECT OF LEVELS OF IRRIGATION ON FORAGE STANDING CROP AND QUALITY IN WW-B.DAHL (Bothriochloa bladhii) PASTURE UNDER SUMMER GRAZING ...... 62 Abstract ...... 62 Introduction...... 63 Materials and methods ...... 64 Results and discussion ...... 67
iv Conclusions...... 77 References ...... 91
IV. EFFECT OF LEVELS OF IRRIGATION ON PERFORMANCE OF STEERS GRAZING A WW-B.DAHL (Bothriochloa bladhii) PASTURE DURING SUMMER...... 94 Abstract ...... 94 Introduction...... 95 Materials and methods ...... 97 Results and discussion ...... 100 Conclusions...... 105 References ...... 120
V. EFFECT OF LEVELS OF IRRIGATION AND WHOLE COTTONSEED SUPPLEMENT ON FORAGE UTILIZATION BY STEERS GRAZING A WW-B.DAHL (Bothriochloa bladhii) PASTURE DURING SUMMER ...... 123 Abstract ...... 123 Introduction...... 124 Materials and methods ...... 125 Results and discussion ...... 128 Conclusions...... 132 References ...... 138
VI. ECONOMIC ANALYSIS OF BEEF PRODUCTION IN WW-B.DAHL (Bothriochloa bladhii) PASTURE UNDER DIFFERENT COMBINATIONS OF IRRIGATION AND SUPPLEMENT...... 140 Abstract ...... 140 Introduction...... 141 Materials and methods ...... 142 Results and discussion ...... 146 Conclusions...... 149 References ...... 159
v VII. OVERALL DISCUSSION AND IMPLICATIONS...... 161 Overall discussion...... 161 Implications...... 163
REFERENCES ...... 164
APPENDIX ...... 178
vi ABSTRACT
Incorporation of Old World bluestem grasses into the forage/beef production system on the Texas High Plains promises acceptable results, but information on grass responses to different moisture conditions and grazing is lacking. This study investigated the effect of three levels of irrigation on forage standing crop, forage quality, and steer performance on WW-B.Dahl
[Bothriochloa bladhii (Retz) S.T. Blake]. Forage utilization and economic analysis on the beef production capabilities of this grass were also evaluated. The study was conducted in Lubbock County, Texas during consecutive summers,
2003 and 2004, in a 54 hectare of WW-B.Dahl pasture. Three irrigation levels were established: no irrigation (NI), low irrigation (LI) applying 25.4 mm of water every 20 days, and high irrigation (HI) applying 25.4 mm of water every 10 days. Three grazing periods of 28 days also were arranged. Steers with initial average weight of 198 kg were used for the grazing trial. Steers were fed with a whole cottonseed supplement (S), (0.454 kg/head/day fed three times a week) and no supplement (NS). Forage standing crop in both years was affected by irrigation. Higher forage standing was observed for LI during the first year with
1,650 kg ha-1. For the second year HI produced the higher amount of forage with
2,211 kg ha-1. Irrigation affected crude protein (CP) content during 2004 and the highest CP value (7.3%) was detected in LI. In vitro dry matter digestibility, neutral digestible fiber, average daily gain, and average gain per hectare were not affected by irrigation in either year. Supplementation had an effect in ADG in
vii 2004. Forage utilization was not affected in 2003 and 2004 neither by irrigation
nor by supplementation. The economic analysis showed that beef production was
more profitable in dryland-no supplement scenario in 2003 and dryland-
supplement scenario in 2004. Profit in dollar/ha in 2003 and 2004 under these
scenarios was $306 and $223 respectively. Overall results for this study suggest that WW-B.Dahl has potential to improve beef production under dryland
conditions in the Texas High Plains.
viii LIST OF TABLES
2.1 Generalized sequential response of plant physiological processes and morphology to progressive increses in levels of water deficit ranging from mild to severe ...... 13
2.2 Forage yield of WW-B.Dahl at different locations and production conditions during the growing season...... 26
3.1 Water availability (mm) by level of irrigation and period in study conducted in WW-B.Dahl (Bothriochloa bladhii) pasture grazed in summer 2003 in Lubbock, County, TX...... 81
3.2 Water availability (mm) by level of irrigation and period in study conducted in WW-B.Dahl (Bothriochloa bladhii) pasture grazed in summer 2004 in Lubbock, County, TX...... 82
3.3 Effect of levels of irrigation on forage standing crop in WW-B Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003...... 83
3.4 Effect of levels of irrigation on forage standing crop in WW-B Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004...... 84
3.5 Effect of levels of irrigation on forage crude protein content in WW- B Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003...... 85
3.6 Effect of levels of irrigation on forage crude protein content in WW- B Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004...... 86
3.7 Effect of levels of irrigation on forage in vitro dry matter digestibility (IVDMD) in WW-B Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003...... 87
ix 3.8 Effect of levels of irrigation on forage in vitro dry matter digestibility (IVDMD) in WW-B Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004...... 88
3.9 Effect of levels of irrigation on forage matter neutral detergent fiber (NDF) in WW-B Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003...... 89
3.10 Effect of levels of irrigation on forage matter neutral detergent fiber (NDF) in WW-B Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004...... 90
5.1 Effect of levels of irrigation and supplement (S) and no supplement (NS) on forage utilization (%) by steers grazing in WW-B Dahl (Bothriochloa bladhii) pasture in summer 2003...... 134
5.2 Effect of levels of irrigation and supplement (S) and no supplement (NS) on forage utilization (%) by steers grazing in WW-B Dahl (Bothriochloa bladhii) pasture in summer 2004...... 135
5.3 Measurement in forage utilization and estimation of forage regrowth and forage intake of steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation high irrigation (HI), low irrigation (LI), and no irrigation (NI) in summer 2003 and 2004...... 136
5.4 Measurements in forage utilization and estimation in forage regrowth and forage intake of steers grazing in a WW-B.Dahl (Bothriochloa bladhii) pasture subject to three levels of irrigation during three grazing periods in summer 2003 and 2004...... 137
6.1 Percentage of beef production costs in 2003 in six combinations of irrigation-supplement scenarios in a WW-B.Dahl (Bothriochloa bladhii) pasture. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement ...... 155
x 6.2 Percentage of beef production cost in 2004 in six combinations of irrigation-supplement scenarios in a WW-B.Dahl (Bothriochloa bladhii) pasture. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement ...... 156
6.3 Profit per hectare ($/ha) in selected buying and selling prices in six combinations of irrigation-supplement scenarios in operational conditions in 2003. Buying price is based on 204 kg steer liveweight. Selling price is based on 250 kg steer liveweight. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI- S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement ...... 157
6.4 Profit per hectare ($/ha) in selected steer buying and selling prices in six combinations of irrigation-supplement scenarios in operation conditions in 2004. Buying price is based on 204 kg steer liveweight. Selling price is based on 295 steer liveweight. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement...... 158
A.1 Analysis of variance for forage standing crop in 2003 ...... 179
A.2 Analysis of variance for forage standing crop in 2004 ...... 179
A.3 Analysis of variance for forage crude protein content in 2003...... 180
A.4 Analysis of variance for forage crude protein content in 2004...... 180
A.5 Analysis of variance for forage in vitro dry matter digestibility in 2003...... 181
xi A.6 Analysis of variance for forage in vitro dry matter digestibility in 2004...... 181
A.7 Analysis of variance for forage neutral digestible fiber in 2003...... 182
A.8 Analysis of variance for forage neutral digestible fiber in 2004...... 182
A.9 Analysis of variance for steer performance (average daily gain per head) in 2003...... 183
A.10 Analysis of variance for steer performance (average daily gain per head) in 2004...... 184
A.11 Analysis of variance for steer performance (daily gain per ha) in 2003...... 185
A.12 Analysis of variance for steer performance (daily gain per ha) in 2004...... 186
A.13 Analysis of variance for forage utilization in 2003...... 187
A.14 Analysis of variance for forage utilization in 2004...... 188
A.15 Estimation of beef production cost ($/kg) and profit ($/ha) in six combinations of irrigation-supplement scenarios in a WW-B.Dahl pasture grazed by steers in summer 2003. LI-S low irrigation– supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement...... 189
A.16 Estimation of beef production cost ($/kg) and profit ($/ha) in six combinations of irrigation-supplement scenarios in a WW-B.Dahl pasture grazed by steers in summer 2004. LI-S low irrigation– supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement...... 190
xii LIST OF FIGURES
3.1 Precipitation monthly average in Lubbock County, Texas in 2002, 2003, 2004, and 30 years long-term average...... 79
3.2 Temperature monthly average in Lubbock County, Texas in 2003, 2004 and 30 years long-term average ...... 80
4.1 Layout of grazing trial conducted in WW-B.Dahl pasture on Craig Farm in Lubbock County, Texas in summers 2003 and 2004...... 107
4.2 Effect of level of irrigation on average daily gain (kg head-1 day-1) on steers grazing in WW-B.Dahl (Bothriochloa bladhii) pasture in summer 2003...... 108
4.3 Effect of level of supplementation (whole cottonseed at 0.0 and 0.454 kg head-1 day-1 ) on average daily gain (kg head-1 day-1) on steers grazing in WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2003...... 109
4.4 Effect of grazing period on average daily gain (kg head-1 day-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2003...... 110
4.5 Effect of level of irrigation on average daily gain (kg head-1 day-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture in summer 2004...... 111
4.6 Effect of level of supplementation (whole cottonseed at 0.0 and 0.454 kg head-1 day-1) on average daily gain (kg head-1 day-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004...... 112
4.7 Effect of grazing period on average daily gain (kg head-1 day-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004...... 113
xiii 4.8 Effect of level of irrigation on average gain per area (kg ha-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture in summer 2003...... 114
4.9 Effect of level of supplementation (whole cottonseed at 0.0 and 0.454 kg head-1 day-1) on average gain per area (kg ha-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2003...... 115
4.10 Effect of grazing period on average gain per area (kg ha-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2003...... 116
4.11 Effect of level of irrigation on average gain per area (kg ha-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004...... 117
4.12 Effect of level of supplementation (whole cottonseed at 0.0 and 0.454 kg head-1 day-1 rates) on average gain per area (kg ha-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004...... 118
4.13 Effect of grazing period on average gain per area (kg ha-1) on steers grazing on WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004...... 119
6.1 Beef production cost ($/kg) in six combinations of irrigation- supplement scenarios on WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003. LI-S low irrigation-supplement, LI- NS low irrigation-no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement...... 151
6.2 Profit per hectare ($/ha) in six combinations of irrigation-supplement scenarios on WW-B.Dahl (Bothriochloa bladhii) pasture grazed by steers in summer 2003. LI-S low irrigation-supplement, LI-NS low irrigation-no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement...... 152
xiv 6.3 Beef production cost ($/kg) in six combinations of irrigation- supplement scenarios on WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004. LI-S low irrigation-supplement, LI- NS low irrigation-no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement...... 153
6.4 Profit per hectare ($/ha) in six combinations of irrigation-supplement scenarios on WW-B.Dahl (Bothriochloa bladhii) pasture grazed by steers in summer 2004. LI-S low irrigation-supplement, LI-NS low irrigation-no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement...... 154
xv CHAPTER I
INTRODUCTION
Human activities have seriously modified the water cycle over the last three decades, with serious effects on fresh water quality and availability. Additionally, food production must be increase by 60% before 2030 to feed a growing population estimated at 8.1 billion. As a result, irrigated land is expected to reach 330 million hectares by
2025. Assessment of the current underground water situation around the world is difficult and this situation becomes more problematic in semi-arid regions where hydrological networks are not developed. Texas, in particular, depends heavily on underground water and the Texas High Plains depend solely on the Ogallala aquifer for irrigation. Currently, the Ogallala aquifer recharge is below water withdrawal. As a result, introduction to the region of Old World bluestem (Bothriochloa spp.) may be one way to reduce dependence on underground water while providing for an increase in agricultural production.
Investigation of the forage potential of WW-B.Dahl [Bothriochloa bladhii (Retz)
S.T. Blake] was conducted to explore a forage base for beef production in the Texas High
Plains. The main objective of the research was to evaluate forage yield and forage quality of WW-B.Dahl grass under different irrigation conditions as it was being grazed on during the growing season. The investigation also evaluated steer performance and analyzed the profitability of the beef production scenarios resulting from the irrigation- supplementation combinations.
1 Results from the investigation may contribute to implementation of new
alternatives in the agricultural sector of the Texas High Plains, and to alleviating dependence on underground water.
2 CHAPTER II
LITERATURE REVIEW
Current Situation of Water for Irrigation
Around the world human activities have greatly modified the water cycle over the
last three decades, affecting fresh water quality and availability. Fresh water shortages
are becoming a limiting factor in economic activities and, consequently, a social and
political issue (Shiklomanov, 1998). It is known that anthropogenic activities have
increased CO2 and NO3 emissions, strengthening the greenhouse effect. For example,
Rijsberman and Molden (2001) found that in some areas the annual renewable water
resource distribution has been adversely affected by air temperature rises of 1 or 2 ºC,
resulting in a 10% reduction of precipitation. Availability of surface water and
underground water has been limited in some regions because of erratic rainfall patterns
and recurrent and extended drought cycles.
In addition to modification in the water cycle, mismanagement of fresh water
resources has resulted in disease outbreaks, ecological disasters, and international
conflicts (Gleick, 1998). Today, problems related to underground water consumption
include overdraft, water logging and salinization, and pollution (Shah et al., 2000). It is
predicted that in 2025 more than 50% of the world population will experience water
supply shortages (Shiklomanov, 1998). This problem already exists in some regions and large cities depending on underground water for both agriculture and municipal supplies.
Additionally, population growth is escalating demand for food and fiber with increasing
3 pressure on supplies of water and other natural resources (Howell, 2001). This
population growth has forced increases in the amount of irrigated land in the last 100
years to meet food demands (Gleick, 1998). Water availability is becoming the strongest
limits on crop yields in several countries (Gregory et al., 2000).
The absence of accurate data on underground water frequently makes it difficult
to asses its availability, particularly in plains, arid and semi-arid regions, where there are
no well developed hydrological networks (Rijsberman and Molden, 2001). To alleviate
this problem, old and new water harvesting techniques have been implemented in
countries such as China, India, Jordan, Afghanistan, Chile, and the United States with the
aim of preserving and increasing underground water availability. These techniques are
aimed at increasing the rate of recharge of aquifers, storing water for domestic needs, and
increasing the amount of water available for irrigation (Shah et al., 2000). Alternative
agricultural methods of reducing water consumption for food production include improvement of irrigation technology and production of crops that consume water more efficiently (Howell, 2001).
In the United States, underground water is diminishing in certain areas because of
sustained underground water pumping, a process which reduces the ability of aquifers to
recharge. Even though data are not sufficient or reliable enough to precisely assess the current underground water conditions of all aquifers, problems such as reduction of water in lakes and streams, losses in water quality, and rising costs of pumping water are apparent (USGS, 2003). Lowering water table and shrinking stream flows have been documented in the Atlantic Coastal Plains, the High Plains, the Chicago-Milwaukee area,
4 the Pacific Northwest, and the Southwest Desert region (Hutson et al., 2004). Salt water
intrusion and land subsidence have been reported in West-Central Florida and the Gulf
Coastal Plain (Hutson et al., 2004).
Irrigation and thermoelectric power are the largest consumers of fresh water in the
United States. Water withdrawal for agriculture purposes in the United State is estimated to be from 8,000 to 10,000 m3 per hectare per year (Shiklomanov, 1998). In 2000,
irrigation accounted for approximately 188.7 km3 of water withdrawals, representing
65% of total fresh water use. Underground water withdrawals increased 14% while
surface fresh water withdrawals decreased 2% from 1985 to 2000 (Hutson et al., 2004).
Howell (2001) reported that irrigated land in the United States has increased by 2.28
million hectares since 1992. The amount of irrigated land has been increasing in regions
where water and irrigation technology are available. It is noticeable that the use of
modern efficient systems such as center pivot irrigation and micro-irrigation are
increasing. They were used on more than 50% of the all irrigated land in the United
States in 2000 (Hutson et al., 2004). Meanwhile, reductions in the amount of irrigated
land and more efficient water use have been seen in regions where drops in the water
table have increased pumping costs (Hutson et al., 2004). In the Mississippi Delta, the
Texas High Plains, South-central Colorado, the Central Valley of California, and the
Northwest, the amount of irrigated land has expanded. Additionally, reductions in the
amount of irrigated land have been documented in southern Florida, southwestern
Georgia, the rice belt in Texas and Louisiana, the Lower Rio Grande Valley, Hawaii, the
5 Northeastern Texas Panhandle, the Oklahoma Panhandle, Southwest Kansas, and parts of
Colorado (Howell, 2001).
Texas, depends heavily on underground water. Seventy-six percent of the surface land in Texas is over underground aquifers. Nine aquifers provide 95% of the total underground water. However, only 10% of underground water is available using current water withdrawal technology (TEP, 2005). Underground water availability in Texas during a drought year is estimated to be between 3,700 and 4,934 billion m3 and is expected to increase to around 18% between 2000 and 2050 (TEP, 2005). In 1990, 50% of the total water used for all purposes was withdrawn from aquifers. On the other hand, agricultural irrigation accounted for 71% and 29% went to other water uses. An estimated reduction of 17% is anticipated in a 50 year planning horizon (TWRI, 2002).
Reduction in water use was reported to be 19,365 million m3 from 1980 to 1990 in Texas due to decrease of land used for agriculture. In 2000, water used in the state was 20,266 million m3; underground water supplied 12,335 million m3.
The State of Texas, however, does not regulate withdrawal and use of underground water. Both underground and surface water are governed by the rule of capture: both sources of water can be sold, leased, or bartered by the land surface owner.
Underground water districts at local levels are empowered to set rules and regulations to conserve, preserve, protect, and promote recharge of the underground water aquifers within their limits (TWDB, 2004a). There are 87 underground water conservation districts in Texas, covering partially or entirely 138 counties (TWDB, 2004b).
6 In Texas, population is shifting from rural to urban areas, increasing competition
for water between agricultural interests and municipalities. Analysts predict that
municipal water use will surpass agricultural use by 2040 (TWDB, 2004a). As a result,
the Texas Water Development Board (TWDB) has proposed a set of recommendations to
the state legislature: 1) protect rural communities’ access to water resources, ensuring the
economic development of rural areas of Texas; 2) provide financial incentives to the
agricultural sector to enhance water conservation, diverting those water savings toward
other economic activities and; 3) evaluate the impact of sales of water rights and
groundwater for other uses in rural areas. The TWDB also suggests the following
agricultural practices to conserve water: irrigation scheduling, improved irrigation system
efficiency, enhanced conveyance efficiency, practicing conservation tillage, and
providing economic incentives for irrigation suspension, and development of water use efficient crops (TWRI, 2000).
In the Texas High Plains, the Ogallala aquifer is almost the only source of
underground water. It is the largest water bearing unit, covering 46 counties in all or in
part and holding 90% of the total underground water in Texas (Baker, 2005; TEP, 2005).
Water withdrawals from the Ogallala aquifer are used predominantly for irrigation
(Howell, 2001). Irrigated agriculture began in the early 1900s, increasing gradually until the middle of the 1940s. Today, irrigated land in the Texas High Plains represents 65% of the total irrigated land in the United States (HPWD, 2004). Moreover, the amount of land irrigated with underground water increased quickly from 1940s until 1959.
Thereafter, the rate of increase slowed until 1980. By then there were 3.52 million
7 hectares under irrigation, approximately the same amount registered in 1959, but by 1989 only 1.24 million hectares were irrigated (Baker, 2005; TWDB, 2004a). Irrigated land in
the Texas High Plains is, however, expected to decline to somewhat more than 50% of
the current amount (Baker, 2005). Currently, reductions in irrigated land have been
reported in the northeastern Texas Panhandle. On the other hand, increases in the amount
of irrigated land have been reported in relation to Dawson and Gaines counties’ cotton
and peanut crops and Dallam County’s corn crops, as a result of improvements in
irrigation practices in other counties in the Texas High Plains (Howell, 2001). These
reports illustrate great achievement in underground water savings in the region. First,
improvements in water use efficiency came about through irrigation technology and
second, the amount of agricultural land enrolled in the Conservation Reserve Program
increased. As a result it is estimated that from 50 to 75% water use efficiency was
achieved in the 1970s and 1990 s. A drought period from 1992 to 1996 in the Texas
High Plains also forced agricultural producers to increase water withdrawals from the
aquifer to supplement precipitation, lowering the water table 0.41 meter per year on average from 1992 to 1997 (HPWD, 2004).
Currently, recharge in the Ogallala aquifer is far behind water withdrawal because
of the considerable demand for water to irrigate crops. Water levels in the High Plains
aquifer have fallen. The saturated thickness of the Ogallala aquifer in Castro, Crosby,
Floyd, Hale, Lubbock, Parmer, and Swisher counties has decreased more than 50% since the expansion of irrigated agriculture in the region. In these counties, the amount of irrigated land has been reduced from 2.2 to 1.7 million hectares as a result of the
8 increased cost of water pumping lift and well yield reduction (Baker, 2005). Infiltration
of precipitation is the main source of aquifer recharge. Only an estimated 25.4 mm of
precipitation annually is estimated to reach the water table due to the small amount of
precipitation, high evaporation rates, and low rates of infiltration (TWDB, 2004a). In the
Texas High Plains region, recharge is estimated at 0.63 mm per year, representing about
0.1% of the total precipitation in the area. Another source of recharge is irrigation water
which returns to the aquifer. In Castro and Parmer Counties, it is estimated that 54% of
the water used in irrigation returns to the aquifer. Natural underground water discharge
occurs through seeps and springs along the Canadian River, but the highest discharge rate is recorded by artificial wells (Baker, 2005).
Valuation and assessment of forage quality.
The value of forage has been recognized since domestication of animals (Allen
and Segarra, 2001), and have been selected for high quality with and eye to increasing
production since the 1880s. There two food component categories are used to describe
forage quality, low quality is determined by quantity of cell wall constituents such as
polysaccharides, lignin, phenolics, silica, cutin, certain proteins, and water. High quality
is determined by content of organic acids, proteins, lipids, soluble minerals, and
nonstructural carbohydrates (Asay et al., 2002). High quality forages whose value can be
measured by satisfactory or high animal performance. Forage quality depends on
nutrients concentration, animals forage intake and the resulting products of the
fermentation and metabolism processes within animals (Buxton, 1996; Ford, 1999)
9 resulting in, for instance production of beef, milk, wool, mohair, and antlers (Ford, 1999).
Fahey and Hussein (1999) defined forage quality in the framework of animal nutrition as
a product of intake and digestibility of forage, with intake the more important of the two.
To assess forage quality, early researchers did not use laboratory techniques and
animal feeding trials as researchers do today. They investigated improvement of forage yield and quality, selecting forages based on plant vigor, disease resistance, late maturity, and perhaps, animal palatability criteria (Casler and Vogel, 1999). Today, forage quality is assessed using either laboratory techniques or animal feeding trials. Quantity of crude protein content (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), in vitro dry matter digestibility (IVDMD), and hemicellulose are the features most often evaluated to assess forage quality as an alternatives to feeding trials (Jensen et al., 2003).
Methodology such as the two-stage in vitro method to analyze digestibility developed by
Tilley and Terry is still used for reference purposes and is considered a breakthrough in
forage quality evaluation. Near infrared reflectance spectroscopy (NIRS), a more
sophisticated analytical method, has been successful in evaluating forage quality and is
fast and inexpensive. Nuclear magnetic resonance (NMR) scanning and microrospectrophotometry for cell wall analysis, ultraviolet fluorescence microscopy for
analysis of phenolics in cell walls, light microscopy, scanning electron microscopy, and transmission electron microscopy analyses alone or in combination with
immunocytochemical procedures are enlisted to better understand the interaction between
plant and microorganismos through the digestion process (Fahey and Hussein, 1999).
10 Normally, forage quality is estimated in vitro, due to the greater costs and time
entailed in feeding trials. However, forage quality can be verified by animal performance
when forage is consumed by livestock. Ball et al. (1991), cited by Allen and Segarra
(2001), suggested that animal performance is a better indicator of forage quality than is in
vitro analysis.
Effects of water stress, heat stress, soil fertility, and plant physiology on forage quality
Achieving high forage quality under everyday environmental conditions which included global warming, recurrent floods, extended drought cycles, and CO2 and NO3
increase is the focus of many rangeland, forage, and animal nutrition scientists around the
world. Seek to meet the increasing demand for high quality food (Jensen et al., 2003).
Their efforts have involved simulating plant-animal interactions by manipulating
environmental, physical, and biological variables to maximize forage yield and quality.
Different models have been created to maximize productivity of plants and animals and
minimize adverse environmental effects (Ghannoum et al., 2003). Environmental factors,
such as water stress, heat stress, and deficient soil nutrient supply, limit optimal plant
development. Forage species and plant morphology also influence forage quality
(Buxton, 1996).
Water stress
Water is an essential component of physiological functions in all organisms. In
plants, water, which is found in cells and tissues constitutes 80 to 90% of the weight of
11 herbaceous tissue. Water facilitates translocation and solubility of nutrients, osmotic
processes, gas exchanges, and cell growth (Brown, 1995).
Typically, water deficit or water stress occurs when the normal physiological
activity in plants is disturbed by reduction of the internal water potential and pressure potential of tissues. This stress has the greatest consequences when plants are growing or
are in a reproductive stage, limiting biomass production. Negative effects depend on
degree of dehydration, plant age, developmental stage, and occurrence of previous drastic
seasonal changes (Brown, 1995). The effects of continuous, recurrent, and intense water
deficit in plants are summarized in Table 2.1.
Currently, researchers are focusing on physiological and metabolic changes at the
cell level, investigating gas exchange, enzymatic pathways, and amino acid
arrangements, in order to explain the relatively high crude protein content and
digestibility of plants exposed to water stress (Ghannoum et al., 2003). Approaches to
testing forage quality under water stress conditions have not yet achieved high levels of
accuracy. At present, the crop water stress index (CWSI) is used to assess forage yield of
plants under water deficit stress conditions. Halim et al. (1990) used the CWSI in alfalfa
(medicago sativa) and found that water reduction incited stomatal closure, reduced
transpiration, and increased canopy temperature. They concluded that CWSI should not
be recommended to evaluate forage quality because the components of leaves and stems
do not respond in the same way to water stress conditions; they found that only neutral
digestible fiber (NDF) was closely related to CWSI. The ratio of current carbon dioxide
assimilation to potential assimilation (A/Ao) is another index of water use efficiency
12 (WUE). It is used to screen germplasm to identify genotypes with strong responses to drought conditions (Coyne et al. 1995).
