MP434

Management of Hay Production n by Dr. Dirk Philipp and Dr. John A. Jennings

DIVISION OF AGRICULTURE RESEARCH & EXTENSION University of Arkansas System

University of Arkansas, U.S. Department of Agriculture, and County Governments Cooperating Table of Contents

Introduction ...... 5 Hay Testing and Interpretation of Results ...... 5 Visual Appraisals of Hay Quality ...... 7 Mowing, Wilting and Baling Hay Crops ...... 8 Spontaneous Heating ...... 12 DM Recovery in Heated Hays ...... 15 Nutritional Characteristics of Heated Hays ...... 16 Weathering Effects ...... 19 Cautions for Fertilization ...... 22 Other Toxic Substances in Hay ...... 23 Summary ...... 25 to test all hay for nutrient value. A representative sample of the Introduction Estimating the nutritive value of hay hay available for feeding should be from theoretical values or visual submitted for analysis before the hay The production and storage of evaluation only will lead to errors in feeding period. The University of hay is an integral component of feeding. This results in reduced Arkansas Agricultural Services many livestock enterprises in animal performance, costly errors in Laboratory will analyze samples Arkansas. Some producers maintain under- or overfeeding, and loss of submitted through Cooperative a full line of hay equipment and potential profit. Extension Service offices, or samples produce large quantities of hay; may be sent to a private laboratory. others prefer to purchase hay to meet Nutrient composition data In some cases, an analysis may be their needs. An understanding of the from the University of Arkansas provided by a feed company. processes involved in harvesting and Cooperative Extension Service storing hay is critical to the success Forage Database is used here to A routine hay analysis usually of hay feeding. This publication will illustrate the variability in nutrient includes (1) moisture or dry matter discuss the management of hay content of hays (Table 1). The data­ (DM) content, (2) crude protein (CP) production, measures or indicators of base contains nutrient composition and (3) analysis of structural plant forage nutritive value, toxic sub ­ values for more than 3,000 samples fiber that may be reported as crude stances in hays, hay sampling, hay of bermudagrass hay. The crude fiber, acid detergent fiber (ADF) or analysis and ration formulation. protein (CP) values of bermudagrass neutral detergent fiber (NDF). Most hays ranged from 3.7 to 23.7 commonly, both ADF and NDF are percent, and total digestible nutri­ reported; crude fiber is a remnant of Hay Testing and ents (TDN) ranged from 40 to 81 the old proximate analysis system percent. These data and other values and is rarely used today. Concentra­ Interpretation of Results shown in Table 1 indicate that it is tions of net energy or TDN are futile to attempt to estimate the calculated using prediction equations Hay Analysis. The first step in nutrient content of hay. Any efficient based on CP and fiber levels. developing a hay feeding program hay feeding program will start with Mineral levels can be obtained that optimizes livestock production is hay sampling and analysis. from additional tests.

Table 1. The percentages and ranges of dry matter (DM), crude protein (CP), total digestible nutrients (TDN), calcium (Ca) and phosphorus (P) of Arkansas hays (DM basis).

Number DM CP TDN Ca P Hay Samples1 Avg2 (Range)3 Avg (Range) Avg (Range) Avg (Range) Avg (Range) Alfalfa 364 88 (63-95) 18.5 (6.1-33.1) 61 (37-78) 1.25 (.56-2.07) .31 (.19-.43) Bahiagrass 173 88 (72-94) 9.6 (4.1-17.6) 57 (46-77) .49 (.30-1.07) .21 (.10-.32) Bermudagrass 2,979 87 (61-97) 12.4 (3.7-23.7) 60 (40-81) .51 (.10-1.21) .28 (.08-.61) Bluestem 57 87 (66-94) 9.4 (2.6-15.6) 56 (37-71) .49 (.32-.64) .28 (.18-.40) Bromegrass 29 88 (79-93) 10.7 (3.9-27.4) 56 (50-65) .63 (.45-.78) .10 (.08-.12) Clover 45 87 (68-93) 14.0 (6.1-21.3) 56 (31-66) 1.12 (.55-1.93) .27 (.09-.50) Dallisgrass 32 89 (80-94) 10.8 (6.3-20.4) 58 (42-79) .55 (.51-.58) .26 (.22-.30) Fescue 906 87 (64-97) 11.2 (3.9-22.4) 54 (42-70) .50 (.24-.85) .30 (.11-.51) Johnsongrass 123 85 (63-94) 11.0 (4.0-21.7) 62 (48-73) .57 (.22-1.01) .32 (.19-.48) Legume/grass mix 200 87 (63-94) 12.6 (5.6-26.6) 55 (41-71) .78 (.30-1.32) .28 (.11-.47) Mixed grass 2,376 87 (60-99) 11.1 (2.1-24.8) 53 (35-72) .58 (.12-3.06) .30 (.04-.66) Orchardgrass 157 87 (62-95) 13.5 (6.3-23.6) 57 (45-68) .51 (.16-.92) .34 (.17-.49) Ryegrass 195 87 (64-96) 11.8 (3.9-26.7) 56 (45-68) .50 (.26-1.15) .29 (.10-.53) Sudangrass 254 84 (65-95) 11.6 (2.5-20.2) 62 (42-83) .69 (.36-.96) .31 (.21-.43) Wheat 66 87 (68-93) 11.3 (4.4-19.4) 55 (38-68) .43 (.36-.53) .38 (.23-.48) 1 Indicates the number of samples in the database which were averaged for CP and TDN values. Fewer samples were analyzed for calcium and phosphorus. 2 Average value. Values for DM and TDN were rounded to the nearest whole number. 3 Range indicates the lowest and highest value observed. Range values for DM and TDN were rounded to the nearest whole number.

5 In most situations, cattle diets samples for analysis. A publication Likewise, the TDN value of the hay are formulated to meet require­ entitled Beef Cattle Nutrition (54 percent) is greater than the ments for CP and energy (TDN or Series, Part 3: Nutrient TDN requirement (52.1 percent), so net energy), assuming adequate Requirement Tables, MP391, is no supplemental energy is needed. feed intake. If a mineral deficiency, available at University of Arkansas imbalance or toxicity is suspected, Cooperative Extension Service Supplementation is needed, a mineral analysis should also be offices. For beef cattle, hay test however, for the lactating beef cow requested. results should be interpreted by fed this hay. The requirements using values in that publication. for CP (10.9 percent) and TDN Hay Sampling. Inaccurate (60.4 percent) are greater than the sampling of hay may lead to even For example, the following nutrients in the hay (9 percent CP greater errors than using average routine hay test shows nutrient and 54 percent TDN). Therefore, values from hay composition values on an “as-fed” and DM basis. both supplemental protein and tables. A “lot” of hay is defined as To determine whether the hay needs energy (TDN) would be required. In the entire amount of hay cut from to be supplemented with either a CP this case, the amount of supplement one field at one time. All hay in the or energy (TDN) supplement, use needed to meet the nutrient needs of lot should have been cut at the the DM basis column on the hay the lactating cows could be deter­ same stage of maturity, wilted analysis report. A typical hay mined with a computerized ration under the same climatic conditions analysis follows. formulation program or by manual and stored such that weathering calculation. Other nutrient deficien­ HAY ANALYSIS effects were the same. Each lot of cies (calcium, phosphorus, trace hay should be sampled and Chemical As-Fed DM minerals, etc.) in hay can be deter­ analyzed independently. Composition Basis Basis mined by using the same procedure. Hay can be most accurately Moisture 12.0% DM 88.0% Using hay analysis results sampled using a bale core sampler. CP 7.9% 9.0% to match hay to cattle needs. A minimum of ten core samples, TDN 47.5% 54.0% Most cattle producers bale or one per bale, should be collected purchase several lots of hay for from each lot of hay. Core samples The CP and TDN requirements feeding their animals. Due to should be taken from the end of for 1,100-pound mature beef cows environmental conditions and other conventional rectangular bales and as shown in MP391 are as follows: factors, hay quality often varies. from the round side of round bales Analysis can be used to designate and stacks. Angle the core-sampling NUTRIENT REQUIREMENTS the highest quality hay for the cattle tool in an upward direction when Diet Nutrient Density, with the highest nutrient needs and sampling bales stored outside. This DM Basis the lowest quality hay for animals CP TDN will avoid creating a passageway with the lowest nutrient needs. for water to enter the inside of the Beef cows, 11 mo. since By matching hay to the nutrient bale and rain will not enter it. In calving (last ¹/³ pregnancy) 7.7% 52.1% needs of cattle, hay is used more most Arkansas counties, county Beef cows, 2 mo. since efficiently, overfeeding and under­ extension agents have sample calving, 20 lb peak milk 10.9% 60.4% feeding errors are reduced, less bags, sampling equipment and supplement is needed, cattle information on obtaining hay To properly interpret the hay performance is usually improved analysis for a 1,100-pound mature and profit potential is increased. beef cow at 11 months after calving (last one-third of pregnancy), com­ Hay quality of different pare the CP value of the hay on a forage species. The primary DM basis to the nutrient requirement. forages used for hay throughout The hay contains 9 percent CP, and Arkansas are fescue, bermudagrass the cow requires 7.7 percent. The and mixed grasses. Several other hay has a higher level of CP than forage species are used to a lesser required. Therefore, no protein extent (Table 1). Only two forages, supplement is needed when this hay bluestem and bahiagrass, had Proper sampling technique for is fed free-choice to these beef cows CP values that averaged below round bales. during the last third of pregnancy. 10 percent. Alfalfa hay averaged

