Applied Beef Cattle Breeding and Selection Composite Populations Larry V. Cundiff ARS-USDA-U.S. Meat Animal Research Center 2008 Beef Cattle Production Management Series-Module V Great Plains Veterinary Education Center University of Nebraska, Clay Center September 18, 2008

Sire breedDam breedCalf breedWeaning wt HAHA430 AHAH416 AAAA405 HHHH395 HA = 430 =.5g H +.5 g A + h I ha + m A AH = 416 =.5g H +.5 g A + h I ha + m H AA = 405 = g A + + m A HH = 395 = g H + + m H (.5)(HA + AH) -.5 (AA + HH) = 423 – 400 = 23 = h I ah Estimating Heterosis for a specific two breed cross

HA = 430 =.5g H +.5 g A + h I ha + m A AH = 416 =.5g H +.5 g A + h I ha + m H AA = 405 = g A + + m A HH = 395 = g H + + m H In the above equations, HA denotes a crossbred calf with a Hereford sire and an Angus dam. AH denotes a crossbred calf with an Angus sire and a Hereford dam. HH denotes a straightbred calf with a Hereford sire and Hereford dam. AA denotes a straightbred calf with an Angus sire and Angus dam. g H denotes the additive breed effect for Herefords and g A the additive breed effect for Angus. h I ha denotes effect of individual hetersosis expressed by Hereford X Angus or Angus X Hereford reciprocal crosses. Note that h I ha = h I ha. m A denotes the maternal (MILK) breed effect for Angus and m H the maternal breed effect for Hereford dams.

C X A =.5g C +.5 g A + h I ca + m A C X B =.5g C +.5 g B + h I CB + m B C X AB =.5g C +.25 g A +.25g B +.5h I AC +.5h I BC +.5m A +.5 m B + h M AB C X BA =.5g C +.25 g B +.25g A +.5h I AC +.5h I BC +.5m A +.5 m B + h M AB.5[( C X AB) + (C X BA)] –.5[(C X A) + (C X B)] = h M AB Estimating Maternal Heterosis

C X A =.5g C +.5 g A + h I ca + m A C X B =.5g C +.5 g B + h I CB + m B C X AB =.5g C +.25 g A +.25g B +.5h I AC +.5h I BC +.5m A +.5 m B + h M AB C X BA =.5g C +.25 g B +.25g A +.5h I AC +.5h I BC +.5m A +.5 m B + h M AB In the above equations, the g A, g B and g C denote additive breed effects for breeds A, B and C respectively. h I CA, h I CB and h I AC denote individual heterosis effects for C X A (or A X C), C X B (or B X C), and A X C (or C X A) breed crosses, respectively. m A and m B denote maternal (MILK) breed effects for breeds A and B, respectively. h M AB denotes maternal heterosis expressed by A X B (or B XA) crossbred dams.

Composite populations can be used to exploit: HETEROSIS HETEROSIS COMPLEMENTARITY among breeds optimize performance levels for important traits and to match genetic potential with: COMPLEMENTARITY among breeds optimize performance levels for important traits and to match genetic potential with: Market preferences Feed resources Climatic environment

MARC I ¼ Limousin, ¼ Charolais, ¼ Brown Swiss, c Angus and c Hereford Limousin Charolais AngusHereford Brown Swiss (Braunvieh) MARC II ¼ Simmental, ¼ Gelbvieh, ¼ Hereford and ¼ Angus Angus Simmental Gelbvieh Hereford MARC III ¼ Pinzgauer, ¼ Red Poll, ¼ Hereford and ¼ Angus Pinzgauer Red Poll Angus Hereford

HETEROSIS EFFECTS AND RETAINED HETEROSIS IN COMPOSITE POPULATIONS VERSUS CONTRIBUTING PUREBREDS (Gregory et al., 1992) Composites minus purebreds Composites minus purebreds Trait F 1 F 2 F 3&4 Birth wt., lb d wn. wt., lb d wt., females, lb d wt., males, lb Age at puberty, females, d Scrotal circumference, in d weaning wt., (mat.), lb3336 Calf crop born, (mat.), % Calf crop wnd., (mat.), % d wn. wt./cow exp. (mat.), lb5537

Composite populations maintain heterosis proportional to heterozygosity (n-1)/n or 1 –  P i 2

MODEL FOR HETEROZYGOSITY IN A TWO BREED COMPOSITE Breed Breed of sire Dam½ A½ B ½ A ¼ AA ¼ AB ½ B ¼ BA ¼ BB (n-1)/n or 1 –  P i 2 =.50

MODEL FOR HETEROZYGOSITY IN A THREE BREED COMPOSITE Breed Breed of sire Dam.50 A.25 B.25 C.50 A.25 AA.125 BA.125 CA.25 B.125 BA.0625 BB.0625 CB.25 C.125 AC.125 BC.0625 CC 1 –  P i 2 = ( ) =.625