Table 2.1 Generalized sequential responses of plant physiological processes and morphology to progressive increases in levels of water deficit ranging from mild to severe.
Intensity of water deficit Mild Mildly Severe Severe Effect
Decrease in cell growth Slowing or cessation of Death of tissues and and division photosynthesis organs
Decline in cell wall Increase of temperature in Plant death synthesis leaf surface
Decrease in protein Decrease of respiration synthesis
Cessation of Decrease in xylem protochlorophyll formation conductance
Decline in enzymatic Accumulation of proline activity and other amino acids
Increase in ABA Increase of sugar concentration
Decline or cessation of leaf Decrease of starch expansion
Closure of stomata Wilting, folding and rolling of leaves
Beginning of membrane disorganization
Adapted from Brown, 1995. The water relations of range plants: Adaptations to water deficit, page 322.
13 Many investigations suggest that grasses growing in a water deficient environment do not achieve their growth potential, tending to reduce their leaf content and accelerate their development into the reproductive stage rapidly by producing seed heads which result in dry matter digestibility reduction (Han et al., 2003). Evidence indicates that water stress inhibits tiller and branch growth in forage, resulting in accelerated death of current tillers. Water stress also accelerates senescence of old leaves, reducing leaf mass, and diminishing protein and carbohydrates content above parts of plants. If the water stress is mild, however, digestibility may be enhanced regardless of plant age. No consistent pattern in crude protein content due to water stress has been found, however, under severe drought conditions, plants normally lose their leaves and perennial plants turn dormant, resulting in quality loss (Buxton, 1996). On the other hand, when moisture is not a limiting factor, temperature promotes plant growth, favoring production of stems rather than leaves, which normally reduces the digestibility of forage (Redfearn, 1999). Linn and Martin (1999), however, contradict the previous statements. They reported that water stress reduces plant growth and increases the leaf:stem ratio, digestibility, and anti-quality factors.
Water stress tolerantion mechanisms
Studies have been conducted to identify mechanisms which can explain drought tolerant behavior in range plants (Ranieri et al., 1998). When water potential in leaves is diminished, plants experience several morphological and biochemical changes. Some of them induce the plant to adjust its protein and amino acid metabolism in order to adjust to
14 the new environment. Mechanisms to make osmotic adjustments, modify the metabolism
of many enzymes, and survive water stress exist in grasses. These mechanisms include
storage of amino acid and sugars, accumulation of free amino acids in leaves a process which promotes protein synthesis, reduces oxidation, and increases protein hydrolysis
(Ranieri et al., 1998).
Drought tolerance in plants may be delimited by alteration of protein synthesis.
Jaing and Huang (2002) suggested that drought induced proteins, such as those of the dehydrin family, tend to accumulate in water stressed plants, helping protect cells from certain kinds of damage. Dehydrin proteins are hydrophilic and heat stable. Jaing and
Huang found that application of asbscisic acid (ABA) on tall fescue grasses under drought conditions played an important role in protecting them from further dehydration
damage by delaying protein synthesis.
Forage plants growing under erratic and deficient water supply are often reported to contain higher quality nutrients than plants which have had sufficient moisture. Erratic water supply forces the plant to increase the thickness and rigidity of its cell-walls to accumulate phenolic acid esters. These amino acids have been identified by some researchers as responsible for slowing the rate of degradation in grasses (Deetz et al.,
1996).
Many studies has shown drought resistance in Bothriochloa spp. Forage
production tested under greenhouse conditions in four Bothriochloa accessions showed a
strong positive relationship between the degree of stomatal association and CO2 uptake
(Coyne et al., 1995), giving those grasses capability to tolerate water deficits during the
15 growing season. Derner et al. (2001) found that C4 grasses had better response to
atmospheric CO2 enhancement at times when a water deficit exists. Seligman and
Sinclair (1995) reported that plants grown under elevated CO2 conditions increased their
nonstructural carbohydrate content (starches and sugars) and decreased their lignin
concentration, making them more digestible and enhancing the forage value.
Brown (1995) noted that studies conducted on Caucasian bluestem resulted in
higher leaf xylem potential and higher stomatal conductance in heavily grazed plants than
in lightly grazed plants. He speculated that grazing improved water uses in leaf tissue by
increasing the ratio of absorbent surface to transpiring leaf surface area.
Heat stress
Temperature stress and drought stress are highly correlated environmental
conditions (Jiang and Huang, 2001), typically showing up simultaneously. Their effects
are hard to isolate. Daytime temperature variation affects forage quality, and fluctuation
in nonstructural carbohydrate content have been reported in forages, resulting in lower
values before sunrise and higher values in the late afternoon. Further, higher crude
protein content in forages has been measured in the late afternoon (Redfearn, 1999).
Fahey and Hussein (1999) stated that as temperature rises 1 ºC digestibility decreases by
1%.
16 Plant physiology
Environmental and agronomic factors are involved in acceleration and retardation
of the forage maturity process. Fluctuations in quality are observed between and within
years, seasons, geographic locations, and harvesting times, even when forage is harvested
at the same stage of grwoth (Buxton, 1996). Forage quality, which varies among plant parts, is influenced principally by forage maturity. Concentration of crude protein in plant part is typically lowest in stems, while leaf blades typically have twice as much crude protein as stems. Advanced forage maturity affects ruminant digestive processes, as well, and results in lower animal performance (Ward et al., 1990). As a rule, a quarter of the protein content in forage escapes ruminal fermentation. In some animal species, the longer plants mature, higher proportion of crude protein is available in the lower digestive tract (Buxton, 1996). On the other hand, forage digestibility is largely regulated by cell wall concentration. Higher cell wall concentration is present in stems rather than in leaves in the majority of forages. Thus, digestibility of stems normally decreases as the plant matures. Greater differences in digestibility of leaves and stems are more evident in forage legumes than in forage grasses. For example, plants with higher numbers of reproductive tillers show faster declines in digestibility. On average, Buxton
(1996) observed a reduction of 4 g kg-1 day-1 in plants with a moderate number of
reproductive tiller, whereas plants with abundant reproductive tillers showed reduction in digestibility of 6 g kg-1 day-1.
Improvements in forage quality are not highly correlated with increase in forage
yield. However, digestibility has a positive relationship to cattle performance; a 1%
17 increment in IVDMD represents a 2.3% increment in average daily gain. Additionally,
improvement in forage IVDMD also has been documented when genetic improvement
was applied to forage CP content (Casler and Vogel, 1999). Hatfield et al. (1999)
suggested that genetic selection in forages may be improved by focusing on increased
pectin content in cell walls to improve digestibility and protein utilization, since the pectin fraction is highly degraded by ruminal microbes.
Old world bluestems (Bothriochloa spp) in the Southern High Plains
Old World bluestem species were brought to the United States from Europe and
Asia, mainly Russia, India, Afghanistan, Pakistan, Iraq, and Turkey (McCollum, 2000).
These grasses consist of an assorted group well adapted to the Southern High Plains
environmental conditions (Dabo et al., 1988). According to Coyne and Bradford (1985),
there have been 700 to 800 accessions of Old World bluestems at the South Plains
Research Station in Woodward, Oklahoma. Since then, several studies have been done to
evaluate Old World bluestem forage production capability and forage quality (Coyne and
Bradford, 1985), but information regarding the chemical composition of Old World bluestem grasses is still lacking (Dabo et al., 1988).
Almost all grasses used in Texas and Oklahoma for range improvement, irrigated
pastures, and soil conservation purposes have been introduced from European and Asiatic
countries (White and DeWald, 1996; Sanderson et al., 1999). Old World bluestem
grasses (Bothriochloa spp.) have been used in the Southern High Plains since the early
1920s (Dabo et al., 1987) and became available for commercial use in the 1930s with the
18 release of the Caucasian Old World bluestems (Dalrymple et al., 1984). Bell and Caudle
(1994) reported that approximately 670,000 hectares had been seeded with varieties of
Old World bluestems in pure stands or in mixtures in regions such as the Rolling Plains,
South Plains, and the Panhandle of Texas. Berg and Sims (1995) noted that approximately 2 million hectares had been established in Texas and Oklahoma, 50% of them seeded in the last 10 years (White and Dewald, 1996). Hodges and Bidwell (1993) reported that this amount of land seeded with Old World bluestems has great potential for beef production system of the region.
Forage grasses with high water use efficiency have great potential for being involved into forage/livestock systems in arid and semi-arid environments (Philipp,
2004). Though Old World species (Bothriochloa spp.) have been cultivated for several years in the semi-arid Texas High Plains little information is available regarding water use efficiency of these grasses in the region. The introduction of Old World bluestems to the region may contribute in designing forage/livestock systems with lower water requirements. Thus, these alternative agricultural systems may reduce the current high rates of underground water extraction from the Ogallala aquifer (Philipp, 2004) and complement beef production in places where crops such as wheat and cotton show low rates of return (Wang, et al. 1992; Hodges and Bidwell 1996; Allen, et al., 2005).
19 Characteristics of old world bluestem (Bothriochloa spp)
Old World bluestem grasses have characteristics which have attracted the
attention of both researchers and producers. These include superior performance in
comparison to Andropogon and other introduced species (Dabo et al., 1987). The Old
World bluestems are warm-season perennial bunchgrass grasses with a C4 photosynthetic
pathway. Most of them present apomictic reproductive behavior (Coyne and Bradford,
1985). According to several studies, Old World bluestems have high forage potential,
high forage quality in summer, good growth performance in different pH ranges, good
response to management, and establish themselves aggresively. In addition, they are
drought tolerant, grazing resistant, and well accepted by cattle (Dabo, et al., 1988;
Hodges and Bidwell, 1993; McCollum, 2000). Old World bluestem grasses are adapted
to loam or clay loam soils and respond well to nitrogen fertilization. In most of the
Bothriochloa species, seasonal growth patterns normally start in late April, reaching peak
growth by mid-July and then declining. In August and September, there may be some
regrowth if moisture is available (Hodges and Bidwell, 1993). In some species such as
WW-Iron Master and Caucasian, regrowth occurs in June (Dabo et al., 1988; White and
DeWald, 1996).
Old World bluestem grasses are easier to establish than native grasses, requiring only one growing season. They have higher seedling vigor, better leaf:stem ratio, more tillers, and more leaves per tiller. These characteristics allow them to produce a greater amount of forage than do native species, as they increase tiller regrowth under heavy stocking rates and good moisture conditions (Coyne and Bradford, 1985). A study
20 carried out in College Station, Texas, found that the forage production yield of Old World bluestem grasses is four times greater than that of native range forage managed under good conditions (Wang et al., 1992).
Dabo et al. (1997) conducted a study with Caucasian (B. Caucasica), Ganada and
WW-Spar (both B. ischaemum) in greenhouse conditions. They compared anatomical and histological features of stem tissues and related these features to the rate and extent of degradation by ruminal microorganisms. They observed that mature stems had larger fungal colonization on the parenchyma and sclerenchyma cells than in leaves in growing stage. They suggested that these fungal colonies may contribute increase in sclerenchyma degradation in Ganada and WW-Spar by fracturing, splitting, and pitting the cell walls.
Svejcar and Christiansen (1987) conducted a two year study measuring the effect of grazing pressure on TNC concentration in Caucasian bluestem. They reported that
Caucasian bluestem crown structure maintains a satisfactory amount of TNC when heavily grazed. Arrangement of stems in the crown of heavily grazed plants seemingly assists retention of a pool of TNC available for regrowth. This arrangement also protects new growing points. Grazing tolerance in Caucasian bluestem seems to be supported by the plant architecture, which protects the plant crown from grazing destruction (Svejcar and Christiansen, 1987). Additionally, frequent grazing or defoliation in Caucasian bluestem may increase water use efficiency by enhancing leaf water potentials and conservation of soil water (Svejcar and Christiansen 1987; Masters and Britton 1988).
21 Management of old world bluestems (Bothriochloa spp).
Criteria for selecting Old World bluestem grasses should be based on climate, soil and management conditions. It is recommended that most Old World bluestem varieties be sown in April using 2 lbs?ac PLS (Berg et al., 1999). Bell and Caudle (1994) pointed out that Old World bluestems germinate later than native grasses, and require good moisture conditions in spring and summer for good establishment.
Soil fertility and stage of growth have an effect on forage quality of grasses, including Old World bluestems (Hodges and Bidwell, 1993). Old World bluestems respond well to nitrogen fertilization (Berg, 1988; Bell and Caudle, 1994; McCollum,
2000). Applying from 33.6 to 78.4 kilograms per hectare in the spring under dryland conditions is commonly recommended. For the Panhandle region, McCollum (2000) and
Bell and Caudle (1994) recommend applying from 44.8 to 67.2 kilograms per hectare.
Berg and Sims (1995) suggest applying 70 kg per ha for better forage yield and cattle performance. When soil is deficient in phosphorous, application of 56 to 112 kilograms per hectare may increase forage production from 10 to 70% (Bell and Caudle, 1994).
Maintaining high forage quality throughout the growing season is a challenge for the forage/livestock system (Coyne and Bradford, 1987). One recommendation is to maintain heavier stocking density early in the growing season, taking advantage of the high production and high quality of forage. Another is to rest plants when quality goes down, which normally occurs in the fall (Coyne and Bradford, 1987; Hodges and
Bidwell, 1993).
22 Old world bluestem WW-B.Dahl [Bothriochloa bladhii (Retz) S.T. Blake] in Texas
WW-B.Dahl, formerly known as WW-857, was originally collected in Manali,
India. In 1960 it was brought to the Southern Plains Research Station in Woodward,
Oklahoma. After 15 years of adaptation and production trials, WW-857 was selected and finally developed into WW-B.Dahl (Bell and Caudle, 1994; Dewald et al., 1995). WW-
B.Dahl was jointly released in 1994 by the USDA-ARS, USDA-SCS, Texas Tech
University and the Texas Agricultural Experimental Station, and is the most recently released variety of the Old World bluestem species. It was named after the late Dr. Bill
Dahl, a professor in the Department of Range, Wildlife, and Fisheries Management at
Texas Tech University. Dr. Dahl tested this grass under dryland conditions at Texas
Tech Experimental Ranch at Justiceburg, Texas (Dewald et al., 1995).
WW-B.Dahl is well adapted to the southern plains and to land conditions in
southern and central Texas (McCollum, 2000) where there are medium to fine textured
soils (Dahl et al., 1988), and where annual rainfall ranges from 381 to 889 mm (Bell and
Caudle, 1994). It is well adapted to sandy loam and clay soils. It supports a pH range
from 6.7 to 8.4 and is more tolerant of acid soil conditions than other Old World
bluestems (Dewald et al., 1995). McCollum (2000) mentioned that WW-B.Dahl
responds well to nitrogen fertilization application, which can be single or split, according
to moisture conditions in the growing season.
Several studies have been conducted in Texas to evaluate WW.B.Dahl responses to diverse soil and management conditions. Blair et al. (1991) found that WW-857
(WW-B.Dahl) had better establishment and growth response in Yahola fine sandy loam,
23 Stamford clay and Berda loam soils than in Lincoln loamy fine sand soil. After one year
of establishment the number of plants doubled in the former. They observed that forage
yield was double that of other Old World bluestems and five times higher than grasses in
adjacent native rangeland. White et al. (1996) mentioned that WW-B.Dahl produces a
great amount of forage both in dry land conditions and irrigated conditions. Research
conducted in Texas and New Mexico has shown that it produced more forage than did
other bluestems. In the High and Southern High Plains regions under dryland conditions,
production ranges from 0.5 to 3 tons annually, and under irrigation, from 6.7 to 11.2 tons
per hectare (McCollum, 2000).
Research conducted on three Old World bluestems species in New Deal, Texas by
Philipp (2004), reported that large basal area, canopy characteristic and arrangement, and
amount of leaves within the canopy may confer grazing advantages to WW-B.Dahl over
those of Caucasian and Spar. Philipp (2004) noticed that WW-B.Dahl continued growing
in the late season, amassing more biomass between September and October than did
Caucasian and Spar. The same observation was made by Hodges and Bidwell (1993).
Philipp (2004) also noted that under conditions of frequent irrigation, WW-B.Dahl
reduced its basal area and increased bare soil portion. He suggested that accumulation of
above-ground biomass might have limited the amount of light reaching lower parts of the
plant.
Philipp (2004) reported that on average, in 2001, WW-B.Dahl produced 2,400 kg per hectare under dryland treatment. The 2003 was characterized by extremely low precipitation and therefore, soil water content for plant growth was supplied by autumn
24 and winter precipitation from the previous year. All forage growth was generated in July
in all grasses. He suggested that Caucasian, Spar, and WW-B.Dahl grasses could
potentially be incorporated into agricultural systems in the Texas High Plains. This
suggestion was based on forage production yield of these grasses in dryland conditions.
He also mentioned that in all species tested under medium and low irrigation levels,
seemed to be more efficient in water use than under high level of irrigation and dryland
conditions. He reported that Caucasian (18.4 kg ha-1 mm-1) and WW-B.Dahl (19.4 kg ha-
1 mm-1) were both more efficient in water use than Spar.
Bezanilla (2002) conducted a two year study in a WW-B.Dahl pasture in Idalou,
Texas. He evaluated forage production subject to two levels of irrigation and two grazing systems in summer. Irrigated pastures received 75 and 100 mm of water during the grazing season in 1999 and 2000 respectively. The author found that in 1999, the level of irrigation had a positive effect on forage production. Irrigated pastures produced higher yield than nonirrigated pastures at the end of the grazing trial with 4,150.6 and 2,914.7 kg ha-1, respectively. Grazing system had no effect on forage production. In 2000, forage
production also was higher in irrigated pastures.
In Stephenville and Temple, Texas, Sanderson et al. (1999) evaluated three Old
World bluestems over a two-year period, finding that WW-B.Dahl performed better than relatives such as WW-Spar and WW-Iron Master. WW-B.Dahl had the largest and heaviest number of tillers per plant, resulting in better yields. WW-B.Dahl also showed later maturation than WW-Spar and WW-Iron Master. WW-B.Dahl had been selected for their study because of its high leaf:stem ratio, late maturation, and broad leaves. The
25 authors concluded that WW-B.Dahl is more productive than its relatives and well adapted to the central and southern parts of Texas. Table 2.2 shows forage production of WW-
B.Dahl at different locations and under different production systems.
Table 2.2 Forage yield of WW-B.Dahl at different locations and production conditions during the growing season Location Years of Study Conditions Yield (kg/ha)
Woodward, OK 3 Dryland 6,567
Woodward, OK 3 Dryland 4,029
Stephenville, TX 2 Dryland 8,497
Temple, TX 2 Dryland 7,820
Justiceburg, TX 1 Dryland 3,639
Los Lunas, NM 2 Irrigated 12,772
Las Cruces, NM 3 Irrigated 19,118
Idalou, TX 2 Irrigated 3,957
Idalou, TX 2 Irrigated 5,833
San Luis, Argentina 3 Dryland 8,333
Sources: Blair et al., 1992; Sanderson et al., 1999; McCollum, 2000; Bezanilla, 2002; Villalobos et al., 2002; Veneciano and Frigerio 2003.
26 Forage quality of WW-B.Dahl
Nutritive value of Old World bluestem grasses under different irrigation levels
has not seen thoroughly studied in the Texas High Plains region. Studies carried out in other regions, however, have found that crude protein content and rate of digestibility of
Old World bluestems were affected by species, management, environmental conditions, and regional topography (Philipp, 2004).
Philipp (2004) investigated forage quality of three Old World bluestem species
WW-B. Dahl (B. bladhii), Spar (B. ischaemum), and Caucasian (B. caucasica), cultivated at different moisture levels. He found that all grasses under dryland conditions, dry matter digestibility was higher at the beginning of the growing season and crude protein content increased as the growing season advanced. He also noted that total nonstructural carbohydrates (TNC) decreased as amount of irrigation increased, but at the end of the growing season, TNC tended to increase at all irrigation levels. He reported differences in crude protein content in all species throughout the period of study. On average, WW-
B.Dahl showed higher CP than did Caucasian and Spar in almost all months sampled over the three years. Grasses underwent morphological changes as the growing season advanced. As grasses mature leaf:stem ratio declined. In the majority of the monthly
samples, lower leaf:stem ratios were observed in plants being irrigated, resulting in larger
differences in CP content between dryland treatment and irrigated treatments than among
irrigated treatments.
The effect of defoliation and deferment on forage yield and forage quality of Old
World bluestems have been studied in Argentina. Veneciano and Frigerio (2003)
27 evaluated WW-B. Dahl, WW-Spar, Plains, and sideoats grama [Bouteloua curtipendula
(Mich.) Torrey] under four different defoliation schedules with deferment. Measurement in crude protein content showed no difference (P > 0.05) in crude protein yield between treatments.
Cattle performance
The biological interface of animal-forage consumption is poorly understood
(Burns and Sollenberger, 2002). Forage quality and quantity are directly involved in
forage intake and subsequent cattle performance (Popp et al., 1997), but little information
is available about nutrient requirements in relation to seasonal changes in forage quality,
animal diet selection, and voluntary intake (Paterson et al., 1996). In warm season,
characteristics of the canopy architecture of grasses, including height, leaf density, and
leaf weight are positive related with grazing behavior. Green leaf proportion and mass
also affect animal daily weight gain (Burns and Sollenberger, 2002). Forage availability
key to cattle performance. Reduction in forage availability negatively affects average
daily gain and gain per area. A study conducted by McCollum et al. (1993) cited by
Paisley (2000) found that when forage availability is below 6.8 to 9 kg of forage/45.4 kg
BW/day, quality and quantity of diet decrease dramatically. They suggest that 1,120 to
2,240 kg of forage per hectare should be available to maintain positive cattle
performance. Another study (Ellis et al., 1984, cited by Paisley, 2000) found that when
forage allowance dropped below 13.6 kg/45.4 kg of BW, forage intake and digestibility
dropped significantly (Paisley, 2000).
28
Cattle performance in irrigated pastures in the High Plains
Livestock producers are now seeking ways to increase forage production in
irrigated pastures in the High Plains, where pastures have been seen as a complement to
native rangeland and other source of forage (Nichols et al., 1993). Complementary
forage systems are intended to overcome seasonal forage shortages and nutritional
deficiencies entailed by single forage. They provide some advantages, including
improvement in range condition, efficiency in forage utilization, and increases in
stocking rate. They also may significantly increase beef production in the High Plains
(Gillen and Berg, 2001).
Complementary forage systems composed of native pasture and Old World bluestem make it possible to take advantage of spring growth of native grasses as well as
the short season and higher productive potential of Old World bluestem grass. Guillen
and Berg (2001) conducted a five year study evaluating two stocker production systems which evaluated the productivity of a native grassland system mixed with native-Old
World bluestem in four management grazing periods. In the two first management grazing periods (winter and early native), steers ADG was higher in the native system
than in the Old World bluestem-native system. ADG in a native system was 0.34 and
0.85 kg per head for winter and early winter, respectively. In the Old World bluestem-
native systems, ADG was 0.19 and 0.70 kg per head for winter and early winter,
respectively. A reverse trend was observed during the third management period (Old
World bluestem system). ADG was 1.01 kg per head in the Old World bluestem-native
29 system and 0.94 kg head-1 in the native system. In the late native management period
when all steers were in native pasture, there was no significant different in ADG between systems. ADG were 0.45 and 0.62 kg per head for the native and Old World bluestem- native systems, respectively. The Old World bluestem-native system showed a 64% increment in beef production per ha compared to the native system. The stocking rate in the Old World bluestem-native system was, however, 69% higher than in the native system.
Kloppenburg et al. (1995) studied performance of steers grazing different sources
of forage all year round, according to performance in native rangeland and in warm-
season perennial grasses. Performance in warm season Bermudagrass [(Cynodon
dactylon (L.) Pers.] was compared with performance in bluestem (Bothriochloa
ischaemum Keng.). Results in steer gains in warm season grasses and in rangeland were similar. Steers grazing rangeland (72 kg) and bermudagrass (72 kg), however, gain than those in bluestem (59 kg).
Bezanilla (2002) evaluated steer performance in WW-B.Dahl pasture subject to
two irrigation treatment, two grazing systems, and three grazing periods during summer
in Idalou, Texas. A variable stocking rate was used in 1999 (from 1.43 to 7.85 AU ha-1)
and fixed stocking rate in 2000 (1.76 AU ha-1). In 1999 he found significant difference
(P < 0.05) between irrigation treatments. ADG in irrigated pasture was 0.44 kg/head/day,
83% higher than ADG in non-irrigated pasture. Significant differences in ADG among periods also were detected (P < 0.05); in period one, ADG was 0.62 kg/head/day, three times higher than in periods two and three. In 2000 no differences in ADG were
30 observed between irrigation treatments, which were 0.55 and 0.48 kg/head/day, for irrigated and non-irrigated pastures, respectively. Similar ADG values were detected among periods. Period one was more than 30% higher in ADG than either period two or period three. Beef production in kg per hectare was significantly different (P < 0.05) in
1999 between irrigation treatments with irrigated pastures accounting for 303 kg ha-1, and non-irrigated pasture accounting for 195 kg ha-1. In 2000 no differences between irrigation treatments were observed (P > 0.05).
Coleman and Forbes (1998) investigated the relationship between high, medium and low forage mass and steer average daily gain in Caucasian and Plains Old World bluestems. Pastures were grazed from May to September for two consecutive years.
They observed that steer ADG was significantly higher in the early summer but declined in the late summer as forage supply and nutrients diminished. They found that average daily gain was greater in condition of high and medium herbage mass than in condition of low herbage mass in both summers. In both summers average ADG values were 0.72,
0.70, and 0.52 kg for high, medium and low herbage mass, respectively. Caucasian, moreover, had higher values in ADG and gain per hectare than Plains at all herbage mass levels. Steer performance values were 0.72, 0.81, and 0.55 kg in Caucasian and 0.71,
0.59, and 0.49 kg in Plains for high, medium, and low herbage mass, respectively.
Coleman and Forbes, (1998) suggested that forage availability in Caucasian and Plains pastures should be maintained at approximately 5 or 6 tons per hectare to enhance gain per steer. This amount of forage may be achieved when grass is approximately 40 cm in
31 height. They also suggested that early intensive grazing combined with a high stocking
rate would result in total beef production similar to that achieved by long season grazing.