6 over 14 percent CP. Generally, beef forage variety do influence hay after storage, individual bale flakes cows require a diet containing less quality, but other factors have a also may be difficult to pull apart. than 12 percent CP, but growing similar or greater effect. In the cattle, especially lightweight calves, absence of a hay test, certain visual Purity. Hay purity is simply an observation of the relative propor­ often need more than 12 percent CP. characteristics of baled hay can help tion of weeds or foreign material in Lactating dairy cows usually need assess relative quality. With experi­ the hay. Certain weeds can decrease higher levels of CP than can be ence, these factors can be judged to the nutritive value of the hay or be provided by many hays. The use help sort different lots of hay into poisonous to livestock. Undesirable of high CP hays by beef cattle groups of poor, average or good weeds easily can be established by generally results in inefficient use quality. Characteristics that should feeding weedy hay pur chased off the of protein. be considered when visually evalu­ farm. High weed content can be the ating hay are forage maturity, In hays produced in Arkansas, result of low soil fertility or other condition, purity, color and smell. poor production practices. Foreign energy (expressed as TDN) is the Once hay is purchased, it should be material such as dead forage matter, most common limiting factor for sampled and analyzed so that a sticks and trash also can reduce hay beef cattle. The average TDN values feeding program can be developed. shown for hays in Table 1 would quality and acceptability. often be satisfactory for beef cattle, Maturity. Forage maturity at Color. Color probably has the but the lowest quality hays (at the harvest has greater influence on hay biggest influence on sale price at hay bottom of the range) would need quality than any other single factor. markets and in private sales, and it to be supplemented with TDN, Forages that become too mature easily biases visual appraisals. before cutting have high concentra­ especially for growing and Although it can give an indication of tions of fiber that result in poor lactating cattle. harvest and storage conditions, color digestibility. Mature, high-fiber is not a strong indicator of hay forages have lower CP and TDN quality! Yellow or bleached hay may Visual Appraisals of levels than forages cut at less mature indicate poor harvest conditions, stages of growth. Some indicators of advanced forage maturity or a desirable forage maturity include: Hay Quality lengthy storage period, but other Can the nutritive value of hay 1) Absence of seedheads and seed factors should be considered before be estimated by simply looking stems (mature blooms for that conclusion is reached. Hay that at it? The short answer is no! legume hay) was cut when wet may become Generally, the CP or TDN content of 2) Small or fine stems bleached in the field, resulting in a forages cannot be estimated by 3) High percentage of leaf that is yellow appearance. This can occur visual appraisal alone. The only way green compared to dead even though tests show it to be to accurately determine the feeding 4) High leaf-to-stem ratio of good nutritive value. Hay that value of a specific lot of hay is by a gets rained on during harvest may Condition. Hay condition refers laboratory analysis. Even if the hay also become bleached in color. to the leafiness and texture of the looks the same as another hay crop, Additionally, research has shown that forage. Condition often reflects the it may have drastically different hay can have better nutritive value if harvest methods and conditions, as nutrient levels. Variation in nutritive it is cut at the right stage of maturity well as forage maturity. Desirable value occurs from year to year, field and gets rained on than other hay that indicators of forage condition include: to field and cutting to cutting due to is harvested at a more mature growth weather, management and several 1) A high leaf-to-stem ratio stage without rain damage. Hay other factors. 2) Small, fine stems stored outside that is exposed to the 3) Large leaves sun also may become bleached; the Unfortunately, laboratory results 4) Intact leaves with little evidence outside of a bale may be yellowed or are often not available when you are of shattering bleached while the interior may still buying hay. The seller may offer an 5) A soft feel or texture be green. Conversely, hay that is assessment of the hay such as, “it bright green in color may have poor was fertilized,” or, “it is that new Legumes that are baled too dry nutritive value if it was harvested at hybrid everybody wants,” but these will often have a large percentage of an advanced stage of growth. A comments really tell you nothing shattered leaves. Hay that is baled brown color inside the bale that is about hay quality. Fertilization or too wet is often very dusty or moldy; coupled with a tobacco-like odor

7 indicates that spontaneous heating combination of desirable visual lower concentrations of CP and has occurred. characteristics will generally be of digestible DM. Unfortunately, the good nutritive value, although a management of forage crops is Smell. The smell or odor of livestock ration cannot be balanced complicated by the need to allow hay is affected by the concentration from visual estimates. When visu­ adequate initial growth, and either of moisture in the hay at baling. A ally appraising hay, more emphasis adequate regrowth or harvest inter­ typical fresh hay odor is desirable. should be placed on maturity, condi­ vals (depending on the crop) to Hay that smells musty or moldy was tion and purity than on color or maintain plant vigor and the health baled at higher than desirable mois­ smell. Visual appraisal is learned by of the stand. Clearly, these ture levels or became wet during experience and by comparing visual competing management concerns storage. Some hays that are baled observation with hay analysis require some compromise. before they are adequately dried results. Hay contests and field days have a tobacco-like odor and are are excellent opportunities to visu­ For alfalfa, the general rule of brown in color. ally compare hay samples with thumb is to harvest before the crop results from laboratory analysis. reaches ¹/10 bloom; however, the Differences in forage Visual appraisals should not be quality characteristics of alfalfa species. As a general rule, cool- relied on for developing a live­ harvested at this growth stage may season grasses have less fiber and stock feeding program. Hay not allow producers to sell to top- higher concentrations of CP than should be tested to determine dollar dairy markets. Bermudagrass warm-season grasses when they are actual forage quality. should generally be harvested in compared at the same stage of intervals of about four weeks during growth. This difference is due to the growing season. Individuals factors of plant physiology and not Mowing, Wilting and wishing to market or feed bermuda­ management decisions. Cool-season grass hay of the highest quality may grasses include ryegrass, cereal Baling Hay Crops reduce this interval by a few days, grains, tall fescue, orchardgrass and but haying intervals of less than smooth bromegrass. Warm-season Harvest timing. No single 22 days are very rare. Tall fescue grasses include bermudagrass, factor affects the quality of hay or bahiagrass, switchgrass and dallis­ silage as much as the maturity of the and other cool-season perennial grass. Both cool- and warm-season forage when the mower is first forages should be harvested at the grasses can have very good quality pulled into the field (Table 2). boot or early heading stages of if harvested at the proper maturity. As plants mature, stem is increased growth. The inter relationships Generally, legumes have higher in the total forage mass, and there­ between maturity, concentrations of nutritive values than most grasses. fore, the leaf-to-stem ratio is fiber (NDF) and digestibility for tall Legumes include annual and peren­ reduced. Increased proportions of fescue are shown in Figure 1. The nial clovers, hairy vetch, lespedeza stem usually result in higher most rapid changes in fiber content and alfalfa. Clover-grass mixtures concentrations of fiber (usually and digestibility occur between the will usually have higher nutritive measured as NDF and ADF) and late boot and early bloom stages of value than grasses grown alone. Table 2. Effects of maturity on forage quality.1 Legumes also can improve the nutri­ tive value of mixed hays harvested Forage CP NDF ADF TDN when the grass component is more ------% of DM ------­ mature than desired. Clover planted Alfalfa hay with fescue or ryegrass can lower Early vegetative 23 38 28 66 nitrogen fertilizer costs and help to Late vegetative 20 40 29 63 maintain good nutritive value if Early bloom 18 42 31 60 harvest is delayed. Midbloom 17 46 35 58 Full bloom 15 50 37 55

Summary. To develop an Bermudagrass hay economical feeding program, there Early vegetative 16.0 66 30 61 is no substitute for hay analysis. In Late vegetative 16.5 70 32 54 the absence of laboratory analysis, 15 - 28 days growth 16.0 74 33 55 visual appraisal of hay can be useful 29 - 42 days growth 12.0 76 38 50 in choosing good hay compared 43 - 56 days growth 8.0 78 43 43 to poor hay. Hay with the best 1 Nutrient Requirements of Dairy Cattle (1989).

