Extension Bulletin E-270 New June 1999 Crossbreeding Systems for Beef Cattle

Harlan Ritchie, B. Dennis Banks, Daniel Buskirk, Joel Cowley and David Hawkins Department of Animal Science

sis is that expressed by the crossbred Reasons for Crossbreeding Heterosis and Its Effects calf; maternal heterosis is that Crossbreeding can increase levels of The level of heterosis tends to be expressed by the crossbred dam. production in livestock in two ways: inversely proportional to heritability. Table 1 illustrates the relationship 1. Complementarity utilizes the In moderately to highly heritable between heritability and heterosis in desirable characteristics of two or traits, such as carcass characteristics, various traits. It is important to note more breeds to achieve a higher fre­ the level of heterosis is low. On the that reproduction traits, which are low quency of desired genes among the other hand, in traits having low heri­ in heritability and for that reason can­ crossbreds than could be found within tability, such as fertility and Hvability, not be changed readily through selec­ a single breed. In other words, the heterosis is high. In general, heterosis tion within a pure breed, can be strong points of one or more breeds is expressed to a greater degree in markedly improved through the can be used to compensate for the reproduction and in traits expressed effects of heterosis. Conversely, car­ weak points of another breed. up to weaning time. cass traits exhibit little or no heterosis Geneticists refer to this as additive Heterosis is classified as either indi­ but respond well to selection within a gene effects. vidual or maternal. Individual hetero­ breed. As animals in a cross become geneticallv more divergent or unlike, 2. Heterosis (hybrid vigor) results from non-additive gene effects. It is Table 1. Heritability and heterosis estimates for defined as the percent of superiority some economically important traits. expressed in a trait by crossbred prog­ eny over the average of the parent Totol breeds in the cross. Heterosis is calcu­ Troit Heritability0 heterosis0 (%) lated by the following formula:

% heterosis = Calving rate .02-.17 6 crossbred avg. - straightbred avg. ,QQ Calf survival to weaning .10 — .15 4 straightbred avg. Weaning rate .17 8 As an example, assume that the two Birth weight direct .31 6 parent breeds in a cross had weaning Weaning weight direct .24 11 weight averages of 575 and 475 Milk production .20 9 pounds and their crossbred progeny Postweaning gain .31 3 averaged 550 lb. The percent of het­ Yearling weight .33 4 erosis would be: Mature cow weight .50 1 Feed conversion (TDN/gain) .32 -2 550-525 x 100 = 4.8% Dressing % .39 0 525 Rib eye area .42 2 The basic objective of crossbreeding % cutcbility/retail product .47 0 systems is to optimize simultaneously Marbling/quality grade .38 2 the use of heterosis and breed differ­ Tenderness .29 0 ences within a given production and marketing environment. The produc­ 0 Koots efo/. (1994). tion environment includes feed b Kress and Nelsen (1998). resources as well as climatic condi­ tions. MICHICAN STATE EXTENSION heterosis is usually higher. As an example, when Bos taurus (European) Table 2. Effects of individual and maternal heterosis in crossing Herefords, Angus breeds are crossed with Bos indicus and Shorthorns in Fort Robinson Research Station study.0 (Brahman) breeds, the effects of het­ erosis are greater than those shown in Phase 1, Phase II, Total Table 1. On the other hand, when individual heterosis, maternal heterosis, heterosis, bloodlines within a breed of cattle are % % % crossed, little, if any, heterosis is Weaning % +3.0 +6.4 +9.4 expressed. Weaning wt. +4.6 +4.3 +8.9 The cumulative effects of individual Weaning wt./cow exposed +8.5 +14.8 +23.3 and maternal heterosis on calf weight weaned per cow exposed can be very ° Cundiff and Gregory (1977); Gregory and Cundiff (1980). dramatic. This is shown in Table 2, which summarizes a long-term cross­ breeding study conducted in two maternal heterosis and one-third (8.5 3. A.I. or natural service? More phases at the Fort Robinson Research percent) to individual heterosis. complex systems can be used if Station in Nebraska. Phase I mea­ Experiments involving Brahman x you are set up for A.I. sured individual heterosis by compar­ European crosses have shown even ing crossbred calves against straight- 4. Can high-quality replacements greater cumulative increases over the bred calves, both of which were be purchased at a competitive average of the straightbred parents. raised by straightbred dams. Weaning price? If so, crossbreeding is made percentage was 3 percent higher for If your goal is to maximize heterosis, easier. the following requirements should be crossbred calves because of 3 percent 5. Quantity and quality of labor: met (assuming natural service and higher livability. This, coupled with a More elaborate systems can be raising your own replacements): 4.6 percent heavier weaning weight, utilized as family or hired labor resulted in 8.5 percent more calf 1) Avoid backcrossing and subsequent becomes more plentiful and weight weaned per cow exposed in loss of heterosis by making the most skilled. favor of the crossbred calves. divergent matings possible. 6. Facilities: With better facilities, The effects of maternal heterosis were 2) Two or more breeding pastures are more complex systems are consid­ measured in Phase II by comparing needed. ered feasible. crossbred against straightbred cows, both of which were raising crossbred 3) Two or more breeds of bulls are 7. Available capital: Developing a calves. Weaning percentage was 6.4 needed. well organized crossbreeding sys­ tem generally requires more capital percent greater for the crossbred cows 4) All females must be identified by outlay than a straightbreeding pro­ because of a higher conception rate; breed of sire and year of birth. there was no difference in calf livabil­ gram. Certain crossbreeding systems can ity. Because the crossbred cows 8. Region of the country: In some milked heavier, their calves weighed help mitigate some or all of the above requirements. regions of the United States, com­ 4.3 percent more at weaning time. plex systems may not be feasible. These two factors together resulted in Crossbreeding Systems For example, in the extensive 14.8 percent more calf weight weaned intermountain areas of the West, per cow exposed for the crossbred Factors to be considered when the more elaborate systems may dams. In the third column of Table 2, choosing a system: not be workable. the combined effects of individual 1. Size of herd: The smaller the herd, and maternal heterosis are summa­ 9. Willingness to maintain records: the less complex the system should Complex systems should be avoid­ rized. Crossbred cows raising cross­ be. bred calves weaned 23.3 percent more ed if the producer has a problem calf weight per cow exposed than 2. Number of breeding pastures: If with identification and records. straightbred cows raising straightbred you use natural service, the number 10. Factors associated with choice calves. About two-thirds (14.8 per­ of available breeding pastures will of breeds in the system: cent) of this advantage was due to be a factor in how elaborate the system can be. a. Feed resources - abundant, average or sparse? Table 3. Comporison of crossbreeding systems. % of % of the marketed colves % of maximum Est. % inc. in lb. Minimum no. Mating cow generated by possible caff weaned per of breeding Minimum type herd this mating heterosis0 cow exposed postures herd size