Ackerman et al., (2001) evaluated the effect of stocking rate on ADG and gain per
hectare. They used light and heavy steers grazing in OWB Plains pasture during the late
spring and summer of two consecutive years. They found that steers ADG was higher in heavy weight steers in both years. ADG ranged from 1.01 to 1.31 kg in the first year and from 0.73 to 0.83 kg in the second year. In contrast, ADG in light steers, it ranged from
0.96 to 1.09 in the first year and from 0.60 to 0.77 kg in the second year. Light weight steers gained more per hectare than did heavy weight steers at all stocking rates in both years. Gain per hectare was more than 220 kg/ha at heavy stocking rates in both groups of steers, in both years. Gain per hectare increased in light weight steers as stocking rate increased over that of heavy weight steers. The authors suggested that there is a potential to enhance gain per hectare by managing different stocking rates of light weight steers, and concluded that Plains Old World bluestem pastures might support higher than traditional stocking rates during summer grazing.
Teague et al. (1996) studied performance of yearling steers in WW-Spar
(Bothriochloa ischaemum) pasture under three levels of standing crop in Vernon, Texas.
They found that average daily gain per head was higher in tall standing crop and lower in
short standing crop. ADG in medium standing crop was similar to tall and short (P >
0.10). ADG was 0.75, 0.69, and 0.64 kg for tall, medium, and short standing crops
respectively. Gain per area was similar in all treatments (P > 0.10) but short treatment
accounted for higher beef production per hectare (129.1 kg). A small difference was
32 observed between effects of medium and tall standing crop; there were 122.9 and 120.0 kg per hectare, respectively.
Cattle performance in response to supplementation.
Feeding supplement to livestock raises many questions about what supplement to use, as well as when, how often, and how much to supplement. Supplemental feed presentation and delivery means are economic issues also being debated (Krysl and Hess,
1993; Huston, 2000). Supplementation involves many expenses, including the cost of the supplement, labor, equipment, and delivery (Bohnert et al., 2002).
Reasons for supplementing cattle include increasing pasture or rangeland carrying capacity, extending forage availability, increasing protein intake, and improving cattle daily weight gain. Other reasons are the provision of a carrier for growth promoters and health enhancers, teaching cattle to eat specific feedstuffs, and facilitating cattle management (Wagner et al., 2000). The primary purpose, however, is to overcome eventual or prevent nutrient deficiencies in forages, or to enhance the effects of high quality forage (Bowman and Sanson 1996).
Supplements contain protein and energy both of which are important in cattle digestion processes. Equilibrium between protein and energy in a supplement is sought
(Bowman and Sanson 1996). Aiken (2002) suggested that high energy or protein supplements are helpful for grazing cattle when seasonal changes in energy and crude protein are present in forages due to environmental factors and plant growth stage.
33 Feeding supplements of high quality forage, grains, and silages may be practical
means to expand available forage or increase stocking rate in a given grazing season or
intensively grazed pasture (Paisley, 2000). In commercial stocker operations, however,
there is still the problem of supplement delivery. Supplements should be formulated to
facilitate its consumption and uniform intake by cattle (Paisley, 2000). Supplements
should be self-limiting or given according to alternate weekly schedules (Roquette et al.,
1992). Huston (2000) found that weekly feeding of supplement to cattle reduces
variability in both forage intake and supplement consumption. Furthermore, adjustment
of supplement levels is recommended throughout the growing season in native
rangelands. Cattle can easily consume small amounts of supplement at the beginning of
the season and then, supplementation may be increased gradually in order to offset
reduction in forage quality (Karn, 2000).
Energy supplements.
Energy supplements are classified according to the type of carbohydrate they contain. Those containing nonstructured carbohydrates have high levels of sugars and starches. Examples are corn, barley, sorghum grains, and molasses-based liquids or blocks. On the other hand, supplements containing structural carbohydrates have high levels of cellulose, hemicellulosa, and lignin. These include soybean hulls, wheat middling, beet pulp, and alfalfa hay (Bowman and Sanson 1996).
Several authors have concluded that energy supplements have an effect on cattle
forage intake. Horn and McCollum (1987) stated that energy supplements tend to reduce
34 forage intake when they contain a high level of starch. Starch decreases utilization of
forages with low protein and high fiber content. Forage intake also is decreased in pastures with high protein content when energy supplements are given, resulting in poor nitrogen utilization because lowered of protein-energy ratio. Owensby et al. (1995) observed that consumption of grain supplements increase the forage standing crop at the end of the grazing season and mention that cattle lessen their forage intake of medium to high quality forages when small amounts of energy supplement are provided. Another study conducted by Aiken (2002) reported that cattle consuming a daily corn ration of 0.4 to 0.6 % of their body weight showed a reduction in in-situ digestibility and organic matter intake when grazing warm-season forage. Horn and McCollum (1987) found that feeding energy supplements of approximately 30 g/kg of metabolic body weight, did not affect forage intake in cattle.
The effect of energy supplements on cattle forage intake and performance has
been associated with the type of carbohydrates in the supplement. Rumen pH is affected
by feedstuff roughage form and type, particle fragmentation, and the buffering capacity
of the roughage per se (Horn and McCollum, 1987). Structural carbohydrates increase
cellulolytic bacteria activity in the rumen, favoring cattle intake and digestibility of low
quality forage. Supplements containing structural carbohydrates enhance positive
associative effect on forage digestion by stabilizing rumen fermentation. In contrast,
nonstructural carbohydrate promotes growth of fibrolytic bacteria in the rumen, which
lower the ruminal pH (less than 6.0) creating unfavorable conditions for cellulolytic
bacteria, depressing fiber digestion, decreasing rate of passage, and reducing forage
35 intake (Bowman and Sanson, 1996; Horn and McCollum, 1987). Consequently,
supplements high in starch have a negative effect on ruminal fermentation. In order to
avoid this effect, feedstuffs with high energy density are recommended. By-product feeds high in fiber, such as wheat middlings, soybean hulls, corn gluten feed, brewer grains, sugar beet pulp, and citrus pulp, meet those requirements (Horn and McCollum,
1987; Horn et al., 1995).
Energy supplements are considered to have a dual function when fed to cattle,
providing a balance between ruminal degradable protein and ruminal fermentable energy,
to facilitate the greatest capture of ruminal degradable protein by microorganisms
(French et al., 2001). Paisley (2000) reported that when the forage dry organic matter digestibility:crude protein ratio (DOM:CP) is below 3:1, deficiency in ruminal energy is
evident, reducing forage nitrogen utilization and resulting in higher concentration of
ruminal ammonia. In this case, feeding energy supplements expand the DOM:CP ratio,
reverting the negative effect.
Different recommendations have been offered in feeding energy supplements to
cattle regarding forage availability and forage quality. Paisley (2000) recommended
feeding energy supplements when forage availability is satisfactory and stocking rate is
increased. In contrast, Horn and McCollum (1987) suggested that energy supplements
are needed to maintain positive cattle performance when forage availability is low and
forage nutrient contents are below animal requirements. Jones et al. (1988) suggested
that feeding a small amount of supplemental grain to cattle that is consuming warm or cold season grass hay enhances production of microbial nitrogen in the rumen. Karn
36 (2000) concluded that supplementing a combination of ground barley and phosphorous
may be favorable for yearling steers in native rangelands, but forage quantity and quality
might influence response to the supplement.
Protein supplements.
Protein supplementation of the diet of cattle consuming forage with less than 6% crude protein in the western United States has been shown to improve animal forage intake and digestibility, weight gain, and reproductive performance (Sprinkle, 2000). In
West Texas it is a common practice to give protein supplements to cattle during pasture
dormancy or seasonal drought (Villalobos et al., 2002).
Many alternative protein supplement formulae exist from which cattle producers
can choose. Most commercial protein supplements are composed of nonprotein nitrogen
and high protein natural feedstuffs (Villalobos et al., 2002). Supplementing protein is
done so that cattle take advantage of low-quality forage. The supplement does this by
feeding ruminal microorganisms, since microbial protein is an essential constituent of
tissues in ruminants (Roquette et al., 1992; Sprinkle, 2000). Ruminants consuming
forage deficient in crude protein are deficient in ruminal nitrogen. This obstructs
microbial growth, resulting in a reduction in ruminal fermentation and nitrogen
absorption in the small intestine (Bohnert, et al., 2002). Cattle weight gain depends on
delivery of amino acids and other energy components to the tissues. Protein content in
the diet delimits the supply of amino acids. Final absorption of amino acids depends on
37 the rate of passage and degree of degradation of crude protein through the rumen to the small intestine and the availability of energy components (Poppi and McLennan, 1995).
Metabolizable protein
There are two types of metabolizable proteins that may influence cattle performance, microbial protein and dietary protein. Microbial protein, known also as degradable intake protein (DIP), is degraded in the rumen. Dietary protein, known also as escape protein or undegradable intake protein (UIP), is provided either by forage or by supplement fed (Paterson et al., 1996). The effect of frequency of feeding metabolizable proteins was studied by Bohnert et al. (2002) in wether lambs. They found that infrequent supplementation of DIP and UIP appear to have minimal effect on the ruminal environment. Fiber digestion, fluid dynamics, and particle passage seem to remain unchanged even when these supplements have different effects on ruminal fermentation and products. They suggested that supplementing rumen degradable protein to cattle improves utilization of poor quality forage, due to rumen fibrolytic bacteria opting for ammonia-nitrogen as a source of nitrogen, thus promoting their growth. This suggests that some proportion of true protein in the rumen can be replaced by nonprotein nitrogen
(Bohnert, et al., 2002; Arroquy et al., 2004). Similar results were observed by Olson et al. (1999) while supplementing DIP in cattle. They observed that supplementing DIP increases intake and digestibility of the forage among cattle grazing tallgrass prairie hay with 4.9% crude protein, although they noted that animal response to the effect of the energy part of the supplement used to deliver DIP remains unclear. Bohnert et al. (2002)
38 concluded that ruminants are capable of efficiently using supplemental nitrogen in the form of DIP or UIP when consuming low quality forage. Bodine and Purvis II (2003) recommended that feeding adequate levels of degradable intake protein aids digestion of supplemental and basal forage diet in cattle that are grazing low quality forage, thus enhancing their performance.
Non protein nitrogen supplements
The effect of non protein nitrogen supplements in cattle was investigated by
Villalobos et al. (2002). They evaluated combinations of biuret and urea with and without implant in heifers grazing dormant WW-B.Dahl pasture. Both supplements contained 32% crude protein; approximately 14% of this was supplied by nonprotein nitrogen sources. In their four treatments, supplement-implant combinations were offered daily at a rate of 0.90 kg/head/day. ADG of heifers in the urea-implant treatment was 53% higher than in the urea-no implant and biuret-implant treatments. Heifers in the biuret-implant treatment also showed better performance than those animals on the urea- no implant and biuret-no implant treatments. The authors concluded that urea-implant combination is a good alternative for non-protein nitrogen supplementation in cattle that are grazing dormant forage.
In order to carry out a protein supplementation program, rangelands and/or improved pastures require adequate availability of forage. McCollum and Horn (1990) suggested that in order to improve cattle performance, protein concentrates were more suitable than energy concentrates in situations where availability of forage is limited.
39 There is strong evidence in favor of feeding protein supplements to cattle when they are
grazing poor quality forage. Pitts et al. (1988) and Villalobos and Britton (1992)
recommended supplementing crude protein to stocker cattle grazing tobosagrass in
winter, spring, and summer when forage protein content is below 7%. Paterson et al.
(1996) and Sprinkle (2000) suggested feeding protein supplement to cattle when forage
quality is less than 7%, in order to improve cattle forage intake and digestibility,
conception rate, and overall performance related profitability in ranching operations.
Frequency in supplement delivery has economic implications. Bohnert et al.
(2002) concluded that ruminants consuming low quality forage can maintain satisfactory performance when protein supplements are provided once a week. Non protein nitrogen sources, however, are not very suitable for infrequent feeding; therefore, a tradeoff between cost of supplement and cost of labor may need to be considered (Villalobos et al.
2002).
Whole cottonseed supplement.
Whole cottonseed has been used in large quantities in feedlot diets in the
Southwestern United States and Northwestern Mexico (Zinn and Plascencia, 1993). In
general, cotton by-products are advantageous feedstuffs in livestock production, but
certain physical and chemical characteristics of gin trash and whole cottonseed limit their
role in cattle diets.
Whole cottonseed has feed value for livestock because of its crude protein and
total digestible nutrient content (Arieli, 1998; Luginbuhl et al., 2000). Its high energy
40 value has been compared with that of steam-flaked corn (3.47 Mcal/kg of ME), which
emanates from its high fat content (23%) (Zinn and Plascencia, 1993). Whole cottonseed, however, contains a polyphenolic yellow pigment called gossypol which has
been reported to have negatively impact reproductive performance of male animals
(Luginbuhl et al., 2000). Zinn and Plascencia (1993) compared whole cottonseed and
steam-flaked corn fed to steers in their growth finishing diet, and found that whole
cottonseed increased by 37% the synthesis of microbial nitrogen. They found also that
the amount of microbial protein increased in the lower digestive tract. Moreover, whole
cottonseed increased lipid postruminal digestion by 4.3% and increased ruminal pH. On the other hand, whole cottonseed decreased ruminal organic matter digestion due to its high fiber content and decreased ruminal N efficiency by 8.0% due to its N ruminal degradability. They found whole cottonseed did not change ruminal volatile fat acid profiles, and the reduction in digestibility was compensated for by reduction of energy lost in the form of ruminal methane.
Morgan (2001) reported that whole cottonseed contains significant amounts of
crude protein and energy to support cattle growth. Evaluation of cotton by-products has
been conducted in steers, dairy cattle, and goats. Zinn (1995) investigated the ruminal
and total tract digestion characteristics of two varieties of cottonseed in Holstein steers,
one a lint free cottonseed and the other a de-linted cottonseed. He found differences that
the lint free had higher crude protein, lipid, and ash content and was lower in ADF than
the delinted seed, although both had similar energy value for cattle growth and
41 maintenance. He observed that lint-free cottonseed was excreted in feces in higher
quantities than was the linted cottonseed.
Villalobos et al. (2000a) studied the effect of whole cottonseed and other energy
supplements on performance of steer grazing a WW-B.Dahl pasture. Corn, whole cottonseed, and no supplement were the treatments during this summer trial. Corn and
whole cottonseed were fed at rates of 0.68 and 0.63 kg/head/day, respectively. Total gain
per head after 87 days was 99, 109, and 107 kg/head for corn, whole cottonseed, and
control, respectively. Although stocking rate was higher in whole cottonseed and corn
treatments than in the control, the total gain per area was 39% and 32% higher in the
whole cottonseed and corn treatments, respectively, than in control. The authors concluded that feeding small amounts of energy supplement to stocker in WW-B.Dahl pasture increases gain per area. In another study, Villalobos et al. (2000b) evaluated starch coated and extruded cotton by-products in steers grazing native rangeland using three treatments: control (no supplement), commercial supplement, and coated and extruded cotton by-product. Supplement treatments were fed at a rate of 0.45 kg/head/day. Results showed that steers fed with commercial supplement and cotton by- product gained 30.4 and 20 kg per head more than the control, respectively. Moreover, the cost to gain an extra pound was 55 and 31 cents per kg for commercial and cotton by- product supplements. They concluded that supplement based on cotton by-products is economically efficient in West Texas rangelands.
42 Methods of estimating forage utilization
Range management relies on the measurement, interpretation, and control of forage plants. Forage utilization has been measured since domestication of herbivores; judgments were ocular and subject to the individual experience of evaluators. The U.S.
Forest Service was the first agency to formally attempt to control forage utilization
(Heady, 1949). Since then, misunderstanding and controversy have been prevalent in issues concerning the measurement and interpretation of forage utilization. Forage utilization or percentage of forage utilized has been used as interchangeable terms. The
Society of American Foresters in 1944 defined forage utilization as “the degree to which animals have removed the current growth of herbage” (Cook and Stoddart, 1953). A more recent definition was provided by the Society for Range Management as “the proportion of the current year biomass production consumed or destroyed by grazing animals” [(Society for Range Management, 1989).]
Estimation of forage utilization is crucial in range or pasture management (Hyder et al., 2003). It provides ranchers and range managers information necessary for decisions about adjusting stocking rate and grazing distribution. Estimates are also necessary in order to measure the effect of grazing on plants and animals (Roach, 1950;
Schmutz et al., 1963; Laycock, et al., 1972; Frost et al., 1994).
Heady (1949) and Hedrick (1958) categorized forage utilization assessment into methods of estimation and methods of measurements. Heady (1949) described and summarized methods of estimating forage utilization by proponent, types of grasses, and locations where evaluations had taken place. He classified methods into estimates
43 (general reconnaissance, ocular estimate by plot, ocular estimate by average of plants, primary forage plant, and utilization by comparison of range with standard photographs) and measurements (weight measurement, conversions of stubble height to weight removed, percent of plant grazed, growth form or height-weight relationship, weight by clipping grazed and ungrazed plots, and stem count). Heady (1949) concluded that each method could be adapted to certain range conditions and degree of range manager expertise. He also noted that all methods might be accurate enough but the interpretation of their results might vary.
Normally, forage utilization is based on current growth ungrazed for a given
period and calculated based on the amount of standing crop (Cook and Stoddart, 1953).
Factors affecting estimation of forage utilization include plant palatability, herbivore
preferences, pasture size and shape, topographic conditions, and water distribution. The
variability and interaction of these factors makes estimation of forage utilization quite
complex.
Different techniques have been developed to measure herbage mass and herbage
consumption by grazing animals, but which methodology is the least labor intensive and
most accurate is still under debate (Hyder et al., 2003). Pechanec and Pickford (1937)
described five methods used in range and improved pasture conditions, discussing
advantages and disadvantages of general reconnaissance, measurement, volume by
weight, stem count, ocular estimate by plot, and ocular estimate by average of plant
methods. They also suggested that methods to estimate forage utilization should be
categorized according to rapidity, accuracy, and adaptability.
44 Grelen (1967) compared three methods of estimating forage utilization in a pine-
bluestem range in Louisiana, using stationary-cage, transient-cage, and plucked quadrat
methods to measure herbage mass and standing crop after grazing. He found that the
transient-cage method showed larger values in herbage yield and utilization than did the
plucked-quadrat method. He recommended using the transient-cage method for
measuring forage production and utilization several times during the year. In another
comparison of forage utilization methods, Laycock et al. (1972) compared esophageal
fistula, paired plots (caged and open), and ocular utilization methods of determining
forage utilization by sheep on a tall-forb range. They found that in the paired plots
method the percentage of forage utilization was higher than it was in the other methods,
adding that this method accounts for the forage consumed and trampled by sheep. They
concluded that the paired plot method is the best for measuring forage utilization on
rangelands, even though it is time consuming.
In improved pastures Sharrow and Motazedian (1983) compared three methods of estimating forage disappearance, the conventional difference method, Linehan et al.’s formula, and Bosch’s formula. They found that the conventional formula tended to overestimate forage disappearance. It was more accurate, however, in the first three weeks of the study, but its accuracy diminished during the stages of rapid forage growth, frequent defoliation, according to the length of the period. Linehan et al.’s formula was more accurate than the conventional method, even though it also overestimated forage disappearance. This formula was less sensitive than the other two to length of periods but was not applicable when forage production was equal to forage consumption. Bosch’s
45 formula tended to underestimate forage disappearance at the beginning of the trial,
showed fairly good accuracy at the middle, and overestimated forage disappearance as
the period of plant protection increased. They found that all methods tended to
overestimate forage disappearance when unclipped reference plots remained protected for
three weeks or more, and they suggested reducing the protection time of these reference
plots.
Methods of estimating forage utilization should be straightforward, accurate, easy
to understand and interpret, and non time consuming to apply (Roach, 1950). Schmutz et
al. (1963) proposed use of the grazed-class method for research and managerial purposes.
This method classified grazed plants into six classes ranging from 0 to 90 percent use.
Additionally, photographic guides and height-weight curves were developed from key
species to guide the examiner in placing grazed plants into their classes. They tested this method against the weight-method in bunchgrass and sodgrass, finding that the grazed- class method was rapid to apply, straightforward, statistically well-founded, and accurate.
They recommended keeping a high degree of correlation between photographic guide, the height-weight curve of the plant used, and the growing form of the plant.
Another method used to estimate forage utilization was applied by Scrivner et al.
(1986), who evaluated the rising plate meter in pastures of subterranean clover (Trifolium
subterraneum L.) and Italian ryegrass (Lolium multiflorum L.) grazed by sheep in a
rotational grazing system. A range of 4 to 12 meter readings were collected in each
pasture before sheep started grazing. After each meter reading, herbage mass was hand
clipped, dried out and weighed, five times over given periods. Linear models of the data
46 were constructed, using forage weight in kg per ha as a dependent variable and meter readings as independent variables. Authors observed a high r2 in all models and observed that the rising plate meter is an accurate range management tool for assessing forage production and its utilization in a rotational grazing system. They noted that the method is comparable to clipping inside and outside cages which are moved frequently.
A conceptual analysis to estimate forage utilization has been proposed by
Scarnecchia (1999), who devised a conceptual analysis defining range utilization and its future implication. His model is called an allocation array and implicitly it includes all variables involved in range utilization estimates.
DSC= scf - sci = g - dng - I - dg where
DSC = change in standing crop (+,0, or -) during the period of calculation. scf = final standing crop (0, or +). sci = initial standing crop (0, or +). g = new growth during the period of calculation (0, or +). dng = disappearance during the calculation period other than that caused by stocked
animals (0, or +). dg = disappearance (trampling losses, etc.) due to stocked animals (0, or +).
I = herbage intake by stocked animals (0, or +).
The author claims that the allocation array is simple to apply and to interpret under rotational grazing systems, and that it can be used also to summarize herbage dynamics in a grazing season or within grazing periods. He suggested that data feeding
47 the allocation array model should come from herbage dynamic models and field
sampling, and pointed out that the typical calculation of forage utilization based on repeated sampling of standing crop involves all variables in the allocation array model.
Modern technology is currently being used to estimate forage utilization. Hyder et al. (2003) developed a forage utilization technique based on digital photography. They applied it to alfalfa (Medicago sativa) plants subjected to six defoliation percentages and two photographic angles. Plants were pictured at 0 and 90° angles and thereafter defoliated at 0, 20, 40, 60, 80 and 100% rates. Forage samples were dried and weighed and simple random coefficient model used to estimate herbage mass removed based on previous plant photograph. Authors found that a combination of photographic angles gave the best estimates of herbage mass in alfalfa plants after defoliation.
Despite the development of many methods to estimate forage utilization, the
effect of grazing animals on plant productivity is not well understood. Problems in over
and underestimation of herbage mass have been pointed out (Singh et al., 1984 cited by
Biondini et al.,1991; Frost et al.,1994; McNaughton et al., 1996). Methods to precisely assess plant compensatory growth have been shown weaknesses by either underestimating or overestimating aboveground net primary production (McNaughton et al., 1996). Frost et al. (1994) stated that forage utilization as it is defined by the SRM implies an overestimation, because it assumes that aboveground net primary production is known. They suggested that forage utilization and its interpretation should be defined for the particular situation in which it is estimated. Forage production in protected plots
which is greater than production in unprotected plots may bias estimations of forage
48 utilization when utilization is computed using the difference between protected and
unprotected plots. This bias could be enhanced when the length of the protection period
is long (Grelen, 1967). Cook and Stoddart (1953) reported that when forage utilization is
estimated by using ungrazed plants as a reference, the percentage of utilization is usually
underestimated compared to use measured by total yield of forage production. They
argue that result of forage utilization studies must be explained considering current
conditions in order to avoid biasing the results. Under irrigated conditions plants exposed
to grazing animals tend to produce more herbage mass than do plants protected by
enclosures. In contrast in arid range conditions plants protected by enclosures may
produce more forage than grazed plants. They argued that forage utilization should be
evaluated considering parts of the plant grazed, plant growing stage, and frequency of
grazing in each growing stage.
The paired-subplot method is another method used to estimate forage utilization
(Bork and Werner, 1999). In this method, one area exposed to defoliation is compared to
a close area protected from defoliation by a cage. Forage use is determined by the
difference between caged and uncaged herbage mass harvested. Data collected from
several random points is averaged and extrapolated to a specific pasture or paddock. The use of this method assumes that aboveground net primary production is the same in caged and uncaged subplots before the grazing event; therefore, any difference between caged and uncaged subplots is due to animal grazing. The method also assumes that neither grazing animals nor cages affect plant growth and that the effects of spatial variability are balanced by using adequate numbers, sizes, and shape of subplots.
49 McNaughton et al. (1996) suggested four alternative methods which could help
reduce error in estimating productivity and consumption in grasslands. They claimed that
the movable-cage method is better than the season-long-cage method because the
movable-cage method takes into consideration compensatory regrowth and leaf turnover,
and factors in species which attain peak herbage mass too soon in the growing season.
The authors identified two sorts of error in the movable-cage method, statistical error and
error in calculating aboveground net primary production. In the first, random errors can
create false pinnacles and depressions, leading to overestimation of forage production. In
the second, negative and positive errors may be produced when calculating the difference
between caged and uncaged plants. Negative errors are detected when compensatory
regrowth is present, resulting in a lower growth rate in cage plots, while positive errors
are observed when grazing limits the capacity of plants to grow, producing higher growth
rates in uncaged plots.
Scrivner et al. (1986) found that shorter periods between caging and clipping reduce differences in forage yield between protected and unprotected plots. They express the relationship of forage production, utilization, and standing crop at the beginning and
end as:
SCe = SCb + G – U
where
SCe = standing crop at the end of the study.
SCb = standing crop at the beginning of the study.
G = total season growth.
50 U = total forage utilization
Other alternatives have been proposed to improve accuracy in estimating forage
utilization. Owensby (1969) studied the effect of cages in True Prairie vegetation near
Manhattan, Kansas. He used wire cages with one square meter of base and 0.75 meter
height. The wire had a mesh of 15.2 x 15.2 cm. Cages were randomly placed during the
fall of 1966 in two ungrazed pastures at three different range sites and clippings were
made inside and outside the cages in the following fall. The author observed 290 kg
more forage production in caged plots and speculated that several factors such as
insolation, humidity, temperature, precipitation intensity, and wind movement influence
forage production between caged and uncaged plots. He noted the importance of recognizing the cage effect in determining forage utilization in grazing studies. In another study, Heady (1957) evaluated the effect of cages in the California annual grassland. His cages were made with 3.8 cm mesh stucco netting of 17 gauge wire 1.0 meter in diameter and 0.76 meter height. Cages were set in ungrazed pastures and measurements taken of botanical composition, plant height, soil surface conditions, and
forage yield during the growing season. He found that a significant plant growth inside
cages during the winter. As soon as temperatures warmed in the spring, however, no plant growth were found between inside and outside the cages.