8 growth. Producers should make thoroughly during the weeks before within the forage mass. Generally, every effort to harvest these crops at haying season. It is impossible to grasses wilt much faster than the best compromise between nutri­ calculate the tons of hay that have legumes. Some legumes are noto­ tive value and yield. The ideal been damaged because of poorly rious for their slow drying rate; for harvest maturities for various forage maintained equipment that was not instance, red clover dries even crops are summarized in Table 3. field ready at harvest time. slower than alfalfa. For this reason, it is essential that alfalfa and other Mowing and wilting. The The goal during the wilting legumes be conditioned when they mechanics of hay production process is to eliminate water as are mowed. Normally, sickle-bar should begin with a caution to quickly as possible. This conserves type mowers with conditioning check and service all equipment nutrients by limiting respiration rollers are used for this purpose. Generally, disc-type mowers are Figure 1. Digestibility and neutral detergent fiber (NDF) in Kentucky-31 preferred for harvesting bermuda­ tall fescue at various maturities. Source: C. S. Hoveland and N. S. Hill, grass and other perennial grasses. University of Georgia. Many grasses, such as bermuda­ grass, dry rapidly, and the condition ing step can often be omitted. When conditioning alfalfa hay, especially with roller- type conditioners, the risk of crushing blister beetles increases. Crushed blister beetles are lethal to horses con suming these forages; however, the stems of alfalfa plants dry so slowly that there is really no alternative to conditioning with either crushing rollers or a tine-type conditioner.

Table 3. Recommended growth stages or time intervals to harvest various hay crops.1

Forage Time of harvest Alfalfa First cutting: bud stage Second and later cuttings: ¹/10 bloom First cutting following spring seeding: mid to full bloom Orchardgrass, timothy or tall fescue First cutting: boot to early heading Regrowth: four- to six-week intervals Red, arrowleaf or crimson clovers Early bloom Sericea lespedeza 15 to 18 inches Oats, barley, rye, ryegrass or wheat Boot to early heading (nutritive value of rye will deteriorate much faster than other cereal grains after this growth stage is reached) Annual lespedeza Early bloom and before bottom leaves begin to fall off Ladino or white clover Cut at correct stage for companion grass Hybrid bermudagrass First cutting: 15 to 18 inches Second and later cuttings: every four to five weeks (intervals down to 22 days can be used for highest quality) Birdsfoot trefoil Cut at correct stage for companion grass Sudangrass, sorghum-sudangrass and pearl millet 30 to 40 inches

1Ball et al., 1996; Southern Forages, 2nd ed., Potash and Phosphate Institute and Foundation for Agronomic Research, Norcross, GA.

9 Summer annual grasses such as parts of grass plants by mowing too subject to environmental factors sudangrass, pearl millet and the close will limit the regrowth poten­ such as time of day, humidity, sorghum-sudangrass hybrids should tial of these forages, resulting in weather forecast and other factors. always be conditioned to increase thin stands. Leave at least 2 to the drying rate. In these forages, 3 inches of stubble when harvesting Drying agents. Drying agents water can remain trapped in these forages. such as sodium and potassium uncrushed stems long after the carbonate that can be sprayed on Some types of forages require leaves are dry enough to bale. In leafy forages are available. These much higher (6- to 8-inch) mowing contrast, conditioning rollers should products can reduce drying time, but heights. These forages include be opened to a wide gap or dis ­ the cost must be weighed against the sudangrass, pearl millet, sorghum­ engaged when harvest ing cereal likelihood of rainfall events. Drying grains with filling grain heads. By sudangrass hybrids, johnsongrass agents do not usually enhance the the soft-dough stage of growth, most and eastern gamagrass. For annuals drying time for cool-season grasses. of the nutritive value in these such as sudangrass, pearl millet and This may occur because the leaf forages is associated with the grain the sorghum-sudangrass hybrids, sheath prevents the drying agent head and not the stover. Therefore, clipping at shorter heights will slow from contacting the stem directly. the regrowth response after harvest. an improperly adjusted conditioner Mechanical manipulation. that thrashes grain will greatly In addition, these forages are noto­ rious for accumulating nitrates when Unlike most grasses, alfalfa and reduce the overall quality of the other legumes should not be raked hay or silage. growing conditions are stressful. Typically, nitrates are most likely to or tedded when the moisture content Cutting height. The various accumulate in the highest concentra­ falls below 35 to 40 percent mechanisms used by forages to tions in the lower portions of the (Table 4). In addition, these convert carbon dioxide into sugars stem. Maintaining a mowing height processes should be as gentle as and then store these energy com ­ of 8 inches or higher will encourage possible. The ground speed of the pounds to support regrowth after aggressive regrowth and provide rake and the general aggressiveness harvest have an important effect on some help in reducing the risk of of the raking mechanism should be forage management. Generally, nitrate poisoning. Eastern gamagrass reduced if leaves are obviously plants that store their growth is a warm-season perennial that is being shattered. Various mechanical reserves underground, such as extremely sensitive to close mowing processes that are improperly alfalfa, are less affected by cutting heights. It is absolutely essential to managed will greatly encourage leaf height and can be mowed very leave at least 6 to 8 inches of and DM losses in alfalfa and most short. In the case of alfalfa, cutting stubble, measured from the top of other legume hays (Table 4). heights can be 1 to 2 inches if the the crown, when mowing this forage Grasses and legumes, however, stand is generally healthy. In addi­ as a hay or silage crop. are fundamentally different. In tion, plants that store growth grasses, both the leaf and stem have Swath width. If forages are to reserves in stolons or “runners” that some structural function; therefore, be baled as hay, they should be lay on the soil surface (bermuda­ they are more similar in quality than mowed in wide swaths to encourage grass and white or ladino clovers) in legumes. In alfalfa, the function drying, at about 75 percent of the typically are tolerant of close of the stem is almost entirely struc­ baler width. Dense, narrow swaths mowing or grazing heights. Close tural, while the leaf is extremely will not dry as fast; however, this cutting of bermudagrass stands can fragile and contains most of the can be used to slow wilting when be used to decrease the persistence metabolic machinery of the plant. alfalfa or other crops, such as cereal of other undesirable plants to a Therefore, legume leaves are grains, are being harvested as silage certain extent. Many cool-season extremely high in nutritive value, and maintaining moisture in the perennial forages, including smooth relative to the stem tissues that are windrow is essential. As the yields bromegrass, orchardgrass and tall heavily lignified. In addition, the increase, the drying time required fescue, are more sensitive to quality of legume leaves changes before baling increases, regardless extremely close mowing heights. only marginally with maturity, but of swath width. Once hay is dry at These types of plants store their the quality of the stems will about 40 percent of DM, swaths can growth reserves in the stem bases decrease rapidly. In contrast, the be raked into windrows. Depending and require a certain amount of leaf digestibility of both leaves and on the crop, the exact raking time is area for regrowth. Removal of these stems decreases markedly with

10 Table 4. Alfalfa losses of DM and leaves during various haymaking and should not be viewed as a operations.1 technique that allows producers to % of % of bale excessively wet hay. Operation DM Lost Leaves Lost Conservation of plant Mowing 1 2 sugars. Plant sugars and other Mowing/conditioning: nonstructural carbohydrates are reciprocating mower, fluted rollers 2 3 highly diges tible; therefore, it is disc mower, fluted rollers 3 4 disc mower, flail conditioner 4 5 desirable to conserve these com ­ pounds during the haying process. Raking: at 70% moisture 2 2 Generally, perennial cool-season at 60% moisture 2 3 grasses have higher concentrations at 50% moisture 3 5 of nonstructural carbohydrates than at 33% moisture 7 12 either legumes or perennial warm- at 20% moisture 12 21 season grasses. Lush, immature Tedding: at 70% moisture 1 2 forages usually have relatively low at 60% moisture 1 3 concentrations of sugars. Forages at 50% moisture 3 5 mowed late in the afternoon will at 33% moisture 6 12 have higher concentrations of plant at 20% moisture 11 21 sugars than those harvested in Baling, pickup + chamber the morning; how ever, specific at 25% moisture2 3 4 at 20% moisture 4 6 attempts to harvest sugars by post­ at 12% moisture 6 8 poning mowing until late afternoon Baling at 18% moisture: are not necessarily advised except conventional rectangular baler with ejector 5 8 under arid drying conditions. round baler, variable chamber 6 10 round baler, fixed chamber 13 21 Nonstructural carbohydrates can be lost at several points during the 1 Source: R. E. Pitt. Silage and Hay Preservation. Northeast Regional Agric. Engr. Service. NRAES-5. Ithaca, NY. Data compiled from Kjelgaard [Trans. ASAE 22:464­ haying process, and a large per ­ 469 (1979)]; Hundtoft [Extension Bulletin 364, Cornell University (1965)]; and Rotz centage of these compounds are lost [DAFOSYM: The Dairy Forage System Model. USDA- ARS (1989)]. even when weather conditions are 2 Requires a preservative for safe storage. ideal. During the wilting process, sugars are consumed (as an energy source) as plant cells try to continue maturity in most grasses. Therefore, be very short. Generally, alfalfa hay functioning while the forage dries in it is necessary to conserve the needs to be wilted to 20 percent the swath. This respiratory activity extremely fragile leaves of legumes moisture to prevent excessive spon­ within plant cells is usually a minor during the haymaking process to taneous heating during storage; cause of DM loss after the plant maximize the nutritive value of however, significant leaf loss will the hay. occur with any baler when the mois­ reaches about 40 per cent moisture. ture content falls below this level. Air temperature also affects respira­ Balers. Using the proper baler Preservatives are occasionally tion because enzymatic activity is is important when producing quality sprayed onto the forage at the baler increased at higher temperatures; alfalfa hay. Generally, large round in an effort to bale hay that is however, this relationship is con ­ balers should be avoided. Some slightly wet, thereby conserving founded because higher tempera­ studies have reported losses of leaves. The most common of these tures also increase drying rate. It 13 percent of DM and 21 percent of preservatives is propionic acid, is undesirable for mowed hay to alfalfa leaves with these balers. which can be effective in limiting remain in the swath for prolonged Conventional rectangular balers or the undesirable effects of respiration periods under poor drying condi­ large square balers that use a and spontaneous heating. These tions (high humidity, fog, etc.), even plunger system do a much better job products generally permit the safe in the absence of rain. This will of conserving leaves. The window storage of hays that are marginally always result in poor recovery of of opportunity for baling alfalfa can wet (less than 30 percent moisture) nonstructural carbohydrates.