Two-breed rotation at equilibrium A-B rotation 100 100 67 16 2 50

Three-breed rotation ot equilibrium A-B-C rotation 100 100 86 20 3 75

Static terminal sire system A-A 25 17 B-A 25 17 C x (B-A) 10 13 T x (B-A) 40 53 Overall 100 100 86b 20 100

Two-breed rotation and terminal sire system (rota-terminal) A-B rotation 50 33 T x (A-B) 50 67 Overall 100 100 90° 21

Terminal sire x purchased F| females T x (A-B) 100 100+ b 28 Any size

Rotate sire breed every 4 years A-B rotation 100 50 12 Any size A-B-C rotation 100 67 16 Any size

Composite breeds 2-breed composite d4 A, KB) 1 50 12 Any size 3-breed composite (^ A, %i,%0 1 100 63 15 Any size 4-breed composite (X A, x B, % C, K D) 1 100 75 17 Any size

Rotating unrelated F| bulls A-B ^ A-B 100 100 50 12 1 Any size A-B <-* A-C 100 100 67 16 1 Any size A-B ++ C-D 100 100 83 19 1 Any size

Based on heterosis effects of 8.5% for individual traits and 14.8% for maternal traits.

Assumes a 10% increase in breeding value for caff weight produced per cow exposed to terminal sires.

b. Climate - severe, average or d. Breed availability in your In the following sections, systems stress-free? region. that are in general use across the country will be discussed. A summa­ c. Frame size required by the e. Breed preferences in the ry of these systems is presented in market - in other words, how marketplace. Table 3. This publication does not much should the carcasses necessarily include all systems that from the progeny weigh when have been used or recommended. they reach Choice grade?