51 Economic analysis of forage/beef production systems
High farm commodity prices, low interest rates, and low electrical energy costs for pumping water significantly affected the amount of irrigated land in the 1960s and
1970s in the USA. These economic conditions reversed in the early 1980s, putting
irrigated farming in precarious conditions affecting mainly irrigation projects with higher
pumping lifts (Whittlesey and Herrell, 1987).
In the Texas High Plains it is of great concern that underground water is an exhaustible resource and energy costs are increasing. Attempts have been made to project the economic life of irrigation in the region, given the economic implications of the declining availability of water to irrigate land. The eventual depletion of the Ogallala aquifer will shift land use from irrigated cropping systems to dryland cropping systems, strongly affecting the regional economy (Johnson et al., 2004).
Economic models have been proposed to assess the dynamics of the Ogallala
aquifer and their economic impacts on the Texas High Plains region. Hughes and
Harman (1971), cited by Young and Coomer (1979), developed an input-output model
predicting decrement of economic activity in the region due to underground water
depletion. According to their predictions irrigated land in the Texas High Plains will drop to 50.5 thousand hectares in 2015, a dramatic decrease from 1.41 million hectares in
1966. The value of agricultural production is predicted to decline by 70% by Young and
Coomer (1979), considering applications of alternative irrigation methods, cropping patterns, effects of alternative commodities, and energy prices and developing projections of groundwater depletion for the Texas High Plains region.
52 Goss and Shipley (1978) developed a model based on hydraulic principles to
determine depth of the water table, pumping lift, and well characteristics in the region.
Their model integrated economic principles with physical, hydrological, and engineering
relationships, providing a temporal least-cost well system. The model does not, however,
consider the value of water. They claimed that in the Texas High Plains, the cost of
electricity dominates the operational cost of pumping underground water.
Johnson et al. (2004) applied a dynamic optimization model to assess the
economic life of the Ogallala aquifer in the Texas High Plains region, proposing three water conservation scenarios and a baseline scenario without changes in water
conservation polices. They considered water use per unit area, average annual water use,
saturated thickness, annual net income, and net present value. They found that the
scenario restrict underground water withdrawal to 50% of the initial saturated thickness
was the most effective scenario for saving the largest amount of water at the lowest cost.
They added that this water saving alternative is highly flexible for producers, allowing
them to adjust irrigation practices according to environmental conditions.
Terrell and Johnson (1999) evaluated economic impact of underground water depletion from the Ogallala aquifer in the Texas High Plains by applying a dynamic linear programming model to calculate optimal cropping patterns over a 25 year planning horizon. They used an input-output modeling program to assess regional economic impact on agriculture resulting from reductions the supply of underground water for irrigation. They concluded that the region may have to shift from irrigated to dryland agriculture.
53 It is difficult to achieve specific levels of animal production and economic profit
in certain ecosystems. Researchers trying to estimate ecological and economic efficiency
at different input levels have developed computer based analysis tools in the search for
balance in productivity, stability, and sustainability important to beef producers who
which to reduce risk in their enterprises. The main sources of risk are variability in
precipitation, variability in cattle prices, and damage to grassland and soils due to
mismanagement (Hart, 1991). In a livestock/pasture system, the supply of herbage
available to each animal (kg/head) is a function of both the weather and the stocking rate
(Parch et al., 1997). Beef producers must deal with these variations to achieve
production, marketing, and financial objectives of their cattle operations (Riechers et al.,
1989).
Ranchers and farmers apply three basic economic principles to best allocate
available resources. First, they tend to increase the use of inputs as long as the value of
the added output surpasses added cost. Second, they interchange inputs as long as costs
are reduced for a given level of production. Third, they produce at a level which yields
maximum economic return (Clary et al., 1992). Bransby (1989) observed that the economic goal for most pasture based livestock enterprises is to maximize total net
return. Producers tend to maximize return per hectare when land is the factor which most
limits production.
Peel (2000), cited by Phillips et al. (2003), claims that the relationship between
purchase and selling price is the most important factor in determining profitability of the
stocker enterprise, because it determines the value of each kilogram of gain per steer.
54 Ethridge et al. (1987) and Ethridge et al. (1990) stated that stocker production systems
normally purchase cattle in the spring and sell in the fall. Cow-calf operations normally
produce calves in the spring and sell them in fall. This timing facilitates beef production
because during spring and fall rangelands produce both quantity and quality of forage
allowing cattle to gain weight quickly. Cattle prices increase in the spring and decrease
in the fall. The quality of warm season grasses declines in the last part of the summer,
reducing stocker cattle performance through reduction in dry matter digestibility.
Usually, 75% of stocker cattle body weight gain occurs in the first part of the summer
(Phillips et al., 2003).
Brorsen et al. (1983) developed an analytical model for stocker cattle operations
which estimates growth patterns and economic outcomes. It calculates energy
requirements for growth and maintenance, estimates dry matter intake for pasture of
specific qualities by months, projects weights in 5 to 15 day periods, and provides an
economic summary of the projected results. Monthly estimates of quality, protein, and
dry matter availability are obtained for various forages. These estimates along with data
about hay and concentrates are used to calculate the nutritional content of the diet, in
order to estimate stocker gains.
Kreuter et al. (1996) developed the Grazingland Alternative Analysis Tool
(GAAT) which is a computer based decision support software package. It addresses the
complex interactions between ecosystems and herbivores. Even though GAAT has
explain or leave out still remains a good tool for planners, economic analysts, and policy makers involved in the management of grasslands. Another computer software model
55 called GRAZE was used by Parch et al. (1997) with steers grazing bermudagrass pasture
is a computer biophysical simulation model which analyzes the effect of weather
variability on the economic performance of different stocking rate strategies. Based on
14 years of simulated output, results expressed an optimum stocking rate of 6 head/ha.
Ethridge et al. (1987) proposed marketing alternatives to maximize producers
profits in the Southern High Plains/Rolling Plains regions. They constructed a linear
programming model including 48 enterprises and attempted to identify the combination
of enterprises which maximized net revenue high, given average, and low cattle prices.
Enterprises were composed of stocker steers, stocker heifers and three species of grasses.
Other factors were date of purchasing cattle, purchase weight, and date of sale. Forage
production of all grasses was estimated from previous data. The researches found that
under conditions of high and low cattle price net revenue was higher than when cattle
prices were average. They pointed out, however, that income was highly dependent on
the buy-sell price differential. Under average cattle price scenario heifers were allocated
to all pastures, but when cattle prices were high steers grazing Old World bluestem
replaced heifers. Steers also replaced heifers grazing on tobosagrass when cattle prices
were low. Under average and low prices net revenue was $ 64.80 and $81.09 per head
per year respectively. The solution was 65 heifers in bluestem purchased in April 15 with
initial weight of 181 kg and sold in October 15. For high price alternative net revenue
per head per year was $ 15.20. The solution was to stock 282 steers with initial weight of
181 kg from June 15 to August.
56 Ethridge et al. (1987) concluded that stocker cattle operations can improve ranch
profits by combining native rangeland with tame pastures. They recommended that non-
traditional marketing schedules not pegged to seasonal buying and selling patterns should
be considered. In a complementary study, Ethridge et al. (1990) developed procedures to
identify maximum net ranch income from alternative production/marketing systems
given the production and price risks associated with those systems. Cattle prices and
forage production combination were established to conduct the analysis, including nine
combinations of high, normal, and low cattle prices and number of forage production
levels. The analysis considered a ranch with 336 ha of native tobosagrass, 30.3 ha of Old
World bluestem improved pasture, and 30.3 ha of weeping lovegrass improved pasture.
Cattle enterprises consisting of stocker steers, stocker heifers, and a cow-calf operation
grazing those grasses were considered and a linear programming model was used to
determine combinations of enterprises which maximized net returns to the ranch. Results
showed that the expected net return was higher under normal price-normal forage
production combinations in which bluestem was grazed with steers from middle April to
early October and grazed with heifers from early June to the middle of December. In a
high price-high forage scenario, bluestem was grazed by steers only beginning in middle
January and ending in middle October. In a high price-low forage scenario, bluestem was
grazed by steers only from middle January to late October.
The net return per head in stocker steers with initial weight of 181 kg that had grazed bluestem was negative for all purchase-sale dates with the exception of purchasing in October and sale in the middle of July under a low price-low forage scenario.
57 Opposite results were obtained for normal and high buying and selling prices. All net
returns per head were positive under this combination with the exception of the October-
July buy-sell dates. The highest net returns per head grazing bluestem were achieved
under the high-buying price high-selling price scenario. Buying in the middle of January
and selling the first of October accounted for the profit increase per head of $65.85 per
year.
Phillips and Coleman (1995) conducted a three year study to evaluate steer
performance, total gain per area, and input costs in a summer stocker system, using three
different pastures: native tallgrass rangeland with continuous grazing stocking system, a
bermudagrass pasture with rotational stocking system, and an Old World bluestem
pasture composed of Caucasian and Plains grasses managed under a rotational grazing system. They used NEW PASTURE, a spreadsheet program, to calculate profit or loss per head for the stocker enterprise. Forage cost was estimated by dividing the inputs
(fencing, fertilizer, and burning) by the beef production per acre. Other costs considered were equity in steers, interest in cattle purchased, operating capital interest, farm equipment, and the cost of marketing, minerals, and labor. The authors identified principal sources of cost expressed in dollars per head in their experiment. Fertilizer accounted for the largest portion of forage production costs (80%) and interest on money used to purchase cattle (60%) accounted for most of the total production costs. Fencing and fertilizer costs made the total cost of production in bermudagrass and Old World bluestem pastures higher than in native tallgrass range. Expressed as dollars per head,
Old World bluestem pasture production costs were lower than production in native
58 tallgrass range. Old World bluestem pasture allowed a higher stocking rate. When stocker costs are considered, Old World bluestem pasture production cost less than native tallgrass range and bermudagrass pasture production. The three year average of Old
World bluestem net return was $49 /ha at stocking rate of 2.3 head/ha, over 100.3 grazing days. Initial and final body weights were 242 and 297 kg, respectively, indicating that improved warm season pastures support a higher stocking rate than native rangelands, and produce more beef per area. These pastures require greater capital investment even if
30% of the total cost is related to forage production. Phillips and Coleman (1995)
recommended using introduced grasses such as bermudagrass, Caucasian, and Plains because they provide the opportunity for greater positive returns. They suggested
reducing fertilizer applications to reduce cost in forage production and improve the net
return in bermudagrass and Old World bluestem pastures.
Almas (1999) evaluated the economic value of Old World bluestem forage in a
129.5 hectare pasture in Carson County, Texas. Stocker heifers averaging 213 kg live
weight were used in a 112 day summer grazing trial. Two stocking rates were set: high
2.42 and medium 1.58 head per ha. Linear programming models were developed to
assign economic value to the forage and to predict optimal forage utilization. Their
coefficients were estimated from feedstuff normally used in the cattle industry,
calculating the value of dry matter in cents per kg. The Old World bluestem cumulative
forage value at high stocking rate was $125.15 per ha and was $76.93 per ha at medium
stocking rate. Maximizing total weight gain (kg/ha) and total return ($/ha) on Old World
bluestem pasture was the objective of predicting optimal utilization of forage quantity
59 available during each grazing period. Results showed that based on $1.64/kg buying
price and $1.50/kg selling price, total return for the high stocking rate was $181.61/ha
and $102.09/ha for the medium stocking rate.
Phillips et al. (2003) evaluated stocker performance in tallgrass prairie over four
years. Two pastures were grazed all season long at a stocking rate of 2.9 head/ha and two
pastures were half summer grazed with at a stocking rate of 5.9 head/ha. Stockers weight
average was 314 kg. The New Pasture spreadsheet program was used to calculate cost of
production and net profit. In this study, steers gained more weight in the first half of the
grazing season from early June to late July than in the second half from late July to early
August. Good years and poor years coincided with long term rainfall average. The two
first years were good and the second two were poor. Poor years had lower production
costs, but net return per head was -$14.25 and net return per hectare was -$54.86. Good
year net return per head was $11.93 and per hectare $53.35.
Bransby (1989) analyzed three year production data from three bermudagrasses
(Coastal, Callie, and S-16) grazed by steers, assuming that steers were bought and sold at
the beginning and end of the grazing period which lasted on average 151 days each year.
Cultivars were exposed to four grazing pressures with variable stocking rates. One
objective was to study the relation of income to expenses and revenues given stocking
rates and pasture conditions. It was found that higher price differential increased stocking rate at the point where profit per hectare was maximized. In contrast stocking rate decreased with attempts to maximize profit per animal. The stocking rate maximizing profit per animal was less susceptible to changes in price differential. Higher
60 prices differential increased maximum profit because income came from initial animal
weight and weight gained during the grazing period.
Parch et al. (1997) summarized the relationship of stocking rate, animal
performance, and management implications have been extensively studied by range
scientists. In most of their studies light stocking rates had higher average daily gains and
medium or high stocking rates, while producing higher gain per area, entailed higher
risks for producers.
Pearson (1973) noted that grazing studies have revealed that great profits and gain
per area are attained when applying heavy stocking rates for a few years. Large periods of heavy stocking rate, however, reduce herbage production, decrease beef production, and decrease profits over time. Maximum gain per animal normally is attained at light stocking rates but is not often economically practical. Ford (1999) suggested that quality of forage improvement may be evaluated relation to the reduction in grain consumption.
61 CHAPTER III
EFFECT OF LEVELS OF IRRIGATION ON FORAGE STANDING CROP AND
QUALITY IN WW-B.DAHL (Bothriochloa bladhii) PASTURE UNDER SUMMER
GRAZING.
Abstract
Reduction in underground water withdrawals for agricultural purposes is investigated in the Texas High Plains using an Old World bluestem WW-B.Dahl
[Bothriochloa bladhii (Retz) S.T. Blake] grass. Forage standing crop and quality of
WW-B.Dahl were evaluated under three levels of irrigation with summer grazing in
Lubbock County, Texas, for two consecutive summers. Irrigation treatments were High
Irrigation (HI) with 25.4 mm every 10 days; Low Irrigation (LI) with 25.4 mm every 20 days and; No Irrigation (NI). For each summer the study was divided into three periods
of 28 days each, beginning in June 2003 and July 2004, respectively. Precipitation
differed between years: dry conditions were prevalent during 2003 and wet conditions in
2004. Results indicate that forage standing crop was affected (P < 0.05) by level of irrigation and period in both years. Higher yields were observed in LI in 2003 and HI in
2004 with 2,211 kg ha-1and 1,651 kg ha-1 respectively. Level of irrigation affected (P <
0.05) crude protein content in 2004; it was higher in LI with 7.4%. Crude protein was affected (P < 0.05) by period in both years with peaks in July 2003 and August 2004. In vitro dry matter digestibility and neutral detergent fiber were not affected (P > 0.05) by levels of irrigation in 2003 or 2004. In vitro dry matter digestibility results differed (P <
62 0.05) among periods in 2003 and NDF differed (P < 0.05) between periods in 2004.
Forage standing crop of WW-B.Dahl grass appears to be suitable to support moderate grazing pressure during the growing season under average rainfall conditions. In summary, WW-B.Dahl may be a good alternative in the forage/livestock production
system of the region and an alternative to reduce underground water withdrawals from
the Ogallala aquifer.
Introduction
Evaluation of improved pastures seeded with warm season grasses has been
conducted in resent years on the Texas High Plains region. Primary objective is to
increase forage standing crop and quality while using less production inputs, especially
water. Research results showed that Old World bluestems are drought tolerant, grazing resistant, and well accepted by cattle. Also Old World bluestems have high forage potential, high quality in summer, good growth performance in different pH, and good
response to management (Dabo et al., 1987; Hodges and Bidwell, 1993; and McCollum,
2000). Old World bluestems have been seeded on the Texas High Plains since the1920s
(Dabo et al., 1987) and they were released for commercial purposes since the1930s
(Dalrymple et al., 1984). More than two million hectares have been established in Texas
and Oklahoma in the last two decades, bringing great potential to the beef production
system of the region (White and Dewald, 1996; Hodges and Bidwell, 1993). Specifically
WW-B.Dahl, formerly known as WW-857, and most recently released Old World
bluestems have been tested for forage standing crop capabilities under different
63 conditions on the Texas High Plains. Pioneer research with WW-B.Dahl was conducted
by Dahl et al. (1988), Blair et al. (1991), and White and Dewald (1996). More recently,
studies have been conducted by Bezanilla (2002), Villalobos et al. (2002), Philipp (2004), and Allen et al. (2005). The objective of this study was to evaluate forage standing crop,
forage crude protein content, in vitro dry matter digestibility, and neutral detergent fiber
of WW-B.Dahl grass under three levels of irrigation.
Material and Methods
The study was conducted for two consecutive summers, 2003 and 2004, in an Old
World bluestem improved pasture located at the Craig Farm in Lubbock County, Texas.
The study area has an elevation of 993 meters above sea level. Soils are mainly Estacado
clay loam, Lofton clay loam, Portales loam, Randall clay, and Zita loam, with slopes
from 0 to 1% (USDA, 1979).
The climate is classified as semiarid with mild winters and average annual
temperature of 14 °C. The average minimum temperature in January is -3.8° C, and the
maximum in July averages 33.3°C. Most precipitation occurs from April to October with
an annual mean of 433 mm. The growing season is 208 days (National Weather Service,
2005).
A 54 ha WW-B.Dahl pasture was used in this experiment. It was seeded in June
of 1999 and used for grazing experiments since then. Previous to the experiment pasture
was fertilized with ammonia sulfate at a rate of 134.4 kg ha-1.
64 The pasture was divided with electric fences into 12 paddocks ranging in size from 6.0 ha to 3.0 ha. To accomplish the objective three treatments were established to determine the effect of irrigation on forage standing crop and quality. Treatments consisted of High Irrigation (HI), Low Irrigation (LI), and No Irrigation (NI) or dryland condition. The amount of water applied to each treatment was: HI with 25.4 mm every
10 days, LI with 25.4 mm every 20 days, and NI with zero water application. During each summer the irrigation trial was divided into three periods: 32, 28, and 28 days in
2003, and three equal periods of 28 days in 2004. Field data were collected from July to early October in 2003 (88 days) and from June to August in 2004 (84 days).
To estimate the effect of levels of irrigation on forage standing crop and quality,
10 random clippings per paddock per period were carried out using a 0.25 m2 quadrat.
Clippings were conducted every 26 days approximately at the middle of each period.
Herbage was clipped about 2 cm above the soil surface and old material and litter were removed from the samples. Forage samples were dried in a lab at 60 ºC for 72 hours.
Weight was measured to the nearest 0.01 g and recorded. Dried forage samples were ground in a Thomas-Wiley Laboratory Mill™ Model 4 using a 1 mm screen. The ground material was stored in Ziploc plastic bags in a dark dry place prior to laboratory analysis.
Forage standing crop was estimated in kg per ha using the forage dry weight collected from clippings in grams per 0.25 m2. To estimate forage quality a composite of all samples per paddock was carried out. Crude protein content of forage samples was estimated using a LECO CHN-2000 Series Elemental Analyzer (LECO Corp., St. Joseph.
MI). Three replications from the forage sample composite were analyzed. In vitro dry
65 matter digestibility (IVDMD) and neutral detergent fiber (NDF) were determined using
the ANKOM Daisy II incubator (ANKOM Technol. Corp., Fairport, NY) and the
ANKOM-200 Fiber Analyzer (ANKOM Technol. Corp., Fairport, NY), respectively.
Two replications from each composite were used to analyze IVDMD and NDF. To
perform IVDMD analysis rumen fluid was collected from two steers with ruminal fistula.
These steers have been used for experimental purposes in the Texas Tech University
Experimental Facilities in New Deal, Texas. Steers were fed with a diet high in fiber content for two weeks before rumen fluid was extracted. This was collected early in the morning (approximately 700 hrs) each time forage samples were analyzed.
Forage standing crop and forage quality were analyzed as a completely random
design with periods as repeated measures. Due to logistic difficulties with the central
pivot irrigation system, it was not practical to replicate the irrigation treatment.
Therefore, the high irrigation, low irrigation, and no irrigation experimental units used in this research constitute the population of interest. Observation within each treatment
(e.g., the 40 quadrats clipped for forage standing crop estimations were considered as
random samples of their respective population). Statistical inference and interpretation of
results specifically applied to these experimental units (Hurlbert, 1984 and Wester, 1992).
66 Results and Discussion
Distribution of precipitation in the study area
Precipitation measurements were taken in the research site with a farm style rain
gauge. This information was validated with precipitation records from Lubbock
International Airport, located approximately 10 km west from the research site.
Precipitation patterns were atypical in the two-year study (Figure 3.1). During 2003, total
rainfall in the study areas was 148 mm, the lowest in 40 years. Approximately 43% of
the precipitation occurred during spring and early summer, 28% at the beginning of the
summer, 24% in autumn, and 2% in winter. During the length of the experiment in 2003,
July had null precipitation and August and September registered 9.9 and 4.8 mm,
respectively. The long-term average for these summer months is 170.9 mm. The
summer was characterized by a shortage of rainfall with about 8.6% of the long-term
average for the same period. In contrast, in 2004 total rainfall was 844.6 mm, the highest
in the last 60 years. Precipitation distribution was 17.5, 25.8, 43.2, and 13.4% for spring,
summer, autumn and winter, respectively. Rainfall during the period of study was 78.2,
81.8, and 58.2 mm for June, July, and August respectively. The long-term average for
these months is 177 mm. Therefore, rainfall during the length of the experiment
accounted for approximately 20% higher than the long-term average in the same period.
September and November were characterized by the highest precipitation with 136 and
169 mm respectively. Temperatures were similar in both 2003 and 2004. They also
followed the long-term average for the region (Figure 3.2).
67 Total water availability (irrigation plus rainfall) during the irrigation trial in 2003
was 192.5, 116.3, and 14.7 mm for HI, LI, and NI treatment, respectively (Table 3.1). In contrast, water availability in 2004 was significantly higher with 396.0, 319.8, and 218.2 mm for HI, LI, and NI treatment respectively (Table 3.2).
Forage standing crop
Significant irrigation effect, period effect, and irrigation-period interaction were
detected in forage standing crop in 2003 (Table 3.3). Due to the irrigation-period
interaction means separation was analyzed holding one factor constant. When forage
standing crop means were analyzed within periods, differences were detected in July and
September. During July LI and NI had similar values, having in average 1,294 kg ha-1
more forage standing crop than HI. In September forage standing crop was similar in HI
and LI, and similar values were observed in LI and NI too. In HI had the highest forage
standing crop and in NI the lowest, differing between them in more than 500 kg ha-1 of
herbage mass. In contrast, during August irrigation had no effect in forage standing crop.
When forage standing crop means were compared within irrigation, differences were
detected in all levels of irrigation. In HI, August and September had similar values in
forage standing crop, having more than 370 kg ha-1 more in herbage mass than July. In
LI, herbage mass was different in all periods, decreasing from July to September. July had the higher forage standing crop, differing for more than 1,370 kg ha-1 of herbage
mass from September, in which was the lower forage standing crop observed. Similar
tendency was noticed in NI; all periods differed between each other in forage standing
68 crop. The higher forage standing crop was detected in July, being more than 1,320 kg ha-
1 higher than September, in which had the lowest yield. Summarizing results from 2003,
data suggested that the irrigation effect in HI treatment was evident. For example, forage
standing crop in HI tended to increase from July to August and marginally decreased
from August to September. In LI and NI forage standing crop showed a decreasing
tendency along periods.
During 2004 results detected are presented in Table 3.4. Similar results were
observed as for the previous year in irrigation effect and factor interaction. During this
year, irrigation had an effect on forage standing crop and no difference was observed
among periods. An interaction was observed between irrigation and period. Once again
due to factor interaction detected means separation was analyzed holding one factor
constant. When forage standing crop means were analyzed within periods, differences
were detected in July and August. During July, forage standing crop in HI was higher,
differing from LI and NI. Forage standing crop was more than 800 kg ha-1 higher in HI
than in LI and NI. During August, HI and LI had similar values, having in average more
than 557 kg ha-1 more yield than NI. In contrast, June irrigation had no effect on forage
standing crop. When forage standing crop means were compared within irrigation, differences were detected in HI and LI treatments. In HI, forage standing crop in July
differed from June and August. Forage standing crop in July was more than 260 kg ha-1 higher than June and August. In contrast, in LI similar values in forage standing crop were detected in June and August, differing from July yield. On average, forage standing crop in June and August was 347 kg ha-1 higher than July yield. During NI treatment in
69 all periods similar values were detected. Results from 2004 suggested that forage standing crop in HI increased from June to July, having marginal reduction from July to
August. In contrast, in LI, forage standing crop decreased from June to July, having significant increment from July to August, but in NI a decreasing tendency was observed in forage standing crop as the growing season advanced.
In 2003, results on average showed that forage standing crop was higher in LI and quite similar in NI and HI. However, water availability during the length of the study between HI and NI was diametrically different with 193 and 14 mm, respectively. But forage standing crop among periods showed a reasonable pattern, with yield decreasing as the growing season advanced, showing approximately 400 kg ha-1 in forage standing crop reduction among periods. In contrast, during 2004 moisture conditions were favorable; average annual rainfall was 5.7 times that of 2003. Therefore, water availability in levels of irrigation in 2004 was higher than observed in 2003. During
2004, results showed the expected outcome in forage standing crop, having higher forage standing crop in better soil moisture conditions. On average the data suggested that forage standing crop increased as water availability increased in 2004. In addition, water availability among periods was less critical in 2004 than those registered in 2003.
Condition of uniformity in water availability during the growing season may explain the narrow differences observed in forage standing crop among periods in 2004.