11 Table 5. Effects of rainfall and forage type on nutritive characteristics of levels in the forage. The effects of three legumes. Analysis includes shattered leaf fragments.1 rainfall on three legumes are shown Crude Forage in Table 5. These results illustrate Treatment % Leaf Protein NDF2 ADF Lignin TNC Digestibility the effects of leaching only; ------% of DM ------­ shattered leaf fragments were Alfalfa included in the analysis. When leaf Control 56.8 15.5 32.3 25.9 5.3 12.2 71.5 shatter is also considered, quality Wet 48 hours3 53.5 18.7 34.1 27.4 5.5 10.7 71.0 depression and DM losses can be Wet 24 and 48 hours4 45.6 18.2 38.4 29.9 6.0 8.0 69.2 severe. Digestibility decreased from 72.7 to 49.3 percent and from 62.3 Red Clover Control 92.7 14.6 29.1 21.6 3.2 15.7 75.8 to 36.0 percent in response to a Wet 48 hours 97.0 16.9 32.7 24.1 4.0 12.7 72.6 2.4-inch rain event on dry alfalfa Wet 24 and 48 hours 96.8 17.5 39.9 28.9 4.8 5.2 67.0 harvested at late bud stage and first flower, respectively (Table 6). Based Birdsfoot trefoil on the few available research Control 52.9 13.7 31.0 24.6 5.9 15.2 71.3 Wet 48 hours 48.1 13.9 36.0 29.6 7.1 13.4 70.2 studies, the effects of rainfall appear Wet 24 and 48 hours 47.1 15.2 40.8 32.1 7.8 9.6 66.4 to be more severe when the forage is 1 M. Collins, Agronomy Journal 74:1041-1044 (1982). dry. Generally, the effects of rainfall 2 Abbreviations: NDF, neutral detergent fiber; ADF, acid detergent fiber; and TNC, total on drying grasses remain poorly nonstructural carbohydrates. defined; however, cool-season 3 Artificial rainfall amount was 1.0 inch at 48 hours. grasses contain large concentrations 4 Two applications of 1.0 inch of water at 24 and 48 hours. of sugars and other nonstructural carbohydrates that are water soluble Table 6. Effects of rain and plant maturity on alfalfa quality. Shattered plant matter was not included in the analysis.1 and easily leached. Therefore, concentrations of less digestible 2 3 Maturity No Rain Rain Rain on Dry Hay structural plant fiber will likely ------% of DVM ------increase after rainfall events. Leaf Crude protein shatter that occurs as a result of Late bud 26.3 24.6 23.1 rainfall is usually less of a problem First flower 18.1 13.9 15.6 Digestibility with grasses than with legumes. Late bud 72.7 57.2 49.3 First flower 62.3 39.2 36.0 TNC 4 Spontaneous Heating Late bud 4.65 2.00 1.21 First flower 4.46 1.89 0.98 Introduction. The negative NDF consequences of baling hay before it Late bud 32.4 45.4 54.8 First flower 42.2 64.1 69.8 is adequately dried are widely ADF known to producers. Frequently, Late bud 27.5 38.5 46.2 these problems are created by First flower 36.4 53.0 58.4 uncooperative weather conditions Lignin Late bud 5.5 9.7 11.5 that prevent forages from drying First flower 9.1 13.8 16.6 (rapidly) to moisture contents that 1 M. Collins, Agronomy Journal 75:523-527 (1983). allow safe and stable storage of 2 1.6 inches of rain during curing harvested forages. Negative con­ 3 2.4 inches of rain on dry hay sequences associated with baling 4 Abbreviations: TNC, total nonstructural carbohydrates; NDF, neutral detergent fiber; hay before it is adequately dried and ADF, acid detergent fiber. include molding, spontaneous heating and undesirable changes in Rain damage. Research legumes (Tables 5 and 6). Generally, forage nutritive value. trials that describe the effects of rain will leach soluble nutrients rain on drying forage crops are (primarily sugars) from hay, result­ Mechanisms. Spontaneous quite limited. Most of this work has ing in DM loss, increased concentra­ heating is the most obvious result of been confined to alfalfa and other tions of fiber and decreased energy plant and microbial respiration

12 within the hay bale. Respiration is of respiration by storage micro ­ heat developed per unit of DM is the process in which plant cells and organisms. The hay bales made at independent of bale density. This different microorganisms consume 30 percent moisture maintained a suggests that bale density increases sugars in the presence of oxygen to higher internal bale temperature than spontaneous heating simply because yield carbon dioxide, water the drier hay (20 percent moisture) more hay is packaged within the and heat: for about 25 days. Similar trends bale. Larger and denser packages can be observed for characteristics also tend to have higher internal Plant Sugars + Oxygen→→→→→→ of spontaneous heating in bermuda­ bale temperatures because the Carbon Dioxide + Water + Heat grass hays (Figure 3). heat produced is more difficult to dissipate. This process causes the internal Bale size and density also have temperature of any hay bale to a positive effect on heating in hay Measuring spontaneous increase and ultimately lowers the packages. However, the amount of heating. Under research conditions, energy content and digestibility of the forage. Spontaneous heating Figure 2. Typical patterns of spontaneous heating in conventional actu ally helps to dry the hay rectangular bales of alfalfa hay packaged at 30 and 20% moisture and because it encourages the evapora ­ stored in small stacks in Manhattan, KS. Source: W. K. Coblentz. tion of water. Many factors con ­ tribute to the extent of heating. These include:

• Moisture content at baling • Bale type • Bale density • Environmental factors, such as relative humidity, ambient temperature and air movement • Storage site • Use of preservatives

Usually the extent of heating that occurs in any hay bale is a good indicator of the undesirable changes in nutritive value that may be observed after storage. Figure 3. Typical patterns of spontaneous heating in conventional rectangular bales of bermudagrass hay packaged at 31, 27 and 17% Figure 2 shows the typical moisture and stored in small stacks in Fayetteville, AR. patterns of spontaneous heating that Source: W. K. Coblentz. occur over time in storage for conventional rectangular alfalfa hay bales made at 30 and 20 percent moisture. Beginning immediately after baling, the internal bale temperature rises due to respiration of both plant cells and microbes associated with the plant in the field. This heating usually lasts less than five days. Following a short period in which internal bale temperatures nor mally decrease (at 4 to 5 days post-baling), a pro longed period of heating begins that can last several weeks. This heating is the result

13 spontaneous heating usually is not baled in Fayetteville (Figure 5). In moisture content at baling, and measured simply as internal bale that study, about 43 HDD were this relationship is linear (HDD temperature. The concept of heating accumulated for each increase of increases at a constant rate with degree days (HDD) is often used as one percentage unit in the moisture bale moisture). a single index that incorporates both content at baling. Regardless of the These studies were all the magnitude and duration of forage type, the level of heating that conducted with conventional small heating during the entire storage occurs is primarily driven by rectangular bales. While it is period. Heating degree days usually are calculated by subtracting 86°F Figure 4. Relationship between heating degree days > 86°F (HDD) (30°C) from the daily internal bale accumulated in conventional rectangular bales of alfalfa hay (■)and temperature; these differences are the concentration of moisture in the bale at packaging. Heating degree then summed over all days in days can be interpreted as a single number that represents both the magnitude and duration of heating within the bale. storage. An example of how HDD Source: W. K. Coblentz. are calculated is summarized below:

Bale Degrees Day Temperature, °F > 86°F 1 108 22 (108-86) 2 104 18 (104-86) 3 115 29 (115-86) 3-day total 69

This concept is often used to limit effects of ambient air tempera­ ture and because negative changes in forage nutritive value are most noticeable when internal bale temperatures exceed 86°F. Heating degree days can be viewed as a relative measure of the heat produced within each bale. Heating degree days totaling 150 or less are Figure 5. Relationship between heating degree days > 86°F (HDD) accumulated in conventional rectangular bales of bermudagrass hay (●) indicative of relatively minimal and the concentration of moisture in the bale at packaging. Heating spontaneous heating; conversely, degree days can be interpreted as a single number that represents both totals in excess of 800 HDD are the magnitude and duration of heating within the bale. indicative of hay that was baled Source: W. K. Coblentz. excessively wet, probably at about 30 percent moisture.