3 Two-breed Rotation (Fig. 1) The two-breed rotation is initiated by mating females of breed A to bulls of breed B, with the resulting BA replacement heifers mated to bulls of breed A for their entire lifetime. In each succeeding generation, replace­ ment heifers are bred to bulls of the opposite breed from their sire. Following are other features of this system: 1. A minimum of two breeding pas­ tures are required if natural ser­ vice is used. 2. To make the system most practi­ cal, minimum herd size is about 50 cows. 3. Replacement heifers must be identified by breed of their sire. 4. After a few generations, level of heterosis stabilizes at about 67 percent of maximum possible (23.3%), resulting in an expected 16 percent increase in pounds of calf weaned per cow exposed over the average of the parent breeds. 5. Rotational systems should involve breeds that are reason­ ably comparable in certain bio­ logical characteristics such as birth weight, mature size, frame 3. Replacement heifers must be more than three breeds. With more size and milk production to mini­ identified by breed of sire. They breeds, a slight increase in heterosis mize calving difficulty in first- are to be mated to the breed of is achieved, but management calf heifers, stabilize nutrition sire to which they are most dis­ becomes more difficult and herd size and management requirements in tantly related. the cow herd, and avoid large should be proportionately larger. swings in biological type from 4. Level of heterosis stabilizes at Static Terminal Sire System (Fig. 3) one generation to another. about 86 percent of maximum As shown in Table 3, the static termi­ possible, resulting in an expected Three-breed Rotation (Fig. 2) nal sire system involves the produc­ 20 percent increase in pounds of The three-breed rotation follows the tion of a straightbred unit (A-A) (25 calf weaned per cow exposed. same pattern as the two-breed rota­ percent of cow herd) that generates tion, but a third breed is added to the 5. As with the two-breed rotation, female replacements for this unit as system. the breeds chosen should be rea­ well as replacements for a second sonably comparable in birth unit. Females in the second unit are 1. A minimum of three breeding weight, mature size, frame size mated to bulls of a second breed (B) pastures is needed. and milk level. (25 percent of cow herd) to produce 2. Minimum herd size should be crossbred females (B-A) (50 percent Four- or Five-breed Rotations of cow herd), which after production somewhere around 75 cows. Rotational crossbreeding may involve

4 of the first calf are mated to terminal bulls of a smaller breed (C) to pro­ herds of more than 100 cows. The sires (T) with high breeding value for duce their first calves to minimize disadvantages of this system are its growth rate. All progeny of both calving difficulty. All of the C-B-A complexity from a management sexes are marketed. Other calves calves also go to market. standpoint and the inherent limitation marketed are the male calves pro­ on the percentage of the herd using This system requires four breeds of duced from A x A and B x A matings. heterosis. Maternal heterosis can be bulls and a minimum of four breed­ Females placed in the terminal sire used in only 50 percent of the herd ing pastures. It should be used only in component of the herd are mated to and individual heterosis in 75 percent of the herd. Another disadvantage is Figure 3 that little selection pressure can be applied among females entering the cow herd. Nearly all females (about 90 percent) produced by the straight- bred (A) cows are required as replacements. Additionally, only about 53 percent of the marketed calves are sired by the terminal breed. Assuming the levels of heterosis shown in Table 3 and that the termi­ nal sire breed (T) increases calf weaning weight by 5 percent, the pounds of calf weaned per cow exposed will be increased by about 20 percent. In the final analysis, this system has no more to offer than the three-breed rotation. For that reason, it has little to recommend it. Rotational-terminal Sire (Rota-terminal) System (Fig. 4) As shown in Table 3, this system entails the use of rotational matings of maternal or multipurpose breeds Figure 4 (A and B) in 50 percent of the herd to provide crossbred replacement females for the entire herd. The objective is to provide the A-B replacements by mating the younger cows (1-, 2- and 3-year-olds), when calving difficulty is expected to be greatest, in the rotational system and to mate only mature cows to terminal sires (T) after replacement require­ ments have been met. The rotational portion of the herd will require about half of the cows, leaving the other half to be mated to the terminal sire breed. Other features of the system are: 1. At least three breeding pastures are required. 2. Minimum herd size is about 100 tem because it allows a producer to 4. If virgin heifers are purchased, cows. use highly specialized maternal they should be mated to an easy- females that are fertile and easy- 3. Cows must be identified by year calving sire for their first calf. keeping and mate them to highly spe­ of birth as well as breed of sire. 5. It maximizes use of individual cialized terminal sires that excel in and maternal heterosis as well as 4. Approximately two-thirds of the growth rate and carcass traits. Other breed complementarity. The marketed calves are sired by the characteristics of the system are: expected increase in pounds of terminal breed. 1. It requires only one breeding calf weaned per cow exposed is 5. The expected increase in pounds pasture and one breed of sire. 28 percent. of calf weaned per cow exposed 2. It's adaptable to any herd size. 6. There is some risk of introducing is about 21 percent. 3. No identification by breed of sire disease when replacements are 6. This system requires a relatively or by year of birth is needed. purchased. high degree of management to make it run smoothly. If a 3-breed rotation is used to pro­ Figure 5 vide replacements, the expected increase in pounds of calf weaned would be about 24 percent. However, the number of breeds of bulls and number of breeding pas­ tures required increases to four. Less Complex Crossbreeding Systems Many cow herds are too small or lack the resources needed to successfully run the more complex systems described above. Nevertheless, it is still possible to harvest a significant percentage of the benefits of cross­ breeding through some relatively sim­ plified systems.