In general, data suggest that forage standing crop in 2003 and 2004 was below the average per hectare revealed from previous studies in Lubbock County by Bezanilla
(2002), Villalobos et al. (2002), and Philipp (2004), who reported approximately 4.0, 5.8,
70 and 2.4 thousand kg per hectare, respectively. Forage standing crop under dryland conditions fell in the range mentioned by McCollum (2000), from 0.5 to 3.0 thousand kg per hectare. Low yield in forage standing crop in this study may be related to the amount and distribution of precipitation during 2003, affecting plant growth in both years.
Precipitation during 2003 was 38% below the long term average, being low during summer and fall. The precipitation shortage during the growing season of 2003 stressed the effect of irrigation in forage standing crop in HI. In this treatment forage standing crop increased near 40% from July to August and decreased 11% from August to
September; but, water availability along the period was near 193 mm, of which 70% came from irrigation. On the other hand, dramatic forage standing crop reduction was observed under LI and NI as the growing season advanced.
Even when reduction in herbage mass was evident in LI and NI due to reduction in water availability in 2003, WW-B.Dahl continued showing growth under water stress conditions. Further, this herbage growth may be attributed to precipitation in fall 2002 and spring 2003. This is supported by Philipp (2004), who mentioned that soil moisture content from precipitation during fall 2002 accounted for the biomass accumulation in the
Old World bluestem grasses that he evaluated during summer 2003. Additionally, the effect of grazing may enhance WW-B.Dahl growth in this study, increasing water use efficiency as mentioned by Brown (1995), Svejcar and Christiansen, (1987) and Masters and Britton, (1988) that suggested that defoliation seems to enhance water use efficiency in this Old World bluestem, letting grasses continue growth under limited moisture conditions. Similar response in herbage growth under poor moisture conditions in
71 Bothriochla specie had been reported by Coyne et al. (1995), Owensby et al.(1999) and
Derner et al.(2000). Even when leaf:stem ratio was not measured in this study biomass
accumulation in 2003 in poor moisture conditions may have related with Philipp (2004)
findings. He reported that leaf:stem ratio increased in WW-B.Dahl, Caucasian, and Spar
grasses under dryland conditions in New Deal, Texas.
Results of this study from two consecutive summers in which moisture conditions
widely varied suggest that herbage growth in WW-B.Dahl is linked to morphological and
physiological aspects of the plant rather than water availability. Data from this study also
show that WW-B.Dahl has the ability to perform under extreme moisture conditions; however, rainfall conditions during fall seemed to affect forage production potential in the following growing season.
Forage Quality
Crude Protein
No irrigation effect in forage crude protein content was observed in 2003, but
difference was observed among periods. In addition, an irrigation-period interaction was
detected (Table 3.5). Because of the interaction, means separation analysis was
performed within levels of irrigation and within periods. When crude protein means were
analyzed within periods, a difference in crude protein content was observed only in
September. Results from this period showed that crude protein content was higher in LI,
differing from HI and NI in which values were similar. In contrast, no differences were
detected in July and August within periods. When crude protein means were compared
72 within irrigation, differences were detected in HI and NI treatments. In both treatments differences were detected across periods and followed similar pattern. The highest value
was observed in July and the lowest in September. In contrast, in LI no difference was
observed, having slight variation between values. Yet, September showed the highest
value and August the lowest.
During 2004 irrigation had effect on crude protein opposite to the previous year.
In 2004 period effect and irrigation-period interaction were observed similar to the 2003 results (Table 3.6). Due to the interaction means separation analysis was performed
within levels of irrigation and within periods. When crude protein means were analyzed
within periods, differences were observed in all periods. A similar pattern was noticed in mean separation in June and August in all treatments. In both periods, LI and NI showed the higher and similar values. In contrast, in July LI showed the highest crude protein value, differing from HI and NI, which were similar.
Results from forage crude protein content in 2003 suggested that the lack of
rainfall during the length of the study had no effect in WW-B.Dahl forage quality.
Hence, rainfall during this period was 14.7 mm. Data from forage crude protein content
appeared not disperse in this study in 2003, therefore was difficult to identify a pattern.
These results agreed with Buxton (1996), who reported that there is no consistent pattern
in crude protein content due to water stress in grasses. Even though no pattern was
identified due to irrigation, a consistent decreasing tendency in crude protein was
observed as the growing season progressed. This pattern agrees with results from Almas
73 (1999). He observed that the crude protein content in Old World bluestem decreased as the growing season progressed.
Due to drought conditions registered during the first year of study, large
differences in crude protein values between irrigated treatments and dryland treatment
were expected. On average total water availability for HI, LI, and NI was 79.2, 38.7, and
14.7 mm, respectively. Difference in crude protein values among treatments was not
significant. Thus, the relatively acceptable level of protein in WW-B.Dahl under dryland
conditions may be explained by the mechanisms that plants possess to tolerate water
stress (Deetz et al. 1996; Ranieri et al. 1989; Jaing and Huang 2002).
Data from 2004 in crude protein content were more dispersed than those observed the previous year. Further, rainfall during the length of study was approximately 15 times higher than rainfall in 2003 during the same period. Crude protein data in 2004
showed that HI treatment had the lowest values in all periods, but total water availability
in this treatment was 25 to 50 mm higher than total water availability in LI and NI
treatments, respectively. These results are in agreement with Philipp (2004). He found
that as soil moisture content increased leaf:stem ratio decreased, reducing crude protein
content in WW-B.Dahl. The magnitude of the difference in crude protein content among
treatments was larger between HI and LI treatments than between LI and NI. The same
pattern is reported by Philipp (2004). During the first year of evaluation, crude protein
decreased as the growing season advanced, in contrast to the second year crude protein
content decreasing from June to July and increasing from July to August. Similar results
74 were reported by Philipp (2004) in WW-Dahl evaluated under different moisture
gradients and Asay et al. (2002) in tall fescue subjected to different irrigation levels.
The conclusion is that forage crude protein content in WW-B.Dahl is not greatly influenced by either dry or moist conditions in summer, but changes in crude protein content are not well defined as growing season progresses.
In Vitro Dry Matter Digestibility
In vitro dry matter digestibility (IVDMD) was not affected by levels of irrigation
in 2003 (Table 3.7), but differences among periods were seen. In 2003, August had the
higher IVDMD value, showing lower values in July and September. Results in IVDMD
during 2004 are shown in Table 3.8. The irrigation effect was similar to the previous
year differences in which were not detected.
Results from in vitro dry matter digestibility in both years of study showed similar
pattern. Within years, IVDMD values were similar in both levels of irrigation and
periods. Negligible changes in IVDMD values were observed among irrigation treatments. During both years NI showed slightly higher IVDMD values. It is important to notice that during 2003 and 2004 IVDMD, values showed similar patterns, increasing from the first to the second period and decreasing from the second to the third. This pattern contradicts many studies conducted in Old World bluestem and other grasses. In these studies IVDMD showed a decreasing tendency as the growing season progressed regardless of soil moisture and grazing conditions (Dabo et al., 1987; Almas, 1999; Asay et al. 2002; and Philipp, 2004). Even though leaf:stem ratio was not measured in this
75 experiment, it was hypothesized that the pattern in IVDMD observed in WW-B.Dahl was
affected by animal grazing. Continuous defoliation may have improved the leaf:stem
ratio and increased the total digestible nutrients in the regrowth as reported by Linn and
Martin (1999), Svejcar and Christiansen (1987), and Masters and Britton (1988) in Old
World bluestem grasses. From direct field observations during the both summers of
evaluation, WW-B.Dahl did not show rapid change from growing stage to reproductive
stage while it was grazed. The presence of seedheads was more evident after grazing was
removed in early October in 2003 and early September in 2004.
Dry matter digestibility values were lower in 2003 than 2004. These percentages
of IVDMD in WW-B.Dahl apparently are high if considering drought conditions in 2003.
These apparently high IVDMD values in 2003 are in agreement with Buxton (1996), who suggested that forage plants exposed to drought stress and minimal heat stress conditions could improve their digestibility. During the period of this study in 2003, temperatures in
July and August were slightly above the long term average. Higher IVDMD values detected in 2004 may be explained by the higher rainfall, relative humidity, and soil moisture prevalent during the summer of that year, agreeing with the Pitman and Holt
(1982) findings in kleingrass, plains bristlegrass, and green sprangletop.
In vitro dry matter digestibility in WW-B.Dahl was not affected by level of
irrigation in this study. Changes in IVDMD percentages did not follow a pattern in
relation to changes in grass maturity stages. However, data from the second year of study
suggested that favorable rainfall conditions tend to improve IVDMD in WW-B.Dahl.
76 Neutral Detergent Fiber
Values in neutral detergent fiber (NDF) are opposite from IVDMD values. NDF
indicates the non digestible parts of the plant. Results from NDF in 2003 were similar to
IVDMD result in the same year (Table 3.9). Results showed no difference among levels
of irrigation but differences among periods. On average, NDF values among levels of
irrigation were similar. In contrast, periods were different with and similar NDF values
in July and September and lower in August.
During 2004 NDF results followed the same pattern as those observed in IVDMD
in the same year (Table 3.10). No significant differences were detected between
irrigation and period. On average, NDF values were higher similar in HI and LI and
lower in NI. Percentages of NDF among periods also were very similar.
Overall results in NDF in WW-B.Dahl in this study coincide with the conclusion
drawn by Jensen et al. (2003) and Asay et al. (2002) in their studies with orchargrass,
ryegrass, and tall fescue under different irrigation gradients. They reported negligible
changes in NDF among irrigation gradients and time.
Conclusions
Results presented in this study suggest that forage standing crop of WW-B.Dahl grass is affected by levels of irrigation, but the effect was not consistent with the amount of water available. Grass growth response to water stress is noticeable. Regarding forage quality, results showed that under limited water availability CP content in WW-B.Dahl is not affected. Under abundant water availability conditions CP tended to decline. Other
77 quality parameters evaluated were IVDMD and NDF, which were not affected by levels
of irrigation. There is no clear pattern in the effect of WW-B.Dahl growing stage in these parameters. WW-B.Dahl may be a good alternative in the forage/livestock production system of the region and a feasible alternative in reducing underground water withdrawal from the Ogallala aquifer.
78
2002 2003 2004 Long-term
180
160
140 120
100 80
60 Precipitation (mm) 40
20 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month
Figure 3.1. Precipitation monthly average in Lubbock County, Texas in 2002, 2003, 2004, and 30 years long-term average.
79
2003 2004 Long-term
30
25
20
15
Temperature (ºC) Temperature 10
5
0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month
Figure 3.2. Temperature monthly average in Lubbock County, Texas in 2003, 2004 and 30 years long-term average.
80
Table 3.1. Water availability (mm) by level of irrigation and period in study conducted in WW-B.Dahl (Bothriochloa bladhii) pasture grazed in summer 2003 in Lubbock County, TX.
Treatment High Irrigation Low Irrigation No Irrigation Period Rain Irrigation Rain Irrigation Rain Irrigation
------mm------
July 0.0 25.4 0.0 25.4 0.0 0.0
August 9.9 76.2 9.9 50.8 9.9 0.0
September 4.8 76.2 4.8 25.4 4.8 0.0
Subtotal 14.7 177.8 14.7 101.6 14.7 0.0
Total 192.5 116.3 14.7
81
Table 3.2. Water availability (mm) by level of irrigation and period in study conducted in WW-B.Dahl (Bothriochloa bladhii) pasture grazed in summer 2004 in Lubbock County, TX.
Treatment High Irrigation Low Irrigation No Irrigation Period Rain Irrigation Rain Irrigation Rain Irrigation
------mm------
June 78.2 50.8 78.2 25.4 78.2 0.0
July 81.8 76.2 81.8 50.8 81.8 0.0
August 58.2 50.8 58.2 25.4 58.2 0.0
Subtotal 218.2 177.8 218.2 101.6 218.2 0.0
Total 396.0 319.8 218.2
82
Table 3.3. Effect of levels of irrigation on forage standing crop in WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003.
Period
Treatment July August September Mean
------kg ha-1------
High Irrigation 1,483B1b2 2,075Aa 1,855Aa 1,804
Low Irrigation 2,910Aa 2,187Ab 1,536ABc 2,211
No Irrigation 2,644Aa 1,625Ab 1,315Bb 1,861
Mean 2,345 1,962 1,569
1 Irrigation means within a period followed by the same upper case letter are not significant different (P > 0.05, LSD). 2 Periods means within an irrigation followed by the same lower case letter are not significant different (P > 0.05, LSD).
83
Table 3.4. Effect of levels of irrigation on forage standing crop in WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004.
Period
Treatment June July August Mean
------kg ha-1------
High Irrigation 1,477A1b2 1,869Aa 1,606Ab 1,651
Low Irrigation 1,333Aa 1,023Bb 1,407Aa 1,254
No Irrigation 1,180Aa 1,018Ba 949Ba 1,049
Mean 1,330 1,303 1,321
1 Irrigation means within a period followed by the same upper case letter are not significant different (P > 0.05, LSD). 2 Periods means within an irrigation followed by the same lower case letter are not significant different (P > 0.05, LSD).
84
Table 3.5. Effect of levels of irrigation on forage crude protein content in WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003.
Period Treatment July August September Mean ------%------High Irrigation 6.2A1a2 5.7Ab 4.9Bc 5.6 Low Irrigation 5.6Aa 5.4Aa 6.0Aa 5.7 No Irrigation 6.0Aa 5.5Ab 4.5Bc 5.3 Mean 6.0 5.5 5.1
1 Irrigation means within a period followed by the same upper case letter are not significant different (P > 0.05, LSD). 2 Periods means within an irrigation followed by the same lower case letter are not significant different (P > 0.05, LSD).
85
Table 3.6. Effect of levels of irrigation on forage crude protein content in WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004.
Period Treatment June July August Mean ------%------High Irrigation 6.2B1a2 5.1Bb 6.1Ba 5.8 Low Irrigation 7.3Ab 6.7Ac 8.1Aa 7.4 No Irrigation 7.1Ab 5.5Bc 8.6Aa 7.1 Mean 6.9 5.8 7.6
1 Irrigation means within a period followed by the same upper case letter are not significant different (P > 0.05, LSD). 2 Periods means within an irrigation followed by the same lower case letter are not significant different (P > 0.05, LSD).
86
Table 3.7. Effect of levels of irrigation on forage in vitro dry matter digestibility (IVDMD) in WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003.
Period Treatment July August September Mean ------%------High Irrigation 66.8 67.1 65.6 66.5a1 Low Irrigation 66.9 67.8 64.6 66.4a No Irrigation 63.2 72.8 65.4 67.1a Mean 65.6B2 67.5A 65.2B
1 Irrigation means followed by the same lower case letter are not significant different (P > 0.05, LSD). 2 Periods means followed by the same upper case letter are not significant different (P > 0.05, LSD).
87
Table 3.8. Effect of levels of irrigation on forage in vitro dry matter digestibility (IVDMD) in WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004.
Period Treatment June July August Mean ------%------High Irrigation 72.2 73.3 72.0 72.5a1 Low Irrigation 72.5 73.4 71.9 72.6a No Irrigation 72.3 73.7 73.7 73.2a Mean 72.4 A2 73.5A 72.5A
1 Irrigation means followed by the same lower case letter are not significant different (P > 0.05, LSD). 2 Periods means followed by the same upper case letter are not significant different (P > 0.05, LSD).
88
Table 3.9. Effect of levels of irrigation on forage matter neutral detergent fiber (NDF) in WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003.
Period Treatment July August September Mean ------%------High Irrigation 33.2 32.8 34.3 33.4a1 Low Irrigation 33.4 31.3 35.0 33.2a No Irrigation 36.8 27.3 34.8 33.0a Mean 34.4A2 30.51B 34.7A
1 Irrigation means followed by the same lower case letter are not significant different (P > 0.05, LSD). 2 Periods means followed by the same upper case letter are not significant different (P > 0.05, LSD).
89
Table 3.10. Effect of levels of irrigation on forage neutral detergent fiber (NDF) in WW- B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004.
Period Treatment June July August Mean ------%------High Irrigation 27.7 26.6 27.9 27.4a1 Low Irrigation 27.4 26.6 28.1 27.3a No Irrigation 27.6 26.2 26.0 26.6a Mean 27.6A2 26.5A 27.3A
1 Irrigation means followed by the same lower case letter are not significant different (P > 0.05, LSD). 2 Periods means followed by the same upper case letter are not significant different (P > 0.05, LSD).
90 References
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Almas, L.K. 1999. Economic evaluation for old world bluestems in the Texas Panhandle. Dissertation. Texas Tech University. Lubbock, TX. 134 p.
Ankom, T. 2000. In vitro true digestibility using DAISYII incubator. ANKOM Technology
Ankom, T. 2000. Method for determining neutral detergent fiber (NDF). ANKOM Technology
Asay, K. H., K. B. Jensen, B. L. Waldon, G. Han, D. A. Johnson, and T. A. Monaco. 2002. Forage quality of tall fescue across and irrigation gradient. Agronomy Journal 94:1337-1343.
Bezanilla, A.G. 2002. Effect of irrigation and grazing systems on steer performance and plant response in an old world bluestem pasture. Texas Tech University. Master Thesis. 56 p.
Blair, K.B., C.Villalobos, R. Tower, and C.M. Britton. 1991. Evaluation of WW-857 at the Texas Tech Experimental Ranch. p. 21-22. In Research highlights. Dep. Range Wildlife Mgt., Texas Tech University., Lubbock.
Brown, R. W. 1995. The water relations of range plants: Adaptations to water deficit. Society for Range Management. Bedunah, D. J. and R. E. Sosebee. Editors
Buxton, D. R. 1996. Quality-related characteristics of forage as influenced by plant environment and agronomic factors. Animal Feed Science Technology. 59:37-49.
Coyne, P. I., M. J. Trlica, and C. E. Owensby 1995. Carbon and nitrogen dynamics in range plants. Society for Range Management. Bedunah, D. J. and R. E. Sosebee. Editors.
Dabo S. M., C. M. Taliaferro, S.W. Coleman, F.P. Horn, and P.L. Claypool. 1987. Yield and digestibility of old world bluestem grasses as affected by cultivar, plant part, and maturity. J of Range Manage 40:10 15
91 Dahl, B.E., H.D. Keesee, and J.S. Pitts. 1988. Old world bluestems for west Texas. p. 21-22. In Research highlights. Dep. Range Wildlife Mgt., Texas Tech University., Lubbock.
Dalrymple, R.L., J. Rogers, and L. Timberlake. 1984. Old world bluestem comparison. Agricultural Division, Noble Foundation, Ardmore OK. Report AB-84
Deetz, D. A., H. G. Juang, and D. R. Buxton. 1996. Water-deficit effects on cell-wall composition and in vitro degradability of structural polysaccharides form alfalfa stems. Crop Sci 36:383-388
Derner, J. D., H. W. Polley, H. B. Johnson, and C. R. Tischler. 2001. Root system response of C4 grass seedlings to CO2 and soil water. Plant and Soil 231:97-104.
Hodges, M. and T.G. Bidwell. 1993. Production and management of old world bluestems. Oklahoma Cooperative Extension Service. Division of Agricultural Sciences and Natural Resources F 3020.
Hurlbert, S.H. 1984. Pseudoreplication and the design of ecological field experiments. Ecological Monographs. 54:187-211.
Jensen, K. B., B. L. Waldron, K. H. Asay, D. A. Johnson, and T. A. Monaco. 2003. Forage nutritional characteristics of orchardgrass and perennial ryegrass at five irrigation levels. Agronomy Journal 95:668:675
Jiang, Y. and B. Huang. 2002. Protein alterations in tall fescue in response to drought stress and Abscisic Acid. Crop Sci. 42:202-207.
LECO Co. 2005. Nitrogen in plant tissue. Organic application notes. LECO Corporation.
Linn, J. G. and N. P. Martin. 1999. Forage quality test and interpretations. Minnesota Extension Service, University of Minnesota, AG-FO-2637, St. Paul.
Masters, R.A. and C.M. Britton. 1988. Response of WW-517 old world bluestem to fertilization, watering, and clipping. Texas Journal of Agriculture and Natural Resources. 2:48-53.
McCollum, T. 2000. Old world bluestem pasture management strategies. Plains Nutritional Council Fall Grazing Conference. Texas A&M University. Agricultural Research and Extension Center, Amarillo, TX. Publication No. AREC 00-45. pp 11-17.
92 National Weather Service. 2005. http:// www.srh.noaa.gov/lub/climat. [Accessed Friday March 18, 2005].
Owensby, C. E., J. M. Ham, A. K. Knapp, and L. M. Auen. 1999. Biomass production and species composition change in a tallgrass prairie ecosystem after long-term exposure to elevated atmospheric CO2. Global Change Biology 5:497-506.
Philipp, D., 2004. Water use efficiency and nutritive value of three old world bluestems.(Bothriochloa spp) Disseratation. Texas Tech University. Lubbock, TX. 195 p.
Pitman W.D. and E. C. Holt. 1982. Environmental relationship with forage quality of warm-season perennial grasses. Crop Science. 22:1012-1016.
Ranieri, A., R. Bernardi, P. Lanese, and G. F. Soldatini. 1989. Changes in free amino acid content and protein pattern of maize seedling under water stress. Environmental and Experimental Botany. 29:351-357.
Svejcar, T. and S. Christiansen. 1987. Grazing effect on water relationship of caucasian bluestem. Journal of Range Management. 40 (1) 15-18.
United States Department of Agriculture.1979. Soil Survey of Lubbock County Texas.. Soil Conservation Service in cooperation with Texas Agricultural Experimental Station.
Villalobos, C., M. Avila, G. Bezanilla, and C.M. Britton. 2002. Cattle performance grazing WW-B.Dahl old world bluestem with different sources of protein supplementation. p. 23-24. In Research highlights. Dep. Range,Wildlife, & Fisheries Mgt., Texas Tech University., Lubbock.
Wester, D.B. 1992. Viewpoint: Replication, randomization, and statistics in range research. J. of Range Manage. 45:285-290.
White, L. M. and CH. L. Dewald. 1996. Yield and quality of WW-Iron Master and caucasinan bluestem regrowth. J. Range Manage. 49:42-45.
93 CHAPTER IV
EFFECT OF LEVELS OF IRRIGATION ON PERFORMANCE OF STEERS
GRAZING A WW-B.DAHL (Bothriochloa bladhii) PASTURE DURING THE
SUMMER
Abstract
Forage production capabilities of WW-B.Dahl [Bothriochloa bladhii (Retz) S.T.
Blake] were investigated to enhance beef production on the Texas High Plains. Steer
performance was evaluated in Lubbock County, Texas. The grazing trial was conducted in 54 hectares of WW-B.Dahl pasture divided into 12 paddocks. Three levels of irrigation and two levels of supplement were established. Irrigation treatments were:
High Irrigation (HI) (25.4 mm every 10 days); Low Irrigation (LI) (25.4 mm every 20 days) and; No Irrigation (NI). Levels of supplement were (S) (0.454 kg of whole cottonseed/head/day) fed three times a week and no supplement (NS). Grazing trial was conducted for two consecutive summers, divided in three equal periods starting in July
2003 and June 2004. A 142 steers with average weight of 181.0 kg (SD ± 30.7 kg) in
2003 and 108 steers with average weight of 214.9 kg (SD ± 26.2 kg) in 2004 were used.
Results suggested that average daily gain and gain/ha were not affected (P > 0.05) by irrigation in both years. ADG and gain/ha were affected by period (P < 0.05) in both years. ADG was affected by supplement only in 2004 (P < 0.05). No supplement effect was observed in gain/ha in both years. Among periods ADG was higher in August 2003 and June 2004 peaked with 0.94 and 1.18 kg/head/day, respectively. In 2004
94 supplemented steers showed higher ADG than unsupplemented. Among periods gain/ha
had similar pattern that ADG. Forage standing crop and quality of WW-B.Dahl appeared to be sufficient to maintain satisfactory steer performance regardless of moisture conditions during the growing season. It seems that with higher precipitation during the growing season ADG and gain per ha could be improved when feeding whole cottonseed to steers.
Introduction
Old World bluestem grasses are gaining more attention among beef producers,
range scientists, and land managers. As a result in the last decades several thousand
hectares have been established on the High Plains (White and Dewald, 1996). It is
expected that Old World bluestem grasses may contribute in designing forage/livestock
systems with less demand for water (Philipp, 2004) enhancing the beef production
potential of the region (Hodges and Bidwell, 1993). Recently in the Texas High Plains
region Old World bluestem pastures have been incorporated into the beef production
systems, increasing farmer income in which cotton and wheat show low rates of return
(Allen et al., 2005; Hodges and Bidwell, 1993; Wang et at., 1992). At the same time
grazing trials have been conducted to evaluate the forage potential of WW-B.Dahl.
Bezanilla (2002) studied the effect of levels of irrigation and grazing system in WW-
B.Dahl pastures in Lubbock, County. His results showed that average daily gain and total beef production in kg per hectare were higher in irrigated pastures in the first year of
study. No differences in the second year were observed in the same parameters. The
95 effect of supplement also has been evaluated in WW-B.Dahl during growing and
dormancy seasons. Villalobos et al. (2000) evaluated the effect of whole cottonseed,
corn, and no supplement in steer performance during summer. Results showed that total
gain per area was 39 and 32% higher then the control when steers were supplemented with whole cottonseed and corn respectively than the control. Another study at the same
site was conducted by Villalobos et al. (2002). They used non protein-nitrogen (NPN) as
a source of protein supplement. They evaluated urea and biuret in heifer performance in
dormant WW-B.Dahl pasture. Their treatments were a combination of NPN supplement
and implant. Results showed that ADG was 53% higher in urea-implant treatment. They also observed satisfactory cattle performance in biuret-implant treatment. Lower ADG was reported in urea-no implant and biuret-no implant treatments.
Further research by Guillen and Berg (2001) and Kloppenburg et al. (1995)
evaluated cattle performance in native rangelands and Old World bluestems and
bermudagrass pastures. These studies were aimed to take advantage of spring growth in
native grasses and summer growth of warm season grasses reducing variability in forage
production and quality as well as reducing grazing pressure in native rangelands.
From previous information it seems that WW-B.Dahl has potential in the
livestock industry of the Texas High Plains. Evaluation of cattle performance in WW-
B.Dahl pastures is continuing. Objective of this study was to evaluate steer performance
grazing a WW-B.Dahl pasture during summer. ADG and gain per area in terms of kg per
hectare were measured under three levels of irrigation and two levels of whole cottonseed as a source of energy supplement.