Of all the factors that affect spontaneous heating, moisture content at the time of baling is the most impor tant. Figure 4 summarizes several alfalfa hay experiments conducted in Kansas. The relationship between moisture content and HDD is quite close (r = 0.902). A one per centage unit increase in the moisture content of the forage at baling results in 56 HDD. A similar relationship was observed for bermudagrass hay

14 generally assumed that similar not occur in the center of the stack measured during storage. In the relationships between moisture because lower concentrations of alfalfa hay, some DM loss (about content and spontaneous heating oxygen may limit temperature 2 percent of the initial DM) exist in large round bales, there is increases and make combustion less occurred even when no HDD were limited documented research to likely. It is more commonplace to measured during the storage period. support this. Typically, the recom­ observe spontaneous combustion mended moisture content at baling near the outside of the stack where This occurred because some for larger round hay bales is lower concentrations of oxygen are higher. respiration takes place when internal than is necessary for con ventional bale temperatures are below 86°F. rectangular bales. A good rule of DM Recovery in Heated Hays For bermudagrass hay, losses of DM thumb for maintaining acceptable also are related closely to the maxi ­ storage in conventional rectangular Dry matter is lost whenever mum internal bale temperature hay packages is to bale hay at heating occurs in hay bales. Dry recorded during the storage period 20 percent moisture or less; how­ matter losses occur in virtually all (Figure 7). These data indicate that ever, this guideline is often reduced hay packages, but these losses are bermudagrass hay packaged in to 16 to 18 percent moisture for relatively minor without evidence of conventional rectangular bales will larger hay packages. heating. Most of the DM that is lost lose 1.3 percent of the initial DM in during hay storage is nonstructural the bale for every increase of 10°F A recent study conducted with carbohydrate (plant sugars) that are in the maximum internal bale mixtures of orchardgrass and alfalfa respired to carbon dioxide, water temperature. It is important to note at the University of Tennessee and heat. Losses of DM will that Figures 6 and 7 both display (Montgomery et al., 1986; J. Dairy increase with increased moisture data that was collected from conven­ Sci. 69:1847-1853) measured the content at baling and subsequent tional rectangular bales. Although it internal bale temperature of spontaneous heating. Figure 6 is assumed that these trends are 1,373-pound round bales made at summarizes DM losses in con ­ similar in large round bales, these 24 percent moisture during a 96-day ventional rectangular alfalfa and relationships cannot be applied storage period. These results were bermuda grass hay bales over several directly to larger hay packages. compared with those of 25-bale experiments. For both hay types, Generally, DM losses associated stacks of the same material baled as about 1 percent of the initial DM in with spontaneous heating are greater con ventional rectangular bales. the bale is lost for every 100 HDD in larger hay packages. Maximum internal bale temperatures for both bale types occurred at about the same time (11 to 12 days of Figure 6. Relationship between dry matter recovery after storage and storage); however, the peak internal heating degree days > 86°F (HDD) for conventional rectangular bales of alfalfa (■) and bermudagrass (●) hays made in Manhattan, KS, and bale temperature for the round bales Fayetteville, AR, respectively. was about 190°F com pared to only Source: W. K. Coblentz. 104°F for the conventional rectan­ gular bales. Internal bale tempera­ tures in round bales can reach levels comparable to those in the University of Tennessee study through the respi­ ratory processes of plant cells and microorganisms. However, higher temperatures are caused by oxidative chemical reactions that may occur as long as 30 days after baling. Clearly, large round bales are more prone to heat spontaneously and have a higher risk of combustion. Sponta neous combustion is thought to occur when internal bale temperatures reach about 340°F. Normally, this does

15 Figure 7. Relationship between DM recovery after storage and the res piratory processes in hay bales is maximum internal bale temperature for conventional rectangular bales of nonstructural carbo hydrates, or plant bermudagrass hay (●) made in Fayetteville, AR, in 1998. sugars. When hay bales heat sponta­ Source: W. K. Coblentz. neously, concentrations of NDF, ADF and other fiber components increase. This is not because more plant fiber is actually constructed. The mechanism is indirect; as more plant sugars and other cell solubles are consumed during microbial respi­ ration, the concentrations of the fiber components increase. Recent research with alfalfa hay baled at 30 percent moisture showed that concentrations of NDF increased rapidly between 0 and 12 days of storage (the period of active respiration and high internal bale temperatures), but were rela­ tively stable after 12 days (Figure 8). Higher concentrations of NDF as hay packaged at 20 percent mois ­ were reached in the hay baled at Nutritional Characteristics ture. This is due to the greater heat ­ 30 percent moisture because of ing that occurs in hay made at the increased spontaneous heating of Heated Hays 30 percent moisture. The time inter ­ that occurred in this hay. Similar relation ships have been observed Plant sugars. During the val when concentrations of non ­ in bermudagrass hays made in spontaneous heating process, sugars structural carbo hydrates fall most Fayette ville, Arkansas, during the are oxidized. This results in rapidly (0 to 12 days) coincides with summers of 1998 and 1999. increased concentrations of more the period of most intense heating in hay bales (Figure 2). During this stable plant components such as Total digestible nutrients period of intense spontaneous heat ­ structural fiber (NDF, ADF) and, to (TDN). The concentration of TDN ing, plant sugars in all hays are oxi ­ a lesser extent, protein. This results (or energy) in a forage is often pre­ dized as a fuel source for rapidly in a decrease in the energy content dicted from equations on the basis of proliferating microorganisms in the and digestibility of the forage. As concentrations of fiber (ADF and/or hay. Ultimately, this negatively a standing crop, the concentrations NDF). As the concentrations of NDF affects the nutritive value of the hay of nonstructural carbohydrates in and ADF increase, TDN usually because sugars are among the most alfalfa can exceed 20 percent of the declines. Any process (such as spon­ digestible components of any forage. total plant DM. Even when alfalfa taneous heating or rain damage) that is wilted under excellent drying Fiber components. Forage affects the concentrations of fiber conditions, the concentrations of fiber components, such as NDF, components in a forage will often non structural carbohydrates can fall ADF, crude fiber, lignin and ash, have a noticeable effect on the TDN to less than 8 percent of DM by remain relatively stable during bale content. In Arkansas, the TDN con­ the time the forage is baled. This storage. These com ponents essen­ tent of warm-season grasses is pre­ occurs as a result of unavoidable tially comprise the cell wall or struc­ dicted from an equation that utilizes plant respira tion during the wilting tural portion of forages and are the the concentrations of NDF, ADF and pro cess. During storage, alfalfa con ­ least digestible parts of the plant. CP. Figure 9 illus trates the relation­ tinues to lose nonstructural carbo ­ The NDF con centration of forage ship between estimated TDN and the hydrates to microbial respiration. plants is equated with the concentra­ maximum internal bale temperature Hay packaged at 30 percent mois­ tion of cell wall within the forage; during storage for bermuda hay ture has about half the concentration low NDF concentrations normally baled in conventional packages. of nonstructural carbohydrates at indicate high nutritive value. The TDN content declined by the end of a 60-day storage period The primary energy source for the 1.1 percentage units for every

16 increase of 10°F in the maximum Figure 8. Relationship between the concentration of NDF and storage internal bale temperature. time for alfalfa hay packaged in conventional rectangular bales at 30 (—) and 20 (---) percent moisture in Manhattan, KS. Source: W. K. Coblentz. Digestibility. Most measures of forage nutritive value are affected negatively by spontaneous heating. Digestibility is no exception. As nonstructural carbo hydrates and other highly digestible compounds within the forage plant are lost to respiration, concentrations of less-digestible plant components (particularly fiber components) increase noticeably. This often decreases the digestibility of the forage. For bermudagrass hay made in Fayetteville in 1998 (Figure 10), the effects of heating on forage digestibility appeared to be minimal when the internal bale temperature did not exceed 120°F. However, as Figure 9. Relationship between energy content (TDN) and the maximum the internal bale temperature internal bale temperature for conventional rectangular bales of bermuda­ increased above 120°F, forage grass hay (●) made at Fayetteville, AR, in 1998. Source: W. K. Coblentz. digestibility decreased dramatically. In this study, forage digestibility dropped by about 14 percentage units when the maximum internal bale temperature exceeded 140°F. Crude Protein. Concentrations of CP are not stable during bale storage. Generally, the observed changes in concentrations of CP are somewhat dependent on time since baling. In the short term (< 60 days), CP content may actu­ ally increase in a similar manner to that described for fiber compo­ nents; however, CP can also be used as a fuel for microbial respiration, particularly after supplies of plant storage is to decrease CP content. noticeably different concentrations sugars are exhausted. Table 7 Concentrations of CP are often of CP that are not associated with shows the effects of spontaneous reduced by 0.25 percentage units laboratory errors. heating on the CP concentration of per month of long-term storage bermudagrass hay bales sampled due to volatilization of ammonia Heat-damaged protein. Heat after 60 days in storage. Although and other nitrogenous compounds; can damage forage proteins. Unlike spontaneous heat ing has positive however, this loss is unlikely to fiber components, con centrations of short-term effects on concentrations continue indefinitely. Therefore, heat-damaged protein increase by of CP, this should not be viewed as the concentrations of CP can direct mechanisms during bale a justification for baling hay before increase in response to spontaneous storage. This causes forage protein it is dry. heating during short-term storage to become indigestible when con ­ (< 2 months) but decrease thereafter. sumed by ruminants. Moisture The long-term effect of The same forage sampled at dif­ content, the magnitude and duration spontaneous heating during bale ferent points in time can have of spontaneous heating and forage

17 Figure 10. Relationship between digestibility and the maximum internal The concentrations of heat-damaged bale temperature for conventional rectangular bales of bermudagrass protein increase at a rate of about ● hay ( ) made at Fayetteville, AR, in 1998. Source: W. K. Coblentz. 0.4 percentage units per 100 HDD in alfalfa hay, which is about half the rate observed for bermudagrass hay (0.8 percentage units per 100 HDD). Grass hays are typically more susceptible to this type of damage than alfalfa or other legumes. Ruminant nutritionists usually consider alfalfa hay to be seriously heat damaged when concentrations of heat-damaged protein exceed 10 percent of all forage protein.