Terminal Sire x Purchased F, Females (Fig. 5) This system is more of a management and economic decision than it is a crossbreeding system. Nonetheless, it is the simplest, fastest and most effec­ tive means of utilizing the advantages of crossbreeding - heterosis and breed complementarity. As indicated in Table 3, both individual and mater­ nal heterosis are maximized. The sys­ tem involves the purchase of F, (two- breed cross) replacement females, mating them to a terminal breed of bull and marketing all of the progeny. No heifer calves are retained as replacements. It is an attractive sys­

6 Replacements need not be purchased then, about 80 percent of the founda­ mum possible heterosis (=J-=J = 75%). every year. Depending on the age tion cows will have been culled from For more detailed information on breakdown of the original cows, the herd. From that point on, each composites, refer to Extension bul­ replacements may be needed only succeeding breed of bull should be letin E-2702, "Development and Use every 2 to 5 years. This gives the herd used for about 4 years to harvest the of Composite Breeds: A Summary." owner the flexibility of deferring most heterosis from the system. On Rotating Crossbred (Hybrid) Bulls female purchases until prices are an average, heterosis will be 50 per­ Hybrid bulls offer an alternative lower and/or supplies are more plenti­ cent of maximum in a two-breed method of utilizing the composite ful. This system is particularly well rotation, resulting in a 12 percent concept. As shown in Table 3, using adapted for producers who have feed increase in pounds of calf weaned per unrelated Fj bulls composed of the and facilities for growing and finish­ cow exposed. In a three-breed rota­ same two breeds (A-BHA-B) can ing cattle. Weaned crossbred heifers tion, heterosis will be 67 percent of result in retention of 50 percent of could be purchased in the fall and maximum, resulting in a 16 percent maximum possible heterosis. Rotating grown out over the winter. In the boost in productivity. Although this Fi bulls that have one breed in com­ spring, the better heifers could be system sacrifices some heterosis and mon (A-BHA-C) can result in 67 per­ sorted off for breeding and the complementarity, its simplicity makes cent heterosis. Rotation of Fj bulls remainder finished out for slaughter. it a useful one for small herds. having no breeds in common For those who do not have such feed Composites (A'BHC-D) can offer 83 percent of and facilities, the heifers could be maximum heterosis, nearly equal to grown out and bred A.I. in a profes­ In recent years, there has been increased interest in the formation of that achieved with a three-breed rota­ sional heifer development center. composite populations, based on a tional system. The first system The terminal sire x F, female system multibreed foundation. Once a com­ (A-B<->A-B) would be especially use­ should be given serious consideration posite population is formed by its ful in small herds because it requires by smaller herd owners if a depend­ developer(s), commercial customers only one breeding pasture. Another able supply of replacement females is can purchase the bulls and manage variation of this system would be to available. It is entirely possible that their herds as straightbreds. Con­ rotate different breeds of F, bulls quality crossbred heifers can be pur­ sequently, the problems that small (AB, CD, E-F, etc.) every 4 years. chased and raised as economically as herds encounter when they try to use But to avoid wide generational you can develop your own replace­ complex systems can be averted. swings in biological type, breeds A, C ments. Not including interest, it takes and E should be similar in type, as To retain heterosis in a composite $400 to $500 to rear a replacement should breeds B, D and F. population that is closed to outside heifer from weaning time at 7 months genetics, inbreeding must be avoided. to first calving at 24 months of age. Add to this the weaned heifer calf's To do so, each foundation breed Matching Systems initial value of $350 to $500, and the should be widely sampled (15 to 20 total cost at 24 months may range sires per breed) and involve 25 or With Situations from $750 to $1,000. more sires per generation. This trans­ Some typical situations are listed in lates to a population of at least 500 to the following paragraphs. Matched up Rotate Sire Breed Every Four Years 1,000 cows. In small, more tightly with them are the systems that would (Fig. 6) bred populations, inbreeding depres­ appear to be applicable. This is by no This system entails the use of only sion can be mitigated by introducing means meant to be a complete list of one sire breed for several years, then unrelated genetics from time to time. all possible situations. As herd size rotating to a second breed, a third, Assuming that inbreeding is avoided, increases and more breeding pastures etc. Replacement heifers are produced the percent of maximum possible het­ are available, the number of options within the herd. As shown in Table 3, erosis that can be retained ranges increases. only one breeding pasture is needed from 50 percent for a two-breed com­ 1. Small herd size (under 50 cows); and it is an appropriate system for posite to 87 percent for an eight- natural service; one breeding pas­ any size of herd. No identification by breed composite. Retained heterosis ture; limited labor; limited capi­ sire breed or year of birth is neces­ can be estimated from the formula tal; females cannot be purchased. sary. itjl, in which n is the number of a. Rotate sire breed every 4 years. If you start with a herd of straightbred breeds in the composite. For exam­ cows, the first breed of bull should be ple, a four-breed composite would be b. Composite breed. expected to retain 75 percent of maxi­ used for about five calf crops. By c. Rotate Fj bulls.