96
Material and methods
Performance of yearling stockers grazing a WW-B.Dahl pasture was evaluated
under three levels of irrigation and two levels of whole cottonseed supplement in summers of 2003 and 2004. Crossbred Bos taurus x Bos indicus steers were used in this
study. Experimental animals used were 142 steers with initial average weight of 181.0 kg
(SD ± 30.7 kg) in 2003 and 108 steers with initial average weight of 214.9 kg (SD ± 26.2
kg) in 2004. The study was conducted at Craig Farm in Lubbock County, Texas. The
study area has an elevation of 993 meters above sea level. Soils are mainly Estacado clay
loam, Lofton clay loam, Portales loam, Randall clay, and Zita loam with slopes from 0 to
1% (USDA, 1979). The climate is classified as semiarid with mild winters with average
annual temperature of 14 °C. The average minimum temperature in January is -3.8° C,
and the maximum in July averages 33.3°C. Most precipitation occurs from April to
October with an annual mean of 433 mm. The growing season is 208 days (National
Weather Service, 2005).
A 54 ha WW-B.Dahl pasture was used in this experiment. The pasture was
seeded in June of 1999 and used for grazing experiments since then. Prior to this
experiment two summers and one winter grazing trial were conducted, with a stocking
rate of approximately 2 head/hectare. For the present study before the grazing trial was
initiated, each year pasture was fertilized during the spring with ammonia sulfate at a rate
of 134.4 kg ha-1. The pasture was divided with electric fences into 12 paddocks, ranging
in size from 6.0 ha to 3.0 ha. To attain the objective in my study three levels of irrigation
97 and two treatments of energy supplement were established. Irrigation treatment consisted
in High Irrigation (HI), Low Irrigation (LI), and No Irrigation (NI) or dryland condition.
The amount of water applied to each treatment was: HI with 25.4 mm every 10 days, LI
with 25.4 mm every 20 days, and NI with zero water application. In addition the
supplement treatments consisted of supplement (S) (0.454 kg per head per day) and no
supplement (NS). Feed was offered three times a week around 1100 hours. The grazing
trial was conducted for two consecutive summers in 2003 and 2004. Each grazing trial was divided into three grazing periods. In 2003 the grazing trial was carried out in July,
August and September, with 32, 28, and 28 days for the first, second, and third grazing
period, respectively. In 2004 grazing trial was carried out in June, July, and August
having grazing periods of 28 days each. Experimental work was scheduled to begin in
June in both years, because difficulties acquiring the stocker in 2003 caused it to start one
month later. As a result field data were collected from July to early October in 2003 (88
days) and from June to August in 2004 (84 days).
During the study, cattle was handled under a protocol approved by the Texas Tech
University Animal Care and Use Committee. In both years, prior to the research initiated steers had two weeks of adaptation to the grazing area. Steers were vaccinated against respiratory and gastrointestinal diseases and treated for internal and external parasites.
An ear implant also was applied to steers at the beginning of the grazing trial. After the
adaptation period steers were randomly assigned to the experimental units (paddocks).
They were individually identified with ear tag and individually weighed at the beginning
of the grazing trial. Before the study began in both years, stocking rate for each paddock
98 was estimated based on standing crop, assuming 200 kg steer weight. It was also assumed 3% of forage intake based on body weight, and 70% of forage utilization.
During 2003 stocking rate for HI, LI, and NI was 2.3, 2.6, and 2.9 head per hectare, respectively. In 2004 stocking rate in HI, LI, and NI was 2.4, 1.9, and 1.8 head per hectare, respectively.
Data was gathered from individually weighed animals at the end of each grazing
period. Steers were weighed early in the morning after being held overnight without
access to feed and water. During the grazing trial steers had permanent access to fresh
and clean water and blocks of mixed minerals. Six water troughs were placed between
paddocks and six feeders were placed on paddock where supplement was offered (Figure
4.1).
Cattle performance was evaluated measuring daily weight gain and gain per
hectare. Average daily gain per steer and gain per hectare were analyzed as two factors completely randomized design with periods as repeated measures and paddocks as
experimental unit. Steers were considered as sampling units. Irrigation level was
considered as a main factor, supplement level as a sub-factor. Means separation was performed using the least significant difference (LSD) method. A 0.05 level of confidence was established to test significant differences.
99 Results and discussion
Average daily gain
Results from average daily gain in 2003 are shown in Figures 4.2, 4.3, and 4.4.
ADG was not affected by levels of irrigation and levels of supplement, but difference among periods was detected. Although, ADG differed in all periods, in August the highest ADG was observed while September was the lowest. Gain in August was approximately 32 and 73% higher than July and September.
During 2004 the effect of irrigation was similar to the previous year in which no differences in ADG were detected (Figure 4.5). In 2004 differences in ADG were detected between levels of supplement and among grazing periods (Figure 4.6 and Figure
4.7). Difference in ADG between levels of supplement were detected having S approximately 14% more gain than NS. Periods also had an effect in ADG; in June the highest ADG was detected and in August the lowest. Gain in June was approximately 38 and 31% higher than in July and August (Figure 4.7).
Gain per area
Results in average gain per area in 2003 showed a similar pattern from those observed for ADG in the same year. Irrigation and supplementation had no effect on gain per area (Figure 4.8 and Figure 4.9). Among periods gain per area in August was the highest and in September the lowest. Similar values were seen in July and August, showing on average approximately 64% more gain that September.
100 Results in average gain per area during 2004 are shown in Tables 4.11, 4.12, and
4.13. They are fairly similar to those observed in 2003. Neither level of irrigation nor
levels of supplement affected gain per area during 2004, but a difference was observed
among periods, in which June showed more gain per area exceeding to July and August with 39 and 31%. Similar values in gain per area were seen in July and August.
Large variations in water availability occurred during summer 2003 and 2004
when the study was conducted. During summer 2003 rainfall and water from irrigation accounted 192, 116, and 14.7 mm for HI, LI, and NI respectively. In summer 2004 rainfall was abundant compared with the previous summer. Total water availability in
summer 2004 (rainfall plus irrigation) was 396, 320, and 218 mm for HI, LI, and NI,
respectively. Because of the large difference in moisture conditions I was expecting
better steer performance in irrigated treatments mainly during summer 2003. Results
from my study however, suggested that level of irrigation had no effect in ADG and gain
per area in both years. Similar results were reported by Bezanilla (2002) in which water
availability and stocking rate were similar to my experiment. Furthermore, I expected
that higher levels of irrigation had higher forage quality values but it was not apparent in
my study. I theorized that the lack of effect of irrigation in steer performance was linked
to the lack of effect of irrigation detected in forage IVDMD and NDF in both years and
forage CP in the first year. According to my data, variation in these forage quality
indicators was negligible in 2003 and 2004.
Burns and Sollenberger (2002), Popp et al. (1997), and McCollum et al. (1998)
cited by Paisley et al. (2000) mentioned that sufficient forage availability and forage
101 quality are the cornerstones of satisfactory cattle performance. In my study in both years forage standing crop seemed to be adequate to meet demands. In contrast, forage crude protein levels were below minimum requirements for growing steers such as those used in my experiment. Forage TDN levels (considered as equal to forage IVDMD levels) were above minimal nutritional requirements (National Research Council (1984 and
1996) cited by Villalobos and Richardson, 1998).
Average daily gain and gain per area either under supplement or unsupplemented conditions in 2003 in all irrigation treatments showed similar patterns. Average daily gain and gain per area increased from the first to the second period and then decreased from the second to the third period. A similar pattern was observed in forage IVDMD.
In contrast, during 2004 regardless of level of supplement the pattern was in the opposite direction. Average daily gain and gain per area decreased from the first to the second period and then increased from the second to the third period. A similar pattern was detected in forage crude protein content. In vitro dry matter digestibility values were alike between periods in both years. According to these results there was not strong evidence that ADG and gain per hectare were affected by forage quantity or quality.
During 2003 and 2004 average daily gain and gain per area were not found in the same part of the grazing season. It is important to notice that grazing periods in these years did not begin in the same month. Coleman and Forbes (1998) reported better steer performance early in the growing season in Caucasian and Plains Old World bluestems when forage yield and quality were higher. Bezanilla (2002) also reported higher ADG at the beginning of the grazing trial in steers grazing WW-B.Dahl when more forage
102 standing crop peaked. In my study higher ADG and gain per area were observed at the
middle of the grazing trial in the first year and at the beginning of the grazing trial in the
second year. In both years higher steer performance did not correspond with higher
forage standing crop and quality. In addition, my results were not in agreement with
McCollum et al. (1998), and Ellis et al. (1984) cited by Paisley (2000) mentioning that
reduction in forage availability negatively affects cattle average daily gain and gain per
area because of reduction in forage intake and quality of the diet. My data suggested in
general that changes in forage standing crop were not in the same directions as changes in
forage quality.
The lack of relationship in the amount of forage yield, crude protein, IVDMD,
and NDF in my results let me theorize that positive steer performance observed in my study might be more related to morphological and physiological characteristics of WW-
B.Dahl grass. No measurement in leaf:stem ratio, leaf and stem size and weight, crude
protein and total non structured carbohydrate content in leaves were conducted in my
study. No measurements on effect of defoliation, plant response to graze and late
maturation under dry and moist conditions were conducted, but studies in WW-B.Dahl
and other Old World bluestems measuring these parameters (Buxton, 1996, Belesky and
Fedder , 1995; Dewald et al., 1995; McCollum, 2000; Sanderson et al., 1999; Svejcar and
Christiansen, 1987; Masters and Britton, 1988; and Philipp, 2004) support this
speculation.
Steer performance was satisfactory in 2003 and 2004 even when forage crude
protein results seemed low to ensure gain weight in the kind of steers used in my study.
103 Forage IVDMD results seem sufficient to the observed steer performance. Forage quality
from forage samples in average were 5.6 and 6.7% in CP content and 66 and 72% in
IVDMD in 2003 and 2004, respectively. Data from my experiment suggests that steers
were not able to gain weight because of lower content in forage crude protein. According
to information from the National Research Council (1984 and 1996) cited by Villalobos
and Richardson (1998), TDN intake in percentage, assuming being equal to IVDMD
percentage, surpassed NRC (1984 and 1986) recommendation for these steers in both
years.
Several factors not evaluated in this study may help to explain the satisfactory
steer performance below CP intake requirements. First, results of forage quality were
obtained from forage hand clippings. It is known that quality of diet in ruminants showed
difference in CP intake estimated from clippings and when it is measured from more sophisticated methodologies such as esophageal fistula. Second, I also assumed certain
degree of steer grazing selectivity which may increase crude protein intake as mentioned
by Buxton (1996).
As mentioned before CP content in forage was less than 7%. Many studies
recommended supplement cattle when crude protein in forage is below this percentage
(Sprinkle, 2000; Paterson et al., 1996; Villalobos and Britton 1992 and Pitts et al., 1988).
I was expecting that feeding a small amount of whole cottonseed would bring a positive
response in ADG and gain per hectare. Horn and McCollum (1987) recommended fed
energy supplement when forage nutrients content is below animal requirements to
maintain positive performance. Aiken (2002) suggested that energy supplementation in
104 growing cattle often enhances weigh gain. In my study the effect of whole cottonseed
supplement in ADG was not consistent and it was only observed during 2004. Perhaps the effect of supplement during this year was related to high forage IVDMD values. This result was not in agreement with Villalobos et al. (2000). They reported a 39% higher
ADG in steers supplemented with whole cottonseed against control while grazing a WW-
B.Dahl pasture in summer. They fed 40% more whole cottonseed per head.
Consequently, the amount of supplement offered to steers in my study suggested that it was not sufficient to enhance steer performance. In 2003 steers received 9.2 gram of supplement per kg of metabolic weight and in 2004 the amount was slightly low with 8 gram. Horn and McCollum (1987) recommended feeding energy supplement in amounts of approximately 30g/kg of metabolic weight without affecting cattle forage intake. It
seems from my results that large amounts of whole cottonseed may be fed to steers
grazing WW-B.Dahl pasture during the summer to boost beef gain.
Conclusions
Results from this study suggest that levels of irrigation had no effect on average
daily gain and gain per hectare of steer grazing WW-B.Dahl pasture. Variation in
moisture conditions prevailing during the conduct of my study seemed to maintain
sufficient forage standing crop and no changes in forage quality to affect steer
performance. Difference between periods in ADG and gain per hectare were detected in
2003 and 2004 but no consistent pattern of this effect was observed. Better steer
performance was not tied to peak forage standing crop and quality as was observed in
105 similar studies. Forage crude protein content during the length of study was below minimum nutritional requirements for growing cattle; nevertheless, positive cattle performance was achieved. Physiological and morphological characteristics of WW-
B.Dahl grass not measured during my study may influence satisfactory steer response.
The effect of feeding steers with small amounts of whole cottonseed was not reflected in
ADG and gain per area in both years. I assumed that the supplement effect was noticed when forage IVDMD values were higher. Results in steer performance from my study seemed to be linked to the complex animal forage interaction. In addition the digestible process of this grass in ruminants is not sufficient investigated. Therefore research should be conducted to gain a better understanding in the ruminal kinetic of WW-B.Dahl in stocker cattle to adequate grazing calendars and levels of supplemental feed. WW-
B.Dahl grass appears to enhance beef production during the growing season under different ranges of rainfall conditions in the Texas High Plains. Availability and cost of whole cottonseed in the region seems an attractive alternative as a supplement feed in growing cattle grazing this sort of pasture.
106
N County Road 6300 Farm Road 2716
Paddock 3 Paddock 4 Low Irrigation Low Irrigation Paddock 5 Supplement No Supplement High Irrigation Supplement
Paddock 2 Low Irrigation Supplement
Paddock 1 Low Irrigation No Supplement Paddock 6 High Irrigation Supplement
Paddock 12 No Irrigation Supplement Paddock 7 High Irrigation Paddock 11 No Supplement No Irrigation No Supplement Paddock 9 Paddock 10 No Irrigation No Irrigation No Supplement Paddock 8 Supplement High Irrigation No Supplement
Legend
Well Feeder Electric Fence
Water Trough Pens Irrigation System
Figure 4.1 Layout of grazing trial conducted in WW-B.Dahl pasture on Craig Farm in Lubbock County, Texas in summers 2003 and 2004.
107
1.0
a 0.8 a
) a -1
day 0.6 -1
0.4 ADG (kg head 0.2
0.0 High Irrigation Low Irrigation No Irrigation Level of Irrigation
Figure 4.2 Effect of level of irrigation on average daily gain (kg head-1 day-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture in summer 2003. Means with the same letter are not significant different (P > 0.05, LSD).
108
1.0
a 0.8 a ) -1
day 0.6 -1
0.4 ADG (kg head 0.2
0.0 No Supplement Supplement Supplement Level
Figure 4.3 Effect of level of supplementation (whole cottonseed at 0.0 and 0.454 kg head-1 day-1) on average daily gain (kg head-1 day-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2003. Means with the same letter are not significant different (P > 0.05, LSD).
109
1.2
1.0 a ) -1 0.8 b day -1 0.6 c
0.4 ADG (kg head 0.2
0.0 July August September Period
Figure 4.4 Effect of grazing period on average daily gain (kg head-1 day-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2003. Means with different letter are significant different (P < 0.05, LSD).
110
1.2
aa 1.0 a ) -1 0.8 day -1 0.6
0.4 ADG (kg head
0.2
0.0 High Irrigation Low Irrigation No Irrigation Irrigation level
Figure 4.5 Effect of level of irrigation on average daily gain (kg head-1 day-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture in summer 2004. Means with the same letter are not significant different (P > 0.05, LSD).
111
1.2 a 1.0 b ) -1 0.8 day -1 0.6
0.4 ADG (kg head
0.2
0.0 No Supplement Supplement Supplement Level
Figure 4.6 Effect of level of supplementation (whole cottonseed at 0.0 and 0.454 kg head-1 day-1) on average daily gain (kg head-1 day-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004. Means with the same letter are not significant different (P > 0.05, LSD).
112
1.4
1.2 a
) 1.0 -1 b b day
-1 0.8
0.6
ADG (kg head 0.4
0.2
0.0 June July August Period
Figure 4.7 Effect of grazing period on average daily gain (kg head-1 day-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004. Means with different letter are significant different (P < 0.05, LSD).
113
65 a a 60 ) -1 55 a 50
45
40 Average Gain per (kg ha Area 35
30 High Irriagtion Low Irrigation No Irrigation Irrigation Level
Figure 4.8 Effect of level of irrigation on average gain per area (kg ha-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture in summer 2003. Means with the same letter are not significant different (P > 0.05, LSD).
114
65
a )
-1 60
a 55
50
45 Average Gain per Area (kg ha (kg Area per Gain Average
40 No Supplement Supplement Supplement Level
Figure 4.9 Effect of level of supplementation (whole cottonseed at 0.0 and 0.454 kg head-1 day-1) on average gain per area (kg ha-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2003. Means with the same letter are not significant different (P > 0.05, LSD).
115
80 a 70 )
-1 a 60
50 b 40
30
20 Average Gain per Area (kg ha (kg Area per Gain Average 10
0 July August September Period
Figure 4.10 Effect of grazing period on average gain per area (kg ha-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2003. Means with different letter are significant different (P < 0.05, LSD).
116
70 a 60 ) a -1 a 50
40
30
20 Average Gain per Area (kg ha (kg Area per Gain Average 10
0 High Irrigation Low Irrigation No Irrigation Irrigation Level
Figure 4.11 Effect of level of irrigation on average gain per area (kg ha-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004. Means with the same letter are not significant different (P > 0.05, LSD).
117
65 )
-1 60 a
a 55
50
45 Average Gain per Area (kg ha
40 No Supplement Supplement Supplement Level
Figure 4.12 Effect of level of supplementation (whole cottonseed at 0.0 and 0.454 kg head-1 day-1) on average gain per area (kg ha-1) on steers grazing in WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004. Means with different letter are significant different (P > 0.05, LSD).
118
80
70 a ) -1 60 b b 50
40
30
20 Average Gain per Area (kg ha (kg Area per Gain Average 10
0 June July August Period
Figure 4.13 Effect of grazing period on average gain per area (kg ha-1) on steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation in summer 2004. Means with different letter are significant different (P < 0.05, LSD).
119 References
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Allen, V.G., C.P. Brown, R. Kellison, E. Segarra, T. Wheeler, P.A. Dotray, J.C.Conkwright, C.J. Green, and V. Acosta-Martinez.2005. Integrating cotton and beef production to reduce water withdrawal from the Ogallala aquifer in the Southern High Plains. Agron. J. 97:556-567.
Belesky, D.P. and J.M. Fedders. 1995. Warm-season grass productivity and growth rate as influenced by canopy management. Agron. J. 87:42-48.
Bezanilla, A.G. 2002. Effect of irrigation and grazing systems on steer performance and plant response in an Old World bluestem pasture. Texas Tech University. Master Thesis. 56 p.
Burns, J.C. and L.E. Sollenberger. 2002. Grazing behavior of ruminants and daily performance from warm-season grasses. Crop Sci. 42:873-881.
Buxton, D. R. 1996. Quality-related characteristics of forage as influenced by plant environment and agronomic factors. Animal Feed Science Technology. 59:37-49.
Coleman, S.W. and T.D.A. Forbes. 1998. Herbage characteristics and performance of steers grazing Old World bluestem. J. Range Manage. 51:399-407.
Dewald, C. L., P.L. Sims, and Berg, W. A. 1995. Registration of ‘WW-B.Dahl’ old world bluestem. Crop Sci. 35:937.
Gillen, R.L. and W.A. Berg. 2001. Complementary grazing of native pasture and old world bluestem. J. Range Manage. 54:348-355.
Hodges, M. and T.G. Bidwell. 1993. Production and management of old world bluestems. Oklahoma Cooperative Extension Service. Division of Agricultural Sciences and Natural Resources F 3020.
Horn, G.W. and F. T. McCollum. 1987. Energy supplementation of grazing ruminants. Proceedings, Grazing Livestock Nutrition Conference. Pages 125-136
Kloppenburg, P.B., H.E. Kiesling, R.E. Kirksey, and G.B. Donart. 1995. Forage quality, intake, and digestibility of year long pastures for steers. J. of Range Manage. 48:542-548.
120 Masters, R.A. and C.M. Britton. 1988. Response of WW-517 old world bluestem to fertilization, watering, and clipping. Texas Journal of Agriculture and Natural Resources. 2:48-53.
McCollum, T. 2000. Old world bluestem pasture management strategies. Plains Nutritional Council Fall Grazing Conference. Texas A&M University. Agricultural Research and Extension Center, Amarillo, TX. Publication No. AREC 00-45. pp 11-17.
National Weather Service. 2005. http:// www.srh.noaa.gov/lub/climat. [Accessed Friday March 18].
Paisley, S.I. 2000. Supplements for stockers grazing winter cereal forage. Management strategies for cattle on range and pasture. Texas A & M University Agricultural Research and Extension Center Amarillo. Publication No. AREC 00-45.
Paterson, J., R.Cochran, and T. Klopfenstein. 1996. Degradable and undegradable protein responses of cattle consuming forage-based diets. Proceedings Grazing Livestock Nutrition Conference. Pages 94-103.
Philipp, D., 2004. Water use efficiency and nutritive value of three old world bluestems.(Bothriochloa spp) Disseratation. Texas Tech University. Lubbock, TX. 195 p.
Pitts, J.S., T. McCollum, and C.M. Britton. 1988. Effect of protein supplementation on weight gain of steers grazing tobosagrass range. p. 23. In Research highlights. Dep. Range Wildlife Mgt., Texas Tech University., Lubbock.
Popp, J.D., W.P. McCaughey, and R.D.H. Cohen. 1997. Effect of grazing system, stocking rate and season of use on herbage intake and grazing behavior of stocker cattle grazing alfalfa-grass pasture. Can. J. Anim. Sci. 77:677-682.
Sanderson, M. A., P. W. Voigt, and R. M. Jones. 1999. Yield, and quality of warm- season grasses in central Texas. J. of Range Manage 52:145-150.
Sprinkle, J., 2000. Protein supplementation. The University of Arizona, Cooperative Extension. 11/00 AZ 1186.
Svejcar, T. and S. Christiansen. 1987. Grazing effect on water relationship of Caucasian bluestem. Journal of Range Management. 40 (1) 15-18.
United States Department of Agriculture.1979. Soil Survey of Lubbock County Texas.. Soil Conservation Service in cooperation with Texas Agricultural Experimental Station.
121
Villalobos, C. and C.M. Britton,. 1992. Protein supplementation in stockers on tobosagrass rangeland. p. 9-11. In Research highlights. Dep. Range Wildlife Mgt., Texas Tech University., Lubbock.
Villalobos, C. and C.R. Richardson. 1998. Nutritional value of range plants on the Texas regions. The Center for Feed Industry Research and Education. Department of Animal Science and Food Technology. Texas Tech University, Lubbock, TX CFIRE Annual Report 98-103-t5-382.
Villalobos, C., M. Avila, G. Bezanilla, and C.M. Britton. 2000. Supplementation effects on steer performance grazing old world bluestem. p. 24. In Research highlights. Dep. Range,Wildlife, & Fisheries Mgt., Texas Tech University., Lubbock.
Villalobos, C., M. Avila, G. Bezanilla, and C.M. Britton. 2002. Cattle performance grazing WW-B.Dahl Old World bluestem with different sources of protein supplementation. p. 23-24. In Research highlights. Dep. Range,Wildlife, & Fisheries Mgt., Texas Tech University., Lubbock.
Wang, Y.W., S. Simecek, and M. A. Hussey.1992. Forage production for selected old world bluestems at College Station, 1990-92.
White, L. M. and CH. L. Dewald. 1996. Yield and quality of WW-Iron Master and caucasinan bluestem regrowth. J. Range Manage. 49:42-45.
122 CHAPTER V
EFFECT OF LEVEL OF IRRIGATION AND WHOLE COTTONSEED SUPPLEMENT
ON FORAGE UTILIZATION BY STEERS GRAZING A WW-B.DAHL (Bothriochloa
bladhii) PASTURE DURING SUMMER.
Abstract
Evaluation of forage utilization in a WW-B.Dahl [Bothriochloa bladhii (Retz)
S.T. Blake] pasture using the paired plot with movable cages was performed in Lubbock
County, Texas. The effect of levels of irrigation, grazing periods and supplement were evaluated on forage utilization. Three levels of irrigation and two supplement treatments were established. Irrigation treatments were: High Irrigation (HI) (25.4 mm every 10 days); Low Irrigation (LI) (25.4 mm every 20 days) and; No Irrigation (NI). Supplement treatments were (S) (0.454 kg of whole cottonseed/head/day) fed three times a week and no supplement (NS). The grazing trial was divided into three equal periods starting in
July 2003 and June 2004. The experimental animals used in this study were 142 steers with initial average weight of 181.0 kg (SD ± 30.7 kg) in 2003 and 108 steers with initial average weight of 214.9 kg (SD ± 26.2 kg) in 2004. Results showed that levels of irrigation and supplement feed had no effect (P > 0.05) in forage utilization in both years.
Among periods differences (P < 0.05) were observed in 2003 and 2004. In general, results in forage utilization in WW-B.Dahl pasture followed similar trends either among levels of irrigation or among periods in both years. Periods were different showing the lowest forage utilization values at the beginning of the study and the highest at the end.
123 Forage utilization was similar between supplement treatments. Variation in forage
utilization appeared not related to changes in forage standing crop and quality. Is likely
that regrowth pattern in WW-B.Dahl grass during the growing season may eliminate any
expected tendency in forage utilization. Results suggested that the paired plot method
with movable cages may not be adequate to measure forage utilization in WW-B.Dahl
pasture. Subjectivity in the procedure and morphology of the grass may result in
overestimating forage utilization.
Introduction
Forage utilization has been measured since domestication of herbivores. In the
early times judgments were ocular and subject to experience of evaluators. The U.S.
Forest Service was the first agency to formally attempt to control forage utilization
(Heady, 1949). Since then, misunderstanding and controversy have been prevalent in
measurement and interpretation of forage utilization. Early definition on forage
utilization was stated by the Society of American Foresters in 1944 (Heady, 1949) more
recently, the Forage and Grazing Terminology Committee in 1989 defined forage
utilization as “the degree to which animals have removed the current growth of herbage”
(SRM, 1992).
Estimation of forage utilization is crucial in range or pasture management (Hyder
et al., 2003). Assessment in forage utilization may be categorized in estimation methods
and measurement methods. These methods have been generating controversy in regard
to their applicability, accuracy, and result interpretation. Several studies comparing these
124 methods have ended up in construction of conceptual models and incorporation of new
technology.