Other management factors, such as large round balers or higher- density hay packages, will increase the possibility of spontaneous Table 7. Concentrations of crude protein (CP) for bermudagrass hay bales made from the same field and sampled after 60 days of storage heating and the probability of heat at Fayetteville, AR, during 1998.1 damage to forage protein. Even Initial Moisture Maximum though concentrations of heat- Content HDD2 Temperature CP damaged protein increase by % °F% mechanisms different than those 31.3 1,055 144 15.3 for NDF and ADF, most increases 33.6 1,057 142 15.7 in concentrations of heat-damaged 27.7 1,100 140 15.0 protein still occur early in the 29.8 990 138 15.0 storage period (< 20 days). 26.6 925 135 15.8 22.9 763 124 14.2 Ruminal protein 21.1 621 111 14.0 20.5 542 109 15.4 digestibility. Considerable 16.9 445 101 14.2 research effort has been devoted to 18.7 484 108 14.5 assessing the ruminal digestibility of 1 Source: W. K. Coblentz forage protein. This is the proportion 2 HDD = heating degree days > 86°F. of forage protein that is broken down or digested in the rumen. type all affect the amount of heat spontaneous heating exists for both Forage protein that escapes the damage that may occur to forage alfalfa and bermudagrass hay. All rumen intact is often referred to as proteins. Moisture plays a critical forages have some indigestible “bypass protein.” Much of this role in this process in two ways. protein that is inherently unavailable research effort has been centered First, it has a catalytic effect. This is to livestock. This fraction is small in around efforts to improve dairy the reason proteins in silages are most standing forages or unheated production. High-quality forages, more susceptible to heat damage hays. Concentrations of indigestible such as alfalfa, frequently have high than proteins in forages conserved protein in unheated alfalfa can range concentrations of CP, but this protein as hay. Secondly, the moisture between 3 and 6 percent of all the is rapidly degraded in the rumen and within the hay at baling stimulates protein in the forage. Typically, the inefficiently utilized by dairy cows spontaneous heating, which subse­ indigestible protein in unheated and other livestock. Spontaneous quently increases the probability of warm-season grasses represents a heating limits both the rate and heat damage. higher percentage of the total amount of forage protein digested in A positive linear relationship forage protein. It can be higher than the rumen. While this may provide between heat-damaged protein and 20 percent in dormant forages. some benefit with respect to nitrogen

18 retention and utilization, it should not weathering hay bales than smaller, It should also be noted that larger be viewed as a justification for inten­ more frequent rainfall events. hay packages have lower percent­ tionally allowing forages to heat in Losses are generally reduced in arid ages of weathered forage than the bale. climates and in northern climates smaller hay packages; however, with severe winters because the larger and more expensive tractors Digestion of protein in the environmental conditions are less are often required to handle larger rumen is naturally less rapid for favorable for microbial activity. hay packages. warm-season grasses, such as Within any specific environment, bermudagrass. This natural resist­ DM losses are nearly proportional Limiting hay/soil contact. It ance to ruminal digestion is associ­ to storage time. is easy to overlook the importance ated with the differences in plant of the bottom of the bale when anatomy between warm-and cool- Crop factors. Some crops discussing weathering losses. Some season plants. Unlike alfalfa and are naturally more resistant to reports suggest that approximately other legumes, it is not necessarily weather ing. Generally, fine-stemmed, 50 percent of the storage losses in desirable to slow the rate of ruminal leafy, weed-free crops, such as hays stored outside occur at the digestion of protein in warm-season bermudagrass or tall fescue, form an hay/soil interface. This occurs forages. However, spontaneous excellent thatch that sheds water. because the dry hay acts as a wick, heating will have the same effect Other crops with large, coarse stems drawing moisture from the soil. on warm-season hays that it does do a poorer job of shedding water. Depending on the site, air move­ on alfalfa. Good examples of these types of ment may not be as great around forages include sudangrass, pearl the hay/soil interface as it is around millet, sorghum-sudangrass hybrids the top of the bale. These factors Weathering Effects and johnsongrass. Water can easily combine to produce a moist environ­ penetrate bales made from these Introduction. Spontaneous ment at the bottom of the bale that forages and accelerate the weathering heating is not the only factor that is more favorable to microbial process. Hays with coarse-stemmed activity. There are many ways to can affect the nutritional value of weeds also do a poor job of shedding stored hay. Over the last two limit con tact between hay and soil. water and weather quicker than Wooden pallets, railroad ties, pipe, decades, large round bales generally weed-free hays. have replaced small rectangular tires and telephone poles can all be bales as the preferred type of hay Bale size and density. used to support hay bales and pre ­ package largely because of the Dense, uniform hay packages will vent contact with the soil. Ideally, reduced requirement for labor. Many limit weathering losses compared to any base should allow some air of these round bales are stored out­ loosely baled hay packages. Bales movement under the bales to side without any protection against that have 10 pounds of hay per facilitate drying. Crushed rock can the weather. The weathering of the cubic foot in the outer layer will be used as a base to limit contact outside layer can have a major help to reduce penetration by rain. with the soil. Crushed rock that is impact on the nutritional characteris­ The density of the inner core is less 1 to 3 inches in diameter and piled tics and DM recovery of hay. It also important than the outer layer. Bale 4 to 8 inches deep should not trap may result in greater refusal and density can be increased by raking water but should channel it away reduced intake by livestock. hay swaths into smaller windrows from the bales. Crushed rock also and reducing the ground speed of has the added advantage of lasting Weathering is partially a physical the baling tractor. These practices many seasons and repair of the process caused by the leaching of will result in more layers per bale storage site is simple. If bales must soluble forage nutrients during and a greater overall bale density. be placed directly on the ground, rainfall. Since most soluble com­ Unfortunately, this also will increase select a well-drained site with a pounds in forages are highly leaf shatter in legume hays. While sandy soil type. digestible, it is desirable to limit baling dense hay packages will help these losses during storage. A to limit weathering effects, it also Any site selected for the storage second type of weathering is the will increase the likelihood of of hay bales should be in a sunny, result of microbial activity that spontaneous heating. Therefore, breezy, well-drained area, possibly increases under moist, warm condi­ every effort should be made to near the top of a slope. Bales should tions. Infrequent heavy rains are reduce the forage moisture content be oriented in rows that run up and likely to have less impact on to 18 percent or less before baling. down the sloping area, preferably