7 2. Same situation as above, except 4. Herd of 50 cows; one breeding 6. From 75 to 100 cows; natural good crossbred females can be pasture; A.I. service; adequate service; at least three breeding purchased economically in the facilities, labor arid capital; pastures; adequate labor and area. females cannot be purchased. capital. a. Terminal sire x purchased Fj a. Two-breed rotation. a. Three-breed rotation. females. b. Three-breed rotation is feasible b. Terminal sire x Fj females (if 3. Herd of 50 cows; natural service; at from a management standpoint available). least two breeding pastures; limited but involves a lot of breeds for c. Composite breed. labor and capital. the number of calves that d. Rotate F, bulls. a. Two-breed rotation. result. 7. More than 100 cows; natural ser­ b. If Fj females are available eco­ 5. From 50 to 100 cows; one breed­ ing pasture; A.I. service; ade­ vice; at least three breeding pas­ nomically, purchase them and tures; adequate labor and capital. mate to terminal sire. quate facilities, labor and capital; females cannot be purchased. a. Rota-terminal system. c. Rotate sire breed every 4 years. a. Two-breed rotation. b. Three-breed rotation. d. Composite breed. b. Three-breed rotation. c. Terminal sire x F, females (if e. Rotate F] bulls. available). d. Composite breed. e. Rotate F, bulls.

Selected References Gregory, K.E., and L.V. Cundiff. 1980. Kress, D.D., and T.C. Nelsen. 1988. Crossbreeding in beef cattle: evaluation of Crossbreeding beef cattle for Western Cundiff, L.V., and K.E. Gregory. 1977. Beef systems. J. Anim. Sci., 51:1224. range environments. Tech. Bull. No. cattle breeding.Agriculture Information 88-1. Nevada Agr. Exp. Sta., Reno, Bull. No. 286. ARS, USDA. Gregory, K.E., L.V. Cundiff and R.M. Koch. 1997. Composite breeds to use heterosis Kress, D.D. 1994.Crossbreeding with a Gosey, J.A. 1979. Crossing the breeds. Proc, and breed differences to improve efficien­ The Range Beef Cow Symposium VI, Dec. new target Proc. Beef Improvement cy of beef production. Tech. Bull. ARS, 3-5, Cheyenne, Wyo. Federation 26th Annual Conf., June 1- USDA, and Univ. of Nebraska. 4, Des Moines, Iowa. Gosey, J.A. 1994. The role of hybrid bulls in Koots, K.R., J.P. Gibson, C. Smith and J.W. defying genetic antagonisms. Wilton. 1994. Analysis of published genet­ Proc,Northwest Kansas Cow-Calf ic parameter estimates for beef production Seminars, Feb. 3-4, Colby, Kansas. traits. 1. Heritability. Animal Breeding Abstracts., 62 (5): 309.

MSU is an affirmative-action, equal opportunity institution. Michigan State University extension programs and materials are open to all without regard to race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, marital status, or family status. • Issued in furtherance of Extension work in agriculture and home economics, acts of May 8 and June 20, 1914, in cooperation with the U.S. Department of Agriculture. Arlen Leholm, Extension Director, Michigan State University, E. Lansing, Ml 48824. • This information is for educational purposes only. Reference to commercial products or trade names does not imply endorsement by MSU Extension or bias against those not mentioned. This bulletin becomes public property upon publication and may be printed verbatim with credit to MSU. Reprinting cannot be used to endorse or advertise a commercial product or compa­ ny. Produced by Outreach Communications and printed on recycled paper. New 7:99-500-KMF/CW, Price $2.00, for sale only