Clearly, measurement in forage utilization provides ranchers and range managers information to support decisions in adjusting stocking rate and grazing distribution.
Nevertheless, information regarding forage utilization is poor and still generating controversy. The objective of this study was to estimate the percentage of forage utilization by steers grazing a WW-B.Dahl pasture in summer under different levels of irrigation and supplementation.
Material and Methods
The study was conducted for two consecutive summers, 2003 and 2004, in an Old
World bluestem improved pasture located at the Craig Farm in Lubbock County, Texas.
The study area has an elevation of 993 meters above sea level. Soils are mainly Estacado
clay loam, Lofton clay loam, Portales loam, Randall clay, and Zita loam with slopes from
0 to 1% (USDA, 1979). The climate is classified as semiarid with mild winters with
average annual temperature of 14 °C. The average minimum temperature in January is -
3.8° C, and the maximum in July averages 33.3°C. Most precipitation occurs from April
to October with an annual mean of 433 mm. The growing season is 208 days (National
Weather Service, 2005).
A 54 ha WW-B.Dahl pasture was used in this experiment. The pasture was
seeded in June of 1999 and used for grazing experiments since then. Previous to the
experiment pasture was fertilized each spring with ammonium sulfate at a rate of 134.4
125 kg ha-1. The pasture was divided with electric fences into 12 paddocks ranging in size
from 6.0 ha to 3.0 ha. To accomplish my objective three levels of irrigation and two
supplementation treatments were established between paddocks in which steers were
grazing. Levels of irrigation consisted in High Irrigation (HI), Low Irrigation (LI), and
No Irrigation (NI) or dryland condition. The amount of water applied to each treatment
was: HI with 25.4 mm every 10 days, LI with 25.4 mm every 20 days, and NI with zero
water application. In addition supplement treatments consisted in supplement (S)
(feeding 0.454 kg per head per day of whole cottonseed) and no supplement (NS). Feed
was offered three times a week around 1100 hours. During each summer irrigation trial
was divided into three periods: 32, 28, and 28 days in 2003, and three equal periods of 28
days in 2004. Field data were collected from July to early October in 2003 (88 days) and
from June to August in 2004 (84 days). In the experiment were used 142 steers with
initial average weight of 181.0 kg (SD ± 30.7 kg) in 2003 and 108 steers with initial
average weight of 214.9 kg (SD ± 26.2 kg) in 2004.
The paired plot method with movable cages was used to estimate the effect of levels of irrigation, steer grazing, and supplementation on forage utilization (SRM, 1986).
The method was implemented at the beginning of the grazing trial. First, two plots were
randomly selected using a 0.25 m2 quadrat, and then a coin was tossed to determine
which plot would be caged. Second, an adjacent plot with similar characteristics to the previously caged was selected and clipped. Forage clipped from this plot was used to estimate forage standing crop at the beginning of the grazing trial. This clipped sample also was used to estimate forage regrowth for the following grazing period. Third, at the
126 middle of each grazing period forage clippings were carried out to obtain samples from
inside and outside cages. This procedure was repeated during the following three grazing periods. The percentage of forage utilization was calculated by the following formula.
PFU = {((FWIC – FWOC) ÷ FWIC) x 100}
where
PFU = percentage of forage utilization.
FWIC = forage weight inside cage
FWOC = forage weight of outside cage
For my study 60 movable cages were built with 10 x 10 cm mesh galvanized wire.
Each cage had one square meter of base having enough space to hold the quadrat used for forage clippings. To keep cages attached to the ground a couple of 1.5 meter metallic rods were used as anchors, avoiding cage folding or twisting by steers. Five cages per paddock were used with a total of 20 cages per irrigation treatment. Forty samples per irrigation/period were obtained (20 inside and 20 outside).
Data collected from forage utilization samples were analyzed in factorial
completely randomized design with periods as repeated measurements. Levels of
irrigation and supplement treatments were treated as factor and sub-factor respectively.
Forage clippings from inside and outside of cages were considered sample units.
127 Results and discussion
Results from PFU during 2003 are shown in Table 5.1. No effect of levels of irrigation and supplementation in PFU was noted. Differences were observed among grazing periods. In addition a three way interaction among irrigation - supplement - period was observed. Due to the three way interaction, means were analyzed across HI treatment. When PFU means were analyzed within irrigation and supplement, August and September differed from July at NS treatment. Similar values in PFU were observed in August and September, being more than two times higher than value detected in July.
Additionally, when PFU means were analyzed within irrigation and period, difference between supplement treatments was seen only in September. No supplement treatment had higher PFU value than S, having approximately two times more forage utilization than S. Finally, when PFU means were analyzed within period and NS treatment, irrigation differed only in August. During August LI showed the highest PFU value and
NI the lowest. In the same period HI observed similar PFU value than LI and NI.
Results from year 2004 were similar to those observed in 2003 in which irrigation and supplement had no effect in PFU. During this year no interaction was seen.
Differences among periods similar to first year were observed (Table 5.2), recording the highest value in August and the lowest in June and July. In August PFU was approximately 34% higher than in June and July.
Large variation in water availability occurred between summer 2003 and 2004 when my study was conducted. During summer 2003 rainfall and water from irrigation accounted 192, 116, and 14.7 mm for HI, LI, and NI, respectively. In summer 2004
128 rainfall was abundant compared to the previous summer. Total water availability in summer 2004 (rainfall plus irrigation) was 396, 320, and 218 mm for HI, LI, and NI respectively. Even though disparities between water availability were evident in those years, PFU showed similar patterns among levels of irrigation. Low irrigation treatment showed the higher PFU value and HI the lowest. Percentage of forage utilization in LI surpassed NI and HI by 7 and 18% respectively in 2003. During 2004 LI surpassed NI and HI by 19 and 25% respectively.
Parallel to this study, data were collected in forage standing crop, forage quality, and steer performance. I was expecting that results from forage utilization and forage standing crop among levels of irrigation followed opposite trend due to the effect of irrigation and grazing pressure. This relationship was not found to determine this relationship did not hold, data from forage utilization and steer weight collected during my study were used to estimate forage regrowth and forage intake. Estimations in forage regrowth expressed in kg per ha (using the formula described by Scrivner et al., 1986) and steer forage intake (based on 3% body weight) were conducted per each level of irrigation in both years. These estimations were contrasted to determine the lack of relationship among forage standing crop and forage utilization. Then estimated forage regrowth exceeded estimated forage intake in 2003 and 2004. Comparison between forage utilization and forage regrowth showed that regrowth exceeded utilization in HI in
2003 and all levels of irrigation in 2004 (Table 5.3). Overall results suggested that forage regrowth between levels of irrigation was sufficient to cover the forage demand in 2003 and 2004 and may explain the lack of relationship initially expected.
129 Regarding grazing periods, PFU showed similar trend in both years. Regardless
of the levels of irrigation, PFU increased as grazing trial progressed. I hypothesized that
forage standing crop would be decreasing as growing season advance. As a result forage
reduction in forage standing crop would be reflected in higher forage utilization. This
relationship was evident during the first year of study and in NI treatment in 2004. It was
not apparent in HI and LI during the second year. Similar estimations as conducted
between levels of irrigation were performed among periods in both years. Results
showed that forage regrowth exceeded forage intake in all periods in 2003 and 2004
(Table 5.4). Differences were more evident in the first period than in the last two periods
in both years. In addition estimation in forage regrowth was compared against forage
utilization values in the same manner in which it was done between levels of irrigation.
Results from these comparisons showed that forage regrowth was high in July and low in
August and September in 2003. Estimated regrowth in July was two times higher than
forage utilization. I believe that the exceeding forage regrowth in this period was enough
to compensate for the shortage in following periods. During 2004 forage regrowth was
high in June and August and low in July. The lack of forage regrowth to equal or surpass
forage utilization in July may have been compensated for with previous period regrowth.
Losses in forage regrowth in later periods seemed to be compensating for higher forage
regrowth in the earlier period. These results suggested that forage availability among periods was higher than steer forage demand in both years.
Observed forage utilization results among levels of irrigation and among period in
2003 and 2004 may have been influenced by forage regrowth. This evidence indicates
130 that WW-B.Dahl grass may have the ability to initiate regrowth under varied moisture
conditions and throughout the growing season. Forage standing crop at the beginning of
the grazing trial plus forage regrowth throughout the grazing periods were able to
maintain sufficient forage availability and fulfill the forage intake requirements for
growing cattle. No pattern between PFU and forage standing crop was encountered. The
70% forage utilization initially proposed was not accomplished. In addition, forage
quality measurements in terms of crude protein and in vitro dry matter digestibility
showed small variation in both years. It is likely that low variation in forage crude
protein and in vitro dry matter digestibility showing during the two years of evaluation
had no effect on forage utilization.
Level of supplement had no effect on PFU during the two years of study, under no
supplement conditions PFU values were approximately 12% higher than supplement in
both years. I presumed that steers fed with energy supplement might have increased
forage utilization as mentioned by Bowman and Sanson (1996) for high fiber energy
supplements, but in my study it did not happen. Steers consuming whole cottonseed received 9.2 and 8.0 g/kg of metabolic weight in 2003 and 2004 respectively at the
beginning of the grazing period. This amount was 3.4 times lower than the maximum
limit recommended to avoid negative affect in forage intake (Horn and McCollum, 1987).
Therefore the amount of supplement offered (0.454 kg/head/day) and the source of energy present in whole cottonseed (Luginbuhl et al., 2000; Harvatine et al., 2002) appeared not to influence forage intake in the steers used in this study. PFU was also not
131 affected. Results suggested that the small amount of supplement offered to steers in this study was not sufficient to affect forage utilization.
To identify under or overestimation in PFU values observed in my study, estimations in steer forage intake previously conducted were compared against forage utilization values (Table 5.3 and Table 5.4). Results suggested that forage utilization was overestimated in both years in all my treatments. During 2003 forage utilization was 30,
46, and 22% higher than estimated forage intake for HI, LI and NI respectively. Similar differences were detected in 2004 in which forage utilization was 33, 50, and 28% higher than estimated forage intake for HI, LI, and NI respectively. Analogous comparisons were performed between grazing periods. Results during 2003 showed that forage utilization was 28, 72, and 61% higher than estimated forage intake in July, August, and
September. In the second year also, forage utilization showed high values in regard to estimated forage intake. In June, July, and August forage utilization surpassed estimated forage intake by 60, 33, and 113% respectively. These results suggested that the paired plot method used in my study seems to be unsuitable to evaluate forage utilization in
WW-B.Dahl pastures grazed during summer.
Conclusions
Results from this study showed that levels of irrigation had no effect on forage utilization. I was expecting higher forage utilization in treatments in which forage yield was low due to moisture conditions. Higher forage utilization was expected because of increasing forage demand by growing steer used in the experiment. It was not evident in
132 my study. Estimations in forage regrowth and forage intake permitted elucidate the lack of this relationship. Results from these estimations let me hypothesize that regrowth in
WW-B.Dahl grass provided sufficient forage to meet steer demand regardless level of
irrigation. Similar conclusions may apply in forage utilization among periods. In regard
to supplement, feeding whole cottonseed to steers had no effect in forage utilization. The
amount of supplement fed during my study appeared to be limited to expect different
results.
Measurements on forage utilization with the paired plot method with movable
cages appeared unsuitable in WW-B.Dahl pasture. It was suggested by the overestimated
result when compared with estimations in steer forage intake and actual values in forage
utilization. The method is subject to personal judgments in its application. Another
factor that likely encourages overestimation in forage utilization in this study may be
related with canopy structure of WW-B.Dahl grass. This structure seems to make it
difficult to mimic cattle grazing by hand clippings. As a result, accumulation of errors
may result in overestimation on forage utilization (McNaughton et al., 1996). Forage
utilization and its interpretation should be defined for particular situations in which it is
estimated (Frost et al., 1994). Further, methodology should be straightforward, accurate,
easy to understand amd interpret, and not be time consuming in its application (Roach,
1950; Schmutz et al., 1963; Hyder et al., 2003). The use of digital photography may
render better results in measuring forage utilization in WW-B.Dahl pastures.
133
Table 5.1 Effect of levels of irrigation and supplement (S) and no supplement (NS) on forage utilization by steers grazing in WW-B Dahl (Bothriochloa bladhii) pasture in summer 2003.
Period
Treatment Supplement July August September Mean
------%------
NS 19.71b1A2x3 40.36aAxy 46.36aAx 35.57
High Irrigation S 25.69aA 26.95aA 24.54aB 25.73
Mean 22.70 33.65 35.59 30.65
NS 38.58x 42.59x 53.08x 44.75
Low Irrigation S 15.61 24.68 43.05 27.78
Mean 27.10 33.64 48.07 36.27
NS 24.96x 20.41y 31.72x 25.70
No Irrigation S 19.19 54.24 51.70 41.70
Mean 22.07 37.33 41.71 33.70
Mean 23.96B 34.87A 41.79A 33.54
1 Period means within a treatment and supplement followed by the same lower case letter (a,b,c) are not significant different (P > 0.05 LSD). 2 Supplement within irrigation and period followed by the same upper case letter (A, B, C) are not significant different (P > 0.05 LSD). 3Treatment within a period and supplement followed by the same lower case letter (x,y,and z) are not significant different (P > 0.05 LSD).
134
Table 5.2 Effect of level of irrigation and supplement (S) and no supplement (NS) on forage utilization by steers grazing in WW-B Dahl (Bothriochloa bladhii) pasture in summer 2004.
Period
Treatment Supplement June July August Mean
------%------
NS 46.30 36.41 54.74 45.81
High Irrigation S 28.90 25.28 44.40 32.86
Mean 37.60 30.84 49.57 39.34a1
NS 53.34 42.27 64.70 53.44
Low Irrigation S 41.70 52.01 42.49 45.40
Mean 47.52 47.14 53.60 49.42a
NS 12.22 39.54 68.26 39.01
No Irrigation S 39.64 30.31 61.25 43.73
Mean 25.93 33.42 64.75 41.37a
Mean 37.02B2 37.13B 55.97A 43.37
1 Treatment means followed by the same lower case letter are not significant different (P > 0.05 LSD). 2 Period means followed by the same upper case letter are not significant different (P > 0.05 LSD).
135
Table 5.3 Measurement in forage utilization and estimation in forage regrowth and forage intake of steers grazing a WW-B.Dahl (Bothriochloa bladhii) pasture under three levels of irrigation high irrigation (HI), low irrigation (LI), and no irrigation (NI) in summer 2003 and 2004.
Treatment
HI LI NI HI LI NI
Item 2003 2004
------kg ha-1------Forage utilization1 802 956 744 857 939 631
Forage regrowth2 1,052 879 699 1,011 1,119 749
Forage intake3 485 512 576 557 442 426
1Forage utilization was derived from the difference between forage inside and outside cages. 2Forage growth estimation derived from the Scrivner et al. (1986) formula. 3Forage intake is an estimation derived from the steers live weight per ha and assuming forage intake based on 3% body weight.
136
Table 5. 4 Measurements in forage utilization and estimation in forage regrowth and forage intake of steers grazing in a WW-B.Dahl (Bothriochloa bladhii) pasture subject to three levels of irrigation during three grazing periods in summer 2003 and 2004.
Period
July August Sept June July August
Item 2003 2004
------kg ha-1------Forage utilization1 663 880 959 695 630 1,101
Forage regrowth2 1,379 605 646 950 571 1,358
Forage intake3 517 511 595 433 474 517
1Forage utilization was derived from the difference between forage inside and outside cages. 2Forage growth is estimation derived from the Scrivner et al. (1986) formula. 3Forage intake is an estimation derived from the steers live weight per ha and assuming forage intake based on 3% body weight.
137 References
Bowman, J.G.P., and D. W. Sanson. 1996. Starch- or fiber-based energy supplements for grazing ruminants. Proceeding, Grazing Livestock Nutrition Conference. July 18-19. Pages 118-135.
Frost, W.E., E.L. Smith, and P.R. Ogden. 1994. Utilization guidelines. Rangelands. 16:256-259.
Harvatine, D.I., J.E. Winkler, M. Devant-Guille, J.L. Firkins, N.R. St-Pierre, B.S. Oldick, and M.L. Eastridge. 2002. Whole linted cottonseed as a forage substitute: Fiber effectiveness and digestion kinetics. J. Dairy Sci. 85:1988-1999.
Heady, H.F. 1949. Methods of determining utilization of range forage. J. of Range Manage. 2:53-63.
Horn, G.W. and F. T. McCollum. 1987. Energy Supplementation of Grazing Ruminants. Proceedings, Grazing Livestock Nutrition Conference. Pages 125-136
Hyder, P.W., E.L. Fredrickson, M.D. Remmenga, E.E. Estell, R.D. Pieper, and D.M. Anderson. 2003. A digital photographic technique for assessing forage utilization. J. Range Manage. 56:140-145.
Luginbuhl, M.H. Poore, and A.P. Conrad. 2000. Effect of level of whole cottonseed on intake, digestibility, and performance of growing male goats fed hay-based diets. J. Anim. Sci. 78:1677-1683.
McNaughton, S.J., D.G. Milchunas, and D.A. Frank. 1996. How can net primary productivity be measured in grazing ecosystems? Ecology 77:974-977.
National Weather Service. 2005. http:// www.srh.noaa.gov/lub/climat. [Accessed Friday March 18].
Roach, M. E. 1950. Estimating perennial grass utilization on semidesert cattle ranges by percentage of ungrazed plants. J. of Range Manage. 3:182-185.
Schmutz, E.M., G.A. Holt, and C. C. Michaels. 1963. Grazed-class method of estimating forage utilization. J. Range Manage. 16:54-69.
Scrivner, J.H., D. Michael Center, and M.B. Jones. 1986. A rising plate meter for estimating production and utilization. J. of Range Manage. 39:475-477.
The Society of Range Management. 1992.Terminology for grazing lands and grazing animals. Forage and Grazing Terminology Committee. J. Prod. Agric. 5:191-201.
138
The Society of Range Management. 1986. Methods of measuring herbage and browse utilization. Range Research: Basic problems and techniques. Edited by C.Wayne Cook and James Stubbendieck. Chapter 5. pages 120-132.
United States Department of Agriculture.1979. Soil Survey of Lubbock County Texas.. Soil Conservation Service in cooperation with Texas Agricultural Experimental Station.
139 CHAPTER VI
ECONOMIC ANALYSIS OF BEEF PRODUCTION IN WW B. DAHL (Bothriochloa bladhii) PASTURE UNDER DIFFERENT COMBINATIONS OF IRRIGATION AND
SUPPLEMENT.
Abstract
Economic analysis was performed on beef production in WW-B.Dahl
[Bothriochloa bladhii (Retz) S.T. Blake] pasture under six combinations of irrigation and supplement in Lubbock, County Texas. For two consecutive summers a 54 ha WW-
B.Dahl pasture held LI-S (low irrigation-supplement), LI-NS (low irrigation-no supplement), HI-S (high irrigation-supplement), HI-NS (high irrigation-no supplement),
NI-S (no irrigation-supplement), and NI-NS (no irrigation-no supplement) production scenarios. Production scenarios under irrigated conditions received 192 and 116 mm of water in 2003 and 396 and 320 mm during 2004 for HI and LI, respectively. Production scenarios under dryland conditions received 14.7 and 218 mm of water in 2003 and 2004, respectively. The grazing trials were 88 days in 2003 with 142 steers (181.0 kg initial bodyweight) and 84 days in 2004 with 108 steers (214.9 kg initial bodyweight) in 2004.
Steers under supplementation were fed with whole cottonseed three times a week at 0.454 kg/head/day. For each production scenario beef production cost in dollars per kilogram and dollars per ha were estimated. Profit was defined as returns to land, management, and irrigation water were estimated in dollar per hectare for each production scenario.
Expenditures for electricity, fertilizer, irrigation equipment maintenance, labor, feed,
140 interest in steer investment, veterinary supplies, and minerals were considered in the
analysis. Steer buying and selling price was considered according to the beginning and
ending of the grazing trial. Steer prices were taken from the average US weekly steer
report for the Texas Panhandle region. Results showed that the NI-NS scenario in 2003
and the NI-S scenario in 2004 were the most profitable production activities with a retrun
of $305.95 and $222.89/ha, respectively. Beef production cost in dollars per kg was
lower in the NI-NS scenario in both years. Cost of electricity, fertilizer, and of irrigation
system maintenance accounted for the highest percentage of the total operating costs in
both years. In dry years the profit difference between irrigated and dryland scenarios was
greater than in wet years. Feeding a small amount of whole cottonseed was not cost
effective. Steer market conditions also have influence the profitability of the enterprise.
In general, incorporation of WW-B.Dahl into the forage/beef production systems of the
Texas High Plains is profitable under dryland conditions. Moreover it may encourage the transition from traditional crops to perennial forage, thereby adding stability to the agricultural economy in the region.
Introduction
In the Texas High Plains agriculture heavily depends on underground water from
the Ogallala aquifer. The continuing depletion of the aquifer is shifting land use from
irrigated cropping systems to dryland systems. This change will affect farmers and the
regional economy (Johnson et al., 2004). Past research has focused on agricultural
practices that will extend the economic life of the aquifer and protect the regional
141 economy. Proposed solutions have raised from planting crops that demand less water
(Terrell and Johnson, 1999; Johnson et al., 2004) to implementing new forage/beef
production systems (Philipp, 2004; Allen et al., 2005).
Linear programming models have been used to analyze stocker enterprises in Old
World bluestem pastures in the Texas High Plains (Ethridge et al., 1987; Ethridge et al.,
1990; Almas, 1999). Computer software has been developed to economically evaluate
livestock enterprises such as stocker production system in improved pastures (Williams et
al., 1988; Kreuter et al., 1996). Economic analysis of net return per head and per area in
Old World bluestem pasture under different stocking rates was performed by Phillips and
Coleman (1995). Brorsen et al. (1983) developed a model to estimate growth pattern and
economic outcomes in stocker operations. Bransby (1989) analyzed the profitability of
bermudagrasses pasture subjected to variable stocking rates with stockers. However, no information is available for evaluating the profitability of producing beef in WW-B.Dahl pastures under diverse irrigation conditions in the Texas High Plains. The objective of this study was to perform an economic analysis of a stocker operation in a WW-B.Dahl pasture during summer.
Material and Methods
This economic analysis was conducted for two consecutive summers, 2003 and
2004, in an Old World bluestem WW-B.Dahl pasture located at the Craig Farm in
Lubbock County, Texas. The study area has an elevation of 993 meters above sea level.
Soils are mainly Estacado clay loam, Lofton clay loam, Portales loam, Randall clay, and
142 Zita loam with slopes from 0 to 1% (USDA, 1979). The climate is classified as semiarid
with mild winters with average annual temperature of 14 °C. The average minimum
temperature in January is -3.8° C, and the average maximum temperature in July is
33.3°C. Most precipitation occurs from April to October with an annual mean of 433
mm. The growing season is 208 days (National Weather Service, 2005). A 54 ha WW-
B.Dahl pasture was used in this experiment. The pasture was seeded in June of 1999 and
used for grazing experiments since then. Previous to the experiment, pasture was
fertilized each spring with ammonia sulfate at a rate of 134.4 kg ha-1.
The six beef production scenarios were developed for alternative combinations of
irrigation and feed supplement levels. These six combinations were: High irrigation-
Supplement (HI-S), High irrigation-No supplement (HI-NS), Low irrigation-Supplement
(LI-S), Low irrigation-No supplement (LI-NS), No irrigation-Supplement (NI-S), and No
irrigation-No supplement (NI-NS). The size of the beef production scenarios ranges from
8.37 to 9.43 hectares. Irrigation levels consisted of High Irrigation (HI), Low Irrigation
(LI), and No Irrigation (NI) or dryland condition. The amount of water applied to each
treatment was: HI with 25.4 mm every 10 days, LI with 25.4 mm every 20 days, and NI
with zero water application. The supplement treatments consisted of supplement (S)
(0.454 kg per head per day of whole cottonseed fed three times a week) and no
supplement (NS). Experimental animals used for the grazing trial during this study were
142 steers with an average initial weight of 181.0 kg (SD ± 30.7 kg) in 2003 and 108
steers with an average initial weight 214.9 kg (SD ± 26.2 kg) in 2004. The grazing trial
duration was 88 and 84 days for summer 2003 and 2004, respectively. On average,
143 stocking rate was 478 and 448 kg/ha of liveweight in 2003 and 2004, respectively.
Forage production cost and cattle purchases and the revenues from cattle sales were calculated in dollars per hectare. The following procedure was applied to estimate beef production cost and profit in each production scenarios.
Profit per hectare (P) was determined by subtracting expenditure per hectare (E) from revenue per hectare (R).
P = R - E
Revenue per hectare was calculated as final steer liveweight in kg per hectare (W) times selling price in dollar per kilogram (k).
R = k * W
Expenditure per hectare consisted of adding all operating cost per hectare.
All information regarding forage production costs was collected from farm accounting records for both years of evaluation. Collected information consisted of monthly electricity consumption, maintenance cost for the central pivot irrigation system, fertilizer cost, and labor cost. Labor cost was estimated from the average farm wage rate paid in Oklahoma-Texas Panhandle during each year of study (USDA, 2004). Electricity cost and labor cost were prorated according the frequency and amount of irrigation in each production scenario. Maintenance cost and fertilizer cost were prorated to the whole area under study.
Steers used in the study were provided by a local stocker grower. However, for the current analysis animals were assumed bought at the beginning of each grazing trials
144 during the summer. Steer cost was estimated as the average weekly steer price reported
for the Texas Panhandle region at the beginning of each summer trials was considered
(Cattle Fax, 2005). The steer weight and price reported by Cattle Fax that most closely
matched the initiation of the grazing trials and steers average initial weight was selected.
The 2003 grazing trial began in July 7; therefore, the price reported in the first week of
July 2003 for steers with average weight of 204 kg was used as the purchase price. The
second year, the grazing trial began in June 5, 2004, and the price reported in the first
week of June 2004 for steers with average weight of 204 kg was considered as the buying
price. Selected buying prices were $2.38 and $2.87 per kg for 2003 and 2004,
respectively, for steers with the average liveweight already mentioned. In addition to the
steer liveweight purchase cost other expenses were included. The interest rate on steer
purchases, feed cost applied to those scenarios in which whole cottonseed was fed, vet
and medicine cost, and minerals cost. The interest rate on steers purchased was estimated
from the average fixed interest rates on farm loans from the Agricultural Finance
Databook (Federal Reserve Bank of Dallas, 2004) for feeder cattle loans for the third
quarter of 2003 and second quarter in 2004. In the first year a 7.4% annual interest rate
for a length of 88 days was applied to the steer purchase cost. During the second year a
7.2% annual interest rate was applied for a length of 84 days to the steer purchase cost.