19 Table 8. Depth and volume of weathered layer and DM losses from tall fescue round bales stored inside and outside with different binding materials.1 Weathered Layer as DM Loss With All Dept of Percentage of Weathered Layer Treatment Weathered Layer Bale Volume Actual DM Loss Considered Lost2 inches ------% ------­ Plastic mesh wrap/ground 2.1 13.6 10.6 23.3 Solid plastic wrap/ground 0.6 3.9 3.6 7.8 Sisal twine/ground 4.4 26.8 18.2 34.1 Sisal twine/inside 0 0 5.7 5.7 1 Collins et al., 1995; Journal of Production Agriculture 8:507-513. 2 Entire weathered layer considered to be unrecovered DM. with a southern exposure. Rows of and stored outside and 4) bales that pro ducers are losing far more bales oriented perpendicular to a tied in the same manner as #3 but DM and nutritive value than they sloping surface will trap moisture stored inside. Bales stored outside may realize. following rainfall. Rows of bales were positioned in a north-south should be positioned with the flat orientation with 3 feet between Effects of storage method ends of each bale butted together. adjacent bales. The storage site on nutritive value. In the The rounded sides of adjacent rows had a 5 to 7 per cent slope. Bales University of Kentucky study, should not touch each other. There stored inside were placed in a well- storage treatment had a large effect should be about 3 feet between adja­ ventilated structure that provided on the nutritive value of the exterior cent rows to insure good air circula­ protection from the weather. All weathered layer after the one-year tion and penetration of sunlight. bales were stored for one year storage period (Figures 11 and 12). Bales should not be stored under before sampling and analysis. Concentrations of CP (Figure 11) trees or ever rest in standing water. Twine-tied bales stored inside and were approximately two percentage It is best to select a site that has no solid plastic-wrapped bales lost units higher in the exterior weath­ objects that will attract lightening, relatively small amounts of DM ered layer of bales wrapped with and the posting of no smoking signs (< 6 percent). This amount of DM plastic mesh or sisal twine and may remind others that a hay crop loss is comparable to that observed stored on the ground than in the represents a serious investment of in several other studies for round unweathered interior of the same time and money. It is also a good bales stored inside. Plastic mesh- bales. For bales wrapped in solid idea to have multiple storage sites. wrapped and twine-tied bales stored plastic and stored on the ground, This will reduce the risk of a fire outside lost considerably more concentrations of CP were a little destroying an entire hay supply at (> 10 percent) of the total DM; more than half a percentage unit one time. however, the twine-tied treatment higher in the exterior weathered appeared to be the least desirable layer than in the unweathered Effects of storage method (18.2 percent DM loss). It is impor­ interior of the same bales. There on losses of DM. Several studies tant to note that a relatively shallow was essentially no difference have attempted to quantify storage (4.4 inches) weathered layer between the weathered exterior losses of DM in large round bales. accounted for 26.8 percent of the and the unweathered interior for Table 8 sum marizes a recent study total bale volume for twine-tied tall fescue hay bales stored inside. with tall fescue conducted at the bales stored outside. Bales in the Elevated concentrations of CP in University of Kentucky. Four Kentucky trial measured 4 by the weathered layer also can be combinations of wrapping and 4.5 feet. Generally, the weathered observed in alfalfa hay (Table 9). storage methods were evaluated. layer in smaller bales will account These observations indicate that These included 1) bales wrapped for a larger portion of the total CP is more stable during the with two layers of plastic mesh and bale volume than a weathered weathering process than other stored outside, 2) bales wrapped layer of comparable depth in larger plant components (especially with two layers of solid, 1.5-mil, bales. However, even relatively sugars), and that CP increases self-adhesive wrap and stored shallow weathered layers can over time in the weathered layer outside, 3) bales tied with sisal account for very large portions of because less stable plant compo­ twine spaced at 4-inch intervals the total bale volume. This suggests nents that are usually highly

20 digestible are lost by leaching, Figure 11. Concentrations of crude protein (CP) in weathered and oxidation or other processes. unweathered layers of tall fescue hay packaged in large round bales in Kentucky. Source: Collins et al., 1995; Journal of Production Generally, the effects of Agriculture 8:507-513. weathering can be expected to increase the concentrations of fiber components (NDF, ADF, cellulose, hemicellulose and lignin) and reduce digestibility. The effects of weather ing on the digestibility of tall fescue hay in the University of Kentucky study were quite substan­ tial (Figure 12). The digestibility of the weathered layer for bales tied with plastic mesh or sisal twine and stored outside on the ground was reduced by about 22 and 18 percentage units, respectively, relative to the digesti bility of the unweathered interior core of these same bales. For bales wrapped in solid plastic and stored outside on the ground, the digesti bility of the weathered layer was reduced by Figure 12. Digestibility of weathered and unweathered layers of tall about 6 percentage units relative to fescue hay packaged in large round bales in Kentucky. Source: Collins the unweathered core. There was et al., 1995; Journal of Production Agriculture 8:507-513. essentially no change for bales stored inside. In a separate study, the digestibility of the weathered exterior layer for large round bales of alfalfa was 14.5 percentage units lower than the unweathered interior core (Table 9). These findings indicate that the nutritive value of the weathered exterior layer of hays stored outside can be substantially poorer than the unweathered interior core of the bale. The effects of weathering on the bale as a whole will depend on the magnitude of changes in nutri­ tive value between the unweathered and weathered portions, and the depth of the weathered layer. Simple management techniques should be Table 9. Forage quality of the interior and exterior portions of alfalfa used to limit weathering in hays round bales stored outside.1 stored outside. In general, it is Portion of Bale CP ADF Digestibility much easier to justify expenditures, ------% of DM ------such as storage barns or sheds, to Unweathered 18.9 38.6 61.4 protect baled hays when the initial Weathered 19.4 45.8 46.9 quality of the forage is high. 1 Anderson et al., Transactions of the American Society of Agricultural Engineers 24:841-842 (1981).

21 this point. Bermudagrass from a levels in the forage. If possible, Cautions for Fertilization high soil-test phosphorus site was forages should be tested before fer tilized with varying rates (0, 50, mowing, grazing or feeding, espe­ Depletion of soil-test 100, 150, 200, 250, 300 lb N/acre) cially if the climate conditions are potassium. Some cautions are of ammonium nitrate (34-0-0) and stressful for plant growth. Consult advised with respect to fertilization clipped on three dates during 2000. with your county extension agent strategies for hay production. No other fertilizer was applied. The about submitting samples. Although hay production is last waste application on this site commonly driven by nitrogen was in 1999. In May 2000, soil tests Nitrate poisoning can affect fertilization from commercial sources indicated that potassium levels were several species of livestock, including or animal waste, it is important to considerably in excess of soil test cattle, sheep and goats. It usually remember that other nutrients are recommendations, which is not occurs after prolonged periods of removed from the soil in addition to unusual for sites with long histories cloudy, overcast days, and drought. nitrogen. Placing fields with high of animal waste application. How ­ Application of 2,4-D, plant diseases levels of soil-test phosphorus in ever, after one year of production and soil nutrient imbalances may also continuous hay or silage production (May 2001), levels of soil test cause these plants to accumulate is the most commonly suggested potassium had fallen well below nitrates. Nitrate toxicity typically method for reducing soil-test recom mended levels, and supple­ occurs in cattle on a low plane of phosphorus. This hay or silage should mental fertilization was required. nutrition (low quality for ages, not then be fed on other sites that are low This was true at all levels of nitro ­ enough energy). Hungry, stressed in soil-test phosphorus. While this gen fertili zation. This response is cattle will usually consume more hay method is effective in reducing the much more rapid than is normally and become exposed to high levels of available phosphorus loads in the observed in attempts to “mine” nitrates over a short period of time. soil, it will also reduce levels of phosphorus from these sites. Soils Nitrate itself is not especially potassium. This is of critical impor­ should be tested regularly to main­ toxic to cattle. It is normally con­ tance and must be addressed with tain accept able levels of potassium verted to ammonia in the rumen potassium from commercial sources. in bermudagrass hay fields. and then incorporated by bacteria Bermudagrass has a critical need Nitrates. Certain forage crops into microbial protein. Nitrate for potassium. It is particularly (sorghum-sudangrass hybrids, poisoning is caused by the accumu­ important with respect to winter sudangrasses, johnsongrass and lation of nitrite, an intermediate hardiness. Bermudagrass stands that others) are known to accumulate com pound in this process. Nitrite are managed with continual fertiliza­ nitrates, particularly under stressful absorbed in the blood affects tion with nitrogen but without any growing conditions. These crops oxygen-carrying capacity and attention to potassium levels in the should be fertilized conservatively can result in asphyxi ation. There soil are prime candidates for with nitrogen fertilizer sources. Split may be no clinical signs other than winterkill and other problems. applications are probably preferably sudden death. If exposure is These problems can surface to a single, larger application, but observed early enough, one may rapidly. Table 10 illustrates this will not insure acceptable nitrate observe rapid breathing, restless­ ness, weakness, difficult breathing Table 10. Levels of soil test potassium on three dates in response to or convulsions. Treatment at this nitrogen fertilization and hay production (three harvests) on a high soil- point is often unrewarding. test phosphorus site (571 lb/acre) with a recent history of animal waste application. Source: W. K. Coblentz, J. L. Gunsaulis and M. B. Daniels. If samples are high in nitrates, the hay can often be fed safely, but it Soil Test K Soil Test K Soil Test K should be done with caution. Dilute N Fertilization Rate Yield (May 2000) (November 2000) (May 2001) the high nitrate hay with other hay lb N/acre lb/acre ------lb K/acre ------­ that is low or free of nitrates. It is 0 9,692 511 370 325 also important to make sure the cattle 50 10,310 506 375 306 are gradually exposed to high nitrate 100 11,198 442 367 293 hay. Maintaining a lower pH in the 150 11,684 480 343 318 200 12,467 524 350 316 rumen will help to limit the accumu­ 250 12,564 495 347 301 lation of the nitrite intermediates. 300 12,532 514 372 291 Feeding concentrate supplements