Weaning Wt Marketed Per Cow Exposed for Alternative Crossbreeding Systems Relative to Straightbreeding (%) Straight breeding breed rotation (A,B) breed rotation (A,B,C) breed rotation (A,B,C,D) breed composite (5/8 A, 3/8 B) breed composite (.5 A,.5 B) breed composite (.5A,.25 B,.25C) breed composite (.25A,.25B,.25C,.25D) F1 bull rotation (3-breed: AB, AC) F1 bull rotation (4-breed: AB, CD) Wean. wt H i H m marketed System (+ 8.5%) (+14.8%) per cow exp

Composite populations provide for effective use of HeterosisHeterosis Breed differencesBreed differences Uniformity and end product consistencyUniformity and end product consistency

Genetic Variation in Alternative Mating Systems Optimum Assumes that the Two F 1 ’s Used are of Similar Genetic Merit

Genetic potential for USDA Quality Grade and USDA Yield Grade is more precisely optimized in cattle with 50:50 ratios of Continental to British breed inheritance.

CEFFICIENTS OF VARIATION IN PUREBRED AND COMPOSITE POPULATIONS (Gregory et al., 1992) Trait Purebreds Composites Gestation length, d Birth wt d wn. wt d wt., females d wt., males Age at puberty (females) Scrotal circumference yr cow wt, lb yr height, in Steer carcass wt, lb Rib-eye area Retail product, % Retail product, lb.19.20

COMPLEMENTARITY is maximized in terminal crossing systems Cow Herd Small to moderate size Adapted to climate Optimal milk production for feed resources Terminal Sire Breed Rapid and efficient growth Optimizes carcass composition and meat quality in slaughter progeny Progeny Maximize high quality lean beef produced per unit feed consumed by progeny and cow herd

Rotational and Terminal Sire Crossbreeding Programs Cow AgeNo Breed Rotation A B   T x (A-B) Lbs. Calf/Cow 21% 18% 45% 55% 1/2A - 1/2B Two Breed Composite

Weaning Wt Marketed Per Cow Exposed for Alternative Crossbreeding Systems Relative to Straightbreeding (%) Straight breeding breed rotation (A,B) breed rotation (A,B,C) breed rotation (A,B,C,D) breed composite (5/8 A, 3/8 B) breed composite or F1 bulls (.5 A,.5 B) breed composite (.5A,.25 B,.25C) breed composite (.25A,.25B,.25C,.25D) F1 bull rotation (3-breed: AB, AC) F1 bull rotation (4-breed: AB, CD) Wean. wt Terminal H i H m marketed cross a System + 8.5% +14.8% per cow exp (+5% wt/calf) a Assumes 66 % of calves marketed (steers and heifers) are by terminal sire breed out of more mature age dams and 33% are by maternal breeds (steers only).

SUMMARY

General Considerations Rotational SystemsRotational Systems Provide for more effective use of HeterosisHeterosis Composite populationsComposite populations Provide for more effective use of Breed differencesBreed differences Uniformity and end product consistencyUniformity and end product consistency

Figure 6. Use of heterosis, additive breed effects and Complementarity with alternative crossbreeding systems.

Advantages of terminal sire crossing systems are not as great today as 30 years ago due to similarity of breeds for rate and efficiency of growth. Advantages of terminal sire crossing systems are not as great today as 30 years ago due to similarity of breeds for rate and efficiency of growth. However, differences between British and Continental breeds in carcass traits are still significant and relatively large. However, differences between British and Continental breeds in carcass traits are still significant and relatively large. Inter generation fluctuations in mean performance for carcass traits are still large and significant. Inter generation fluctuations in mean performance for carcass traits are still large and significant. For carcass traits, uniformity and end-product consistency can still be enhanced by use of composite populations or hybrid bulls. For carcass traits, uniformity and end-product consistency can still be enhanced by use of composite populations or hybrid bulls. Adaptation to intermediate subtropical/temperate environments can be optimized with greater precision by use of composite populations or hybrid bulls. Adaptation to intermediate subtropical/temperate environments can be optimized with greater precision by use of composite populations or hybrid bulls. Implications for Crossbreeding

Module IV Applied Animal Breeding and Selection Homework questions assigned September 18 To be returned by October 23, 2008 ( to: The Brangus breed has a genetic composition of 5/8 Angus and 3/8 Brahman breeding. 1) What is the expected heterozygosity or level of Brahman X Angus heterosis expected in the Brangus breed (show work)? 2) How would you expect the effect of heterosis for Brangus to compare to that in a breed with a composition of 5/8 Angus and 3/8 Shorthorn, why or why not? (In other words, would effects of heterosis be the same, or more, or less for Brahman X Angus crosses than for Angus X Shorthorn crosses, why or why not?) 3) What is the expected level of heterosis in a four breed composite founded with ¼ breed A, ¼ breed B, ¼ breed C, and ¼ breed D inheritance (show work)? 4) State the location and describe a typical production environment for cow herds where you reside or provide service. 5) If you were to develop a composite population adapted to this production environment, what foundation breeds would you select? 6) What proportions of each breed would you use in the composite population? 7) What would the expected level of heterosis be in your composite population (show work)? 8) Why would you select these breeds (Discuss the merits of each breed selected for additive direct and maternal breed effects).