Whole cottonseed and vet supplies costs were prorated in the whole area of study.
To estimate revenue from cattle sales, similar procedures used in steer buying
price were followed. It was assumed that steers were sold at the end of each grazing trial
after 86 days of summer grazing. Steer prices reported by the US weekly report were
145 taken into account as well. The first year, the grazing trial ended in October 4, and the
price reported in the first week of October 2003 was used for steers with an average
weight of 250 kg was used as the selling price. The second year the grazing trial ended
August 28, 2004. The price reported in the last week of August for that year and for
steers weighting an average of 295 kg was used as selling price. Selected selling prices
were $2.36 and $2.72 per kg for 2003 and 2004, respectively.
Results and discussion
The amount of rainfall and irrigated water applied during summer 2003 and 2004
varied considerably. During summer 2003, total water availability in HI scenarios was
192 mm, for LI scenarios 116 mm, and for NI scenarios 14.7 mm. In contrast, in summer
2004 rainfall was abundant relative to the prior summer. Total water availability in
summer 2004 (rainfall plus irrigation) was 396, 320, and 218 mm for HI, LI, and NI
scenarios, respectively.
Beef production cost varied widely across beef production scenarios during 2003
(Figure 6.1). The lowest beef production cost was $0.62/kg in the NI-NS scenario.
Dryland beef production cost without supplement was two times lower than production cost in the HI-S, HI-NS, LI-S and LI-NS scenarios. Moreover, dryland beef production cost with supplement was 1.5 times higher than in the NI-S scenario. Higher profit/ha corresponded to the lower beef production costs (Figure 6.2). Higher profit per ha was
obtained in the NI-NS scenario. In this scenario profit was 17% higher than in NI-S
146 scenario. When NI-NS was compared to the irrigation scenarios profit was at least 72%
higher.
Several factors may account for this outcome during 2003. First, operating costs in the irrigated and supplemented scenarios were elevated due to high energy and supplement input use (Table 6.1). In the LI-S and HI-S scenarios, energy plus supplement cost were $92.24 and $119.84 of the total operating costs, representing 46 and 53% of costs, respectively. In addition, in LI-NS and HI-NS, energy cost accounted for $54.60 and $90.36 of total costs, representing 34 and 46%, respectively. Secondly, weight gain was les under irrigated and supplement conditions (Table A.15).
During 2004, beef production cost showed similar tendency in regard to previous
year (Figure 6.3). In the second year, similar to previous year, beef production cost in the
NI-NS scenario was the lowest. Beef production cost under dryland conditions without
supplement was 1.5 times lower than in the LI-S, LI-NS, HI-S, and HI-NS scenarios.
Scenario NI-NS also had 1.2 times lower production cost than NI-S. During 2004, profit
per ha was similar in all irrigated beef production scenarios (Figure 6.4). In contrast,
profit per ha in the dryland beef production scenario with supplement was 8 and 14%
higher than other scenarios, respectively. Similar to the previous year, the cost of energy
in 2004 represented the highest operating cost in all irrigation scenarios (Table 6.2).
Fertilizer cost was the second highest cost. The 2004 beef production scenarios were
similar in profitability to the 2003 scenarios (Table A.16). In contrast to 2003, steers
under the irrigated scenarios had better weight gain in 2004. Favorable rainfall
conditions may have enhanced steer performance during the second year.
147 In both years all production scenarios that involved supplement showed higher weight gain per ha than production scenarios without supplement. However, it was not
reflected in better profit per ha; the revenue from weight gain under supplement scenarios
was not sufficient to cover the cost of the supplement. Whole cottonseed cost in both
years represented 20% of the total operating cost. Other operating costs involved in the
beef production such as maintenance, interest rate in steers, labor, vet and medicine, and
minerals cost showed no great variation between production scenarios. These costs did
not have a significant effect on profit per ha in either year.
Profit per hectare under 2003 and 2004 operating conditions was analyzed using
different cattle purchasing and selling prices (Table 6.3 and Table 6.4). Buying and selling steer prices were taken from the weekly US steer report of Cattle Fax for the
Texas Panhandle region. When the buy/sell price differential increases, profit per ha decreases. Moreover, as price differential approaches 17% profit/ha dramatically decrease and start showing negative values. In both years of this study, the price differential was negligible; therefore, profit per ha was positive in all production scenarios. These results agreed with Peel (2000) cited by Phillips et al. (2003) and
Bransby (1989) that mentioned that buying and selling price differential is the most important factor in determining profitability of the stocker enterprise. They concluded that income comes from initial steer weight and weight gained during the grazing trial. In addition, during summer 2003 and 2004, buying and selling prices registered in the Texas
Panhandle region were considered high. Ethridge et al. (1987) recommended that under high buying and high selling price, the most profitable alternative is to stock steers with
148 average initial weight of 181 kg from June to August in Old World bluestem pasture. In this study, all of these conditions coincided and results strongly supported the Ethridge et al. (1987) findings.
These results showed that under dryland conditions stocker steer operations
grazing WW-B.Dahl pasture is profitable. Thus, this production system may save
underground water in the Texas High Plains region (Terrell and Johnson 1999; Johnson
et al., 2004). Additionally, the two year average profit per ha in the NI-NS scenario was
$264/ha. It was not far from results result reported by Allen et al. (2005) for cotton
monoculture under irrigated conditions ($310.00) in New Deal, Texas. In both studies,
only operating costs were considered. However, WW-B.Dahl pastures are less labor
intensive and require less investment in machinery and equipment. These pastures also do not demand chemical applications to prevent and control diseases, and are less
vulnerable to weather risk.
Conclusions
Results from the economic analysis performed for the alternative irrigation-
supplement scenarios showed that grazing yearling steer in WW-B.Dahl pasture in
summer under dryland conditions appears to be the most profitable. The use of whole
cottonseed as energy supplement to enhance beef production seemed to be not cost
effective. Furthermore, current steer marketing conditions during the two year study appeared to influence the profitability of the stocker operation. In both years the differential between buying and selling price was minimal. Incorporation of WW-B.Dahl
149 under dryland conditions into the forage/beef production system in the Texas High Plains
may be a good alternative to reduce underground water consumption for irrigation.
Moreover, the gradual change from traditional irrigated crops to warm season perennial
forages such as WW-B.Dahl may bring sustainability to the agricultural sector and regional economy.
150
1.4
1.2
1.0
0.8
0.6
0.4 Beef production cost ($/kg )
0.2
0.0 LI-S LI-NS HI-S HI-NS NI-S NI-NS Beef production scenario
Figure 6.1 Beef production cost ($/kg) in six combinations of irrigation-supplement scenarios in a WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2003. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation- supplement, and NI-NS no irrigation-no supplement.
151
350
300
250
200
150 Profit ($/ha)
100
50
0 LI-S LI-NS HI-S HI-NS NI-S NI-NS Beef production scenario
Figure 6.2 Profit per hectare ($/ha) in six combinations of irrigation-supplement scenarios in a WW-B.Dahl (Bothriochloa bladhii) pasture grazed by steers in summer 2003. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation- supplement, and NI-NS no irrigation-no supplement
152
1.4
1.2
1.0
0.8
0.6
0.4 Beef production cost ($/kg)
0.2
0.0 LI-S LI-NS HI-S HI-NS NI-S NI-NS Beef production scenario
Figure 6.3 Beef production cost ($/kg) in six combinations of irrigation-supplement scenarios in a WW-B.Dahl (Bothriochloa bladhii) pasture under summer grazing in 2004. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation- supplement, and NI-NS no irrigation-no supplement
153
275
225
175
Profit ($/ha) Profit 125
75
25 LI-S LI-NS HI-S HI-NS NI-S NI-NS Beef production scenario
Figure 6.4 Profit per hectare ($/ha) in six combinations of irrigation- supplement scenarios in a WW-B.Dahl (Bothriochloa bladhii) pasture grazed by steers in summer 2004. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation- supplement, and NI-NS no irrigation-no supplement
154
Table 6.1 Beef production costs and revenue in 2003 in six combinations of irrigation- supplement scenarios in a WW-B.Dahl (Bothriochloa bladhii) pasture. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation- supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement.
Beef production scenario Item LI-S LI-NS HI-S HI-NS NI-S NI-NS ------$/ha------
Energy 53.78 54.60 88.30 90.36 18.77 16.66 Fertilizer 37.97 37.97 37.97 37.97 37.97 37.97 Whole cottonseed 38.46 0.00 31.54 0.00 44.71 0.00 Interest rate in 20.83 20.47 17.92 19.37 24.46 20.58 steer cost
Maintenance 15.52 15.52 15.52 15.52 15.52 15.52 Vet and medicine 16.65 14.95 13.65 14.67 19.35 15.91 Labor 15.50 12.59 19.00 16.90 11.28 4.62 Minerals 1.95 2.19 2.00 2.15 2.84 2.33 Revenue 194.67 165.64 198.12 152.97 261.37 305.95
155
Table 6.2 Beef production cost and revenue in 2004 in six combinations of irrigation- supplement scenarios in a WW-B.Dahl (Bothriochloa bladhii) pasture. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation- supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement
Beef production scenario Item LI-S LI-NS HI-L HI-NS NI-S NI-NS ------$/ha------
Energy 42.43 43.08 76.52 78.30 9.14 8.11 Fertilizer 41.28 41.28 41.28 41.28 41.28 41.28 Whole cottonseed 29.73 0.00 36.98 0.00 29.13 0.00 Interest rate in 18.49 19.94 23.29 27.24 18.67 18.28 steer cost
Maintenance 15.52 15.52 15.52 15.52 15.52 15.52 Vet and medicine 10.89 11.05 13.65 15.37 10.75 10.82 Labor 16.14 13.11 19.78 17.60 11.74 4.81 Minerals 1.22 1.55 1.91 2.15 1.51 1.51 Revenue 215.16 212.18 212.34 203.16 241.24 222.89
156
Table 6.3 Profit per hectare ($/ha) in selected buying and selling prices in six combinations of irrigation-supplement scenarios in operation conditions in 2003. Buying price is based on 204 kg steer liveweight. Selling price is based on 250 kg steer liveweight. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement
Beef production scenario Buying Selling Price LI-S LI-NS HI-S HI-NS NI-S NI-NS Price ($/kg) ($/kg) ------Profit ($/ha)------2.39 45.54 25.11 62.02 15.95 88.85 155.90 2.14 2.48 -57.79 -73.96 -30.06 -79.45 -31.42 52.69 2.05 2.17 -36.18 -47.25 -18.59 -57.85 -3.67 71.60 1.85 2.38 194.67 165.64 198.12 152.97 261.37 305.95 2.36
157
Table 6.4 Profit per hectare ($/ha) in selected steer buying and selling prices in six combinations of irrigation-supplement scenarios in operation conditions in 2004. Buying price is based on 204 kg steer liveweight. Selling price is based on 295 steer liveweight. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement
Beef production scenario Buying Selling Price LI-S LI-NS HI-S HI-NS NI-S NI-NS Price ($/kg) ($/kg) ------Profit ($/ha)------2.30 48.12 48.68 15.24 2.77 76.65 74.25 2.01 2.48 16.32 12.74 -26.13 -48.60 44.13 41.19 2.08 2.21 -37.41 -38.41 -88.37 -109.09 -8.45 -5.20 1.79 2.37 114.03 115.78 95.08 88.94 142.23 135.46 2.18 2.87 215.16 212.18 212.34 203.16 241.24 222.89 2.72
158 References
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160 CHAPTER VII
OVERALL DISCUSSION AND IMPLICATIONS
Overall discussion
Old World Bluestem species were brought to the United States from Europe and
Asia and are well adapted to the Southern High Plains environmental conditions (Dabo et al., 1988; McCollum 2000). WW-B. Dahl, formerly known as WW-857, and most recently released cultivar was originally collected in Manali, India. In 1960 it was brought to the Southern Plains Research Station in Woodward, Oklahoma. After 15 years of adaptation and production trials, WW-857 was selected and finally developed into WW-B. Dahl and released in 1994 by the USDA-ARS, USDA-SCS, Texas Tech
University, and the Texas Agricultural Experimental Station (Bell and Caudle, 1994;
Dewald et al., 1995).
In the Texas High Plains, Old World bluestems have been considered as an
alternative to reduce water withdrawals from the Ogallala aquifer due to drought
tolerance and promising forage potential (Dabo et al., 1988; McCollum 2000; Hodges
and Bidwell, 1993). Investigation on forage potential of WW-B.Dahl had been
documented (Villalobos et al., 2000a; Villalobos et al., 2002; Bezanilla, 2002; Philipp,
2004; Allen et al., 2005). Summer grazing studies evaluating levels of irrigation and
feeding energy in WW-B.Dahl pastures are lacking.
Results of my study suggest that forage yield and quality in WW-B.Dahl appear to be related to morphological and physiological aspects of the plant rather than water
161 availability during the growing season. For example, Philipp (2004) observed that as irrigation gradient increases leaf:stem ration in WW-B.Dahl decreases, resulting in crude protein loss. Jensen et al. (2003) and Asay et al. (2002) concluded that digestibility of grasses is not influenced by changes in moisture conditions.
Although forage quality in terms of crude protein was below minimal requirements for growing steers (Villalobos and Richardson, 1998) during both years of evaluation steer performance was acceptable. In vitro dry matter digestibility values were high in both years, suggesting that even though protein content was low energy was sufficient to enhance steer performance. Evidence from my data of forage standing crop in WW-B.Dahl grass across irrigation levels suggests that forage availability was adequate to meet steers forage demand. Therefore, my results agree with the research conducted by (Brown, 1995), (Svejcar and Christiansen, 1987), (Masters and Britton,
1988), (Coyne et al.,1995), (Owensby et al.,1999), and Derner et al.,2001) in other Old
World bluestems and (Philipp, 2004) in WW.B.Dahl. They reported that plants under water stress and defoliation conditions had a better response than plants under irrigated and without defoliation. In regard to the use of supplement the amount of whole cottonseed feed during the trials was not adequate to enhance beef production.
A relationship between irrigation levels and forage utilization was not found in my study. Regrowth from WW-B.Dahl under diverse moisture conditions throughout the growing season support the previous findings. Further, methodology used to measure forage utilization in WW-B.Dahl may influence my results.
162 Variation on water availability between beef production scenarios, in both years
of evaluation was evident. Results from the economical analysis suggested that beef
production under dryland conditions in WW-B.Dahl pasture is a profitable activity.
Implications
Information from my study suggested that WW-B.Dahl grass performs well under
dryland conditions in the Texas High Plains. According to my results, WW-B.Dahl
maintains adequate forage yield and sufficient forage quality under limited moisture
conditions. Therefore, WW-B.Dahl can support moderate stocking rate during the
growing season. Beef production systems based on native grassland may be
complemented with WW-B.Dahl pastures in this region. This recommendation is
supported by the results obtained from economic analysis performed in all production scenarios. My results showed that producing beef in WW-B.Dahl pasture during summer under dryland conditions is a profitable activity in The Texas High Plains. Further investigation should be carried out to measure quality of leaf and stem in WW-B.Dahl under grazing conditions. Research also is needed in the area of protein and dry matter digestibility at ruminal level.
163
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177
APPENDIX
178
Table A.1 Analysis of variance for forage standing crop in 2003.
Source DF SS MS F P-Value Test
Irrigation 2 2422.9873 1211.4936 3.08 0.0495 EE(a)
EE(a) 117 45968.7204 392.8950
Period 2 22635.1243 11317.5622 24.79 <.0001 EE(b)
P*I 4 29584.9852 7396.2463 16.20 <.0001 EE(b)
EE(b) 234 106814.3625 456.4716
Corr. Total 359 207426.1797
Table A.2 Analysis of variance for forage standing crop in 2004.
Source DF SS MS F P-Value Test
Irrigation 2 4679.6928 2339.8469 20.97 <.0001 EE(a)
EE(a) 117 13055.4863 111.5853
Period 2 27.8419 13.9209 0.05 0.9221 EE(b)
P*I 4 4758.5881 1189.6470 4.18 0.0056 EE(b)
EE(b) 234 66622.2579 284.7105
Corr. Total 359 89143.8670
179
Table A.3 Analysis of variance for forage crude protein content in 2003.
Source DF SS MS F P-Value Test
Irrigation 2 1.8849 0.9424 1.31 0.2917 EE(a)
EE(a) 21 15.1386 0.7208
Period 2 7.9693 3.9846 10.91 0.0002 EE(b)
P*I 4 9.1118 2.2779 6.24 0.0005 EE(b)
EE(b) 42 15.3344 0.3651
Corr. Total 71 49.4390
Table A.4 Analysis of variance for forage crude protein content in 2004.
Source DF SS MS F P-Value Test
Irrigation 2 33.0876 16.5438 17.26 <.0001 EE(a)
EE(a) 21 20.1236 0.9582
Period 2 41.3188 20.6594 45.94 <.0001 EE(b)
P*I 4 11.0042 2.7510 6.12 0.0006 EE(b)
EE(b) 42 18.8880 0.4497
Corr. Total 71 124.4222
180
Table A.5 Analysis of variance for forage in vitro dry matter digestibility in 2003.
Source DF SS MS F P-Value Test
Irrigation 2 7.5284 3.7642 0.24 0.788 EE(a)
EE(a) 21 328.0516 15.6215
Period 2 233.4760 116.7380 4.79 0.0133 EE(b)
P*I 4 231.8263 57.9565 2.38 0.0669 EE(b)
EE(b) 42 1022.9532 24.3560
Corr. Total 71 1823.8355
Table A.6 Analysis of variance for forage in vitro dry matter digestibility in 2004.
Source DF SS MS F P-Value Test
Irrigation 2 7.0828 3.5414 0.32 0.7322 EE(a)
EE(a) 21 235.0335 11.1920
Period 2 16.2942 8.1471 0.71 0.4975 EE(b)
P*I 4 9.8921 2.4730 0.22 0.9284 EE(b)
EE(b) 42 482.0562 11.4775
Corr. Total 72 750.3588
181
Table A.7 Analysis of variance for forage neutral digestible fiber in 2003.
Source DF SS MS F P-Value Test
Irrigation 2 2.4860 1.2430 0.08 0.9249 EE(a)
EE(a) 21 333.0940 15.8616
Period 2 267.8607 133.9303 5.30 0.0088 EE(b)
P*I 4 194.3762 48.5940 1.92 0.1241 EE(b)
EE(b) 42 1060.4033 25.2476
Corr. Total 71 1858.2202
Table A.8 Analysis of variance for forage neutral digestible fiber in 2004.
Source DF SS MS F P-Value Test
Irrigation 2 9.1254 4.5627 0.41 0.6680 EE(a)
EE(a) 21 232.9909 11.0948
Period 2 16.3177 8.1588 0.72 0.4942 EE(b)
P*I 4 13.8907 3.4726 0.31 0.8729 EE(b)
EE(b) 42 478.0575 11.3823
Corr. Total 71 750.3822
182
Table A.9 Analysis of variance for steer performance (average daily gain per head) in 2003.
Source DF SS MS F P-value Test
Irrigation 2 0.1010 0.0504 4.74 0.0583 EE(a)
Supplement 1 0.0322 0.0322 3.03 0.1324 EE(a)
I*S 2 0.1318 0.0660 6.18 0.0348 EE(a)
EE(a) 6 0.0640 0.0106
Period 2 0.9571 0.4785 17.37 0.0003 EE(b)
P*I 4 0.0860 0.0215 0.78 0.5590 EE(b)
P*S 2 0.0106 0.0053 0.19 0.8275 EE(b)
P*I*S 4 0.0250 0.0062 0.23 0.9186 EE(b)
EE(b) 12 0.3306 0.0275
Corr. Total 35 1.7383
183
Table A.10 Analysis of variance for steer performance (average daily gain per head) in 2004.
Source DF SS MS F P-value Test
Irrigation 2 0.0930 0.0464 3.10 0.1188 EE(a)
Supplement 1 0.1401 0.1401 9.36 0.0223 EE(a)
I*S 2 0.0049 0.0024 0.16 0.8520 EE(a)
EE(a) 6 0.0899 0.0149
Period 2 0.7832 0.3916 30.95 <.0001 EE(b)
P*I 4 0.1025 0.0256 2.03 0.1547 EE(b)
P*S 2 0.0032 0.0016 0.13 0.8801 EE(b)
P*I*S 4 0.0527 0.0131 1.04 0.4254 EE(b)
EE(b) 12 0.1518 0.0126
Corr. Total 35 1.4213
184
Table A.11 Analysis of variance for steer performance (daily gain per ha) in 2003.
Source DF SS MS F P-value Test
Irrigation 2 6.9230 3.4650 0.44 0.6611 EE(a)
Supplement 1 1.7945 1.7945 0.23 0.6487 EE(a)
I*S 2 4.8754 2.4377 0.31 0.7431 EE(a)
EE(a) 6 46.8590 7.8098
Period 2 34.5399 17.2699 23.67 <.0001 EE(b)
P*I 4 5.1015 1.2753 1.75 0.2041 EE(b)
P*S 2 0.2804 0.1402 0.19 0.8276 EE(b)
P*I*S 4 0.9403 0.2351 0.32 0.8577 EE(b)
EE(b) 12 8.7543 0.7295
Corr. Total 35 110.0683
185
Table A.12 Analysis of variance for steer performance (daily gain per ha) in 2004.
Source DF SS MS F P-value Test
Irrigation 2 1.6160 0.8080 0.08 0.9209 EE(a)
Supplement 1 5.1950 5.1950 0.54 0.4914 EE(a)
I*S 2 2.5207 1.2603 0.19 0.8803 EE(a)
EE(a) 6 58.0679 9.6779
Period 2 34.9934 17.4967 21.19 0.0001 EE(b)
P*I 4 5.2192 1.3048 1.58 0.2424 EE(b)
P*S 2 0.2749 0.1374 0.17 0.8486 EE(b)
P*I*S 4 2.9314 0.7328 0.89 0.5005 EE(b)
EE(b) 12 9.9091 0.8257
Corr. Total 35 120.7276
186
Table A.13 Analysis of variance for forage utilization in 2003.
Source DF SS MS F P-value Test
Irrigation 2 189.9419 94.9709 0.80 0.4938 EE(a)
Supplement 1 116.7480 116.7480 0.98 0.3609 EE(a)
I*S 2 1806.5989 903.2994 7.57 0.0229 EE(a)
EE(a) 6 716.2088 119.3681
Period 2 1939.7120 969.8560 12.86 0.0010 EE(b)
P*I 4 217.6181 54.4045 0.72 0.5937 EE(b)
P*S 2 107.3256 53.6628 0.71 0.5105 EE(b)
P*I*S 4 1198.3703 299.5925 3.97 0.0280 EE(b)
EE(b) 12 905.0530 75.4210
Corr. Total 35 7197.5766
187
Table A.14 Analysis of variance for forage utilization in 2004.
Source DF SS MS F P-value Test
Irrigation 2 682.5793 341.2896 1.51 0.2950 EE(a)
Supplement 1 264.4201 264.4201 1.17 0.3215 EE(a)
I*S 2 499.7045 249.8522 1.10 0.3909 EE(a)
EE(a) 6 1359.2519 226.5420
Period 2 2856.8540 1428.4270 10.04 0.0027 EE(b)
P*I 4 1361.2731 340.3182 2.39 0.1085 EE(b)
P*S 2 277.5582 138.7791 0.98 0.4049 EE(b)
P*I*S 4 1055.5967 263.8991 1.86 0.1832 EE(b)
EE(b) 12 1706.6837 142.2236
Corr. Total 35 10063.9215
188 Table A. 15 Estimation of beef production cost ($/kg) and profit ($/ha) in six combinations of irrigation-supplement scenarios in a WW-B.Dahl pasture grazed by steers in summer 2003. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement.
Beef production scenarios Variable Unit LI-S LI-NS HI-S HI-NS NI-S NI-NS
Operational cost $/ha 200.66 158.29 225.90 196.94 174.90 113.59 (O) Weight gain kg/ha 171.61 141.29 183.19 152.08 189.68 181.83 (G) Beef prod. cost $/kg 1.17 1.12 1.23 1.29 0.92 0.62 C=O/G
Steer expenditure $/ha 1,151.58 1,131.62 990.52 1,070.77 1,352.36 1,137.95 (SE) Operational cost $/ha 200.66 158.29 225.90 196.94 174.90 113.59 (O) Expenditure $/ha 1,352.24 1,289.91 1,216.42 1,267.71 1,527.26 1,251.54 E=SE+O
Steer revenue $/ha 1,546.91 1,455.54 1,414.54 1,420.68 1,788.63 1,557.50 (I)
Profit $/ha 194.67 165.64 198.12 152.97 261.37 305.95 P=I-E
189 Table A. 16 Estimation of beef production cost ($/kg) and profit ($/ha) in six combinations of irrigation-supplement scenarios in a WW-B.Dahl pasture grazed by steers in summer 2004. LI-S low irrigation–supplement, LI-NS low irrigation–no supplement, HI-S high irrigation-supplement, HI-NS high irrigation-no supplement, NI-S no irrigation-supplement, and NI-NS no irrigation-no supplement.
Beef production scenarios Variable Unit LI-S LI-NS HI-S HI-NS NI-S NI-NS
Operational cost $/ha 175.69 145.52 228.94 197.47 137.74 100.33 (O) Weight gain kg/ha 164.84 154.31 188.87 178.45 160.68 139.73 (G) Beef prod. cost $/kg 1.07 0.94 1.21 1.11 0.86 0.72 C=O/G
Steer expenditure $/ha 1,100.37 1,186.88 1,386.25 1,621.61 1,111.30 1,087.85 (SE) Operational cost $/ha 175.69 145.52 228.94 197.47 137.74 100.33 (O) Expenditure $/ha 1,276.06 1332.40 1615.19 1819.07 1249.04 1411.07 E=SE+O
Steer revenue $/ha 1,491.22 1,544.58 1,827.53 2,022.23 1,490.28 1,411.07 (I)
Profit $/ha 215.16 212.18 212.34 203.16 241.24 222.89 P=I-E
190