22 with hays known to be high in produced and their effects on There are several circumstances nitrates will lower rumen pH and livestock are discussed. that would indicate there might be a help to prevent the buildup of mycotoxin problem. Frequently, nitrites. Finally, water sources should Molds. The majority of mold only a few animals are affected be considered when manag ing high contamination occurs in the field rather than the entire herd. Out ­ nitrate hays. Ponds, shallow wells before harvest. A certain amount breaks also may appear to be and streams that collect drain age may may occur secondarily during less seasonal and often are associated accumulate high levels of nitrates. than optimal storage conditions. with a particular climatic sequence. The effects of nitrate levels in The presence of molds may not In addition, the treatment of affected forages, other feeds and water are always be obvious, and the signs animals with drugs and antibiotics additive; therefore, offering cattle observed in livestock may look often seems to be ineffective. There water from deep wells or verifying similar to those observed for many also may be evidence of fungal that other water sources are low other problems. Whether mold activity when the hay is examined. in nitrates may limit the risk of growth occurs early or late in the The level of mycotoxins can be nitrate poisoning. growing season depends on climate quite uneven throughout the forage conditions. Typically mold produc­ sample; therefore, it is important to If nitrates are known or tion will be enhanced if there is take several samples from the suspected to be high before the stress during the early growing forage has been mowed, a couple same bale. season or when there are hot days of options are available that will followed by cool nights (promoting Fescue toxicity. The subsequently reduce nitrate levels heavy condensation). Good observa­ association of the fungus in the conserved forage. Most tional skills and forage sampling Neotyphodium coenophialum with nitrates accumulate in the lower techniques will reduce the risk of tall fescue has a positive effect on part of the stem; therefore, elevating these health problems. plant persistence, but the negative the cutting height of the mower will effects of the toxins produced by reduce nitrate levels. Typically, Most molds are harmless to this fungus can have a detrimental nitrate levels are not reduced during livestock; however, their presence effect on livestock performance. the wilting or hay making processes, in feedstuffs causes decreased Some estimates report losses of up but fermentation into silage will palatability and digestive problems. to one billion dollars per year. The often cut nitrate levels by 50 per ­ The molds that are of primary amount of fungal infection can vary cent. Producers who possess the concern are those that produce toxic widely from one pasture or hay equipment necessary to make silage products known as mycotoxins. can use this technique as an effec­ field to another. These mycotoxins can affect many tive management tool when nitrate of the animal’s body systems. They Fescue toxicity in cattle levels in the forage are known to manifests itself in one of three be high. interfere with many of the digestive enzymes and result in impaired ways: fescue foot, poor performance growth and muscle formation. In (summer slump) and fat necrosis. Other Toxic Substances addition, they can have detrimental In mares, reproductive problems effects on reproductive hormones, include prolonged gestation, abor­ in Hay thereby resulting in impaired fer­ tions, birthing difficulty, thickened tility, abnormal libido and decreased placentas, lack of milk production, When most people think of milk production. Mycotoxins can large and weak foals and high hay quality, they normally are con ­ foal mortality. sidering its nutritional value for have adverse effects on the cells in livestock. Another important, and the bloodstream and can result in Fescue foot usually occurs in sometimes overlooked, considera­ anemia and increased susceptibility the late fall or winter but can occur tion is the presence of undesirable to disease. Finally, they can affect at any time of the year. The animal sub stances in hay, which will affect the respiratory and nervous systems. will often lose weight and become livestock performance and, in a These potential effects on multiple lame on the hind limbs, and there worst-case scenario, may result bodily functions make it difficult to may be gangrene of the feet, tail and in death. In this section, these pinpoint what might be wrong with tips of ears. Early signs may include undesirable substances, the con ­ the animal. This can have serious a tendency to shift weight from one ditions under which they are economic consequences. hind foot to the other and a slight

23 arching of the back. Animals will of the combined effects of the outcome, however, is usually eventually become unthrifty and toxins produced by the endophytic not successful. reluctant to move. fungus and heat stress than other The risk of blister beetle breed types. Endophyte-infected toxicosis can be reduced by certain In cattle, poor performance is forages cut for hay will have lower management techniques. Normally, the most common of the three levels of toxins if they are harvested effects. This is where most of the early in the spring. Normally, the the first harvest of alfalfa each year economic losses occur. The effects levels of toxins in these forages are is relatively safe. Blister beetles are on cattle include weight loss, reduced substantially during the attracted to flowering legumes; decreased milk production, repro­ wilting process prior to baling. there fore, harvesting at bud stage ductive problems, rough hair coat, After the initial curing process, or at first flower will reduce risks diarrhea, elevated body temperature, concentrations of toxins in stored relative to waiting until full bloom. increased respiration rate and hay are relatively stable and Some pesticides that are routinely excess salivation. Cattle with decrease at a very slow rate over applied to control alfalfa weevil and summer slump spend less time time. Ensiling these forages is potato leafhopper have labeled grazing and more time in the usually not as effective in reducing effectiveness against blister beetle. shade or in farm ponds. the concentrations of toxins Consult the label for detailed information. It would be helpful if Fat necrosis is characterized by produced by the endophyte. alfalfa and clover hays could be accumulation of hard necrotic fat in dried without conditioning rollers the abdominal or pelvic cavity. Blister beetles. Alfalfa and that kill beetles and gather them in There usually are no notable clinical other clovers may attract blister the windrow, but these crops have signs. Fat necrosis has usually been beetles. They may be found notoriously slow drying rates and associated with long-term ingestion through out the United States but are of endophyte-infected fescue that most frequently observed in the this approach is not really practical. has been heavily fertilized with mid western United States. The Ultimately, it is very difficult to nitrogen or poultry litter. One might beetles tend to swarm when the hay guarantee the absence of blister observe digestive disturbances such or nearby weeds are in bloom. beetles in alfalfa hay. Buyers are as chronic bloating, decreased Mower-conditioners that cut and well advised to view such claims rumen function, reduced feed crimp the hay with conditioning with skepticism. rollers will trap dead beetles within intake, weight loss and decreased Submitting samples for the windrow or swath. amounts of feces. Some animals toxin analysis. The care used in may become emaciated and die, These beetles produce collecting the sample of hay for others may just become poor cantharadin, which is a potent toxin laboratory analysis has a direct performers. Large masses of fat in that causes severe irritation and effect on the accuracy of the the pelvic cavity may also cause necrosis of any mucus membranes analysis. Many times this may not calving problems. that it comes in contact with. The be possible, since all of the hay has Animals with suspected fescue beetles retain their toxicity in dry already been fed. At least one quart toxicosis can be removed from the hay. All classes of animals that eat of forage should be submitted, cut infected pasture or switched to forages may be affected; however, to a length of 3 inches or less. It is noninfected hays. Many animals most cases have been reported in best to sample several areas of the exhibiting poor performance will horses. Animals may become bale that do not appear to have gradually return to normal when an severely dehydrated and will visual defects, as well as those that alternative forage is supplied. usually die from kidney failure and have visual defects (i.e., mold). Providing other types of hay or shock. The intestines and urinary Consult with your county extension pasture and a grain supplement can tract are severely damaged. Animals agent about where to submit these reduce the effects of the toxins with blister beetle poisoning should samples and how to package them produced within endophyte-infected have the hay removed from the diet. for mailing to the laboratory. Make forages. Generally, diluting the The hay should be destroyed sure everything is labeled properly. infected fescue in the diet is an because the toxicity does not lessen The cost of the analysis may vary effective management technique. with time. If it is not too far depending on what tests are run on Brahman and Brahman-cross cattle advanced, animals can be treated the sample. normally exhibit better tolerance for kidney failure and shock. The

24 more than the maturity of the 7) The availability of forage Summary crop at harvest. proteins to livestock can be reduced by spontaneous heating 1) Whether purchased or home­ 5) Use appropriate haymaking during bale storage. grown, it is always best to test techniques. Hay should be baled hay for nutritive value and at 18 and 20 percent moisture 8) Use good management balance livestock rations on for large round and conventional techniques when storing this basis. rectangular bale packages, large round bales outside. respectively. Specifically, try to maximize 2) Color is not a good predictor drainage away from the storage of forage nutritive value. Place 6) Generally, the unrelated area, maintain air movement emphasis on maturity, condition processes of rain damage to around the bales and limit and purity when making wilting forages, spontaneous bale/soil contact. visual appraisals. heating and weathering will all reduce DM recovery, sugar 9) Do not be deceived by what 3) Visual appraisals should not be content, digestibility and the appears to be relatively shallow relied on for developing a live­ energy value (TDN) of the weathered layers in hays stored stock feeding program. Hay forage. Conversely, the con­ outside. Weathered layers of should be tested to determine centrations of the most stable 4 to 6 inches can account for actual forage nutritive value. components of the plant are 20 to 30 percent of the bale increased by these processes, volume and may cause pro­ 4) Harvest forage crops at the resulting in elevated con­ ducers to greatly underestimate correct maturity. No factor centrations of NDF, ADF their losses. affects forage nutritive value and lignin.

25 DR. DIRK PHILIPP is Associate Professor - Forages, University of Arkansas Division of Agriculture, Department of Animal Science, Fayetteville, and DR. JOHN A. JENNINGS is Professor - Forages, University of Arkansas Division of Agriculture, Department of Animal Science, Little Rock.

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