David L. Thomas Department of Animal Sciences University of Wisconsin-Madison

1. Basics of Sheep Breeding for Commercial Flocks David L. Thomas Department of Animal Sciences University of Wisconsin-Madison

2. Production (P) of a sheep is dependent upon: - The genes of the sheep (genotype, G) - The environment in which the sheep is raised (E), i.e. nutrition, health program, housing, temperature, humidity, parasite challenge, etc. Production = Genotype + Environment P = G + E = +

3. Production (P) of a sheep is dependent upon: Production = Genotype + Environment P = G + E Genotype = Breeding Value (BV) + Gene Combination Value (GCV) Therefore: Production = Breeding Value + Gene Combination Value + Environment P = BV + GCV + E

4. BV = breeding value = sum of the independent effects of each allele affecting the trait (+ or – deviation) Individual alleles, and therefore independent allele effects, are passed from parent to offspring, so a sheep’s BV is used to predict the performance of its progeny (i.e. EPD). The proportion of differences between sheep in performance that is due to the differences in their breeding values is heritability (h2) of that trait. h2 = BV variation / Performance variation

6. Visual Traits Characteristics that you can see, such as: Conformation Height Length Wool quality are highly heritable. If such traits are of great economic importance in your flock, select sheep that have the appearance you desire.

7. – In Changing Conformation U.S. Southdowns – Then and Now Selection for Conformation is Effective However, conformation is not highly correlated with performance for many production traits.

8. 1st Place Fall Ram Lamb, 2005 IL State Fair Brockmann Family, IL U.S. Shropshires: 1946 – 1961 - 2005

9. Production Traits Traits that result in improved lamb, wool, and/or milk production Litter size, lamb survival, milk production, weaning weight, postweaning gain, loin eye area, fat thickness, fleece weight, disease resistance, etc.

10. Production Traits Steps in the selection of replacement ewes for production traits • Initial selection on performance records – without looking at the animals. Select 10 – 15% more animals than needed. • 2. Visual appraisal of only the animals selected on the basis of records. Cull the poorest 10 – 15% on visual appraisal.

11. 1. Individual identification of ewes and lambs 4. Weigh lambs at weaning and record date of weaning Selection of Replacement Ewe Lambs Minimum record-keeping requirements: • Record birth date ID, dam, and sex of each lamb 3. Record number of lambs born and raised by each ewe and birth-rearing type of each lamb UW

12. Adjust Litter Size for Age of Ewe Adjust litter size for age of the ewe. Select replacement ewe lambs from dams with high average adjusted litter size.

13. Example of Adjusted Litter Size Even though both ewes produced 3 lambs in two years, Ewe 722 is expected to be genetically superior, and her ewe lambs should be considered as replacements.

14. Estimated Breeding Value (EBV) Difference in EBV between 722 and 205 based on their first record: EBV = h2 (1.48 – 1.00) = .10 (.48) = .048 lambs 722 is estimated to have a genetic superiority of .05 more lambs per litter than 205. Difference in EBV between 722 and 205 based on the average of their two records: EBV = h2average of 2 records (1.91 – 1.52) = .17 (.61) = .104 lambs 722 is estimated to have a genetic superiority of .10 more lambs per litter than 205 based on two records.

15. EPDs are calculated by the National Sheep Improvement Program (NSIP) Selection of Replacement Rams Most commercial flocks purchase their rams Since fewer rams are selected than ewes, rams should have higher genetic values than ewes Most of the genetic improvement in flocks is the result of ram selection rather than ewe selection Select rams from flocks that are serious about genetic improvement for production traits The most accurate estimate of genetic merit is the Expected Progeny Difference (EPD)

16. Suffolk Genetic Trend and Performance

17. Almost all commercial flocks should be utilizing crossbreeding

18. Crossbreeding – Why? • 1. Breed complementarity – Utilize the strong points of two or more breeds in a crossbreeding system to maximize performance. • Good example: • Suffolk ram x Polypay ewe • Poor example: • Polypay ram x Hampshire ewe Paternal male x Maternal female Maternal male x Paternal female 2. Hybrid vigor or heterosis – increased performance of crossbreds compared to the purebreds that make up the cross.

19. Hybrid Vigor Example – 60-day Weaning Weight Suffolk x Suffolk lambs = 60 lb. Polypay x Suffolk and Suffolk x Polypay lambs = 58 lb. Hybrid vigor = 58 – 55 = 3 lb. Average of purebred Suffolk and Polypay lambs = (60 + 50) / 2 = 55 lb. % HV = ((crossbred – purebred) / purebred) x 100 = ((58 – 55) / 55) x 100 = (3 / 55) x 100 = .05 x 100 = 5 % Polypay x Polypay lambs = 50 lb.

21. Maternal and Paternal Hybrid Vigor Maternal HV - increased performance of an individual due to its dam being crossbred (or from a mating utilizing a crossbred dam) Paternal HV - increased performance of an individual due to its sire being crossbred (or from a mating utilizing a crossbred sire)

24. + 43 % Cross rams x Cross ewes = 4-breed cross lambs Paternal HV = 3% Pure rams x Cross ewes = 3-breed cross lambs + 39 % Maternal HV = 18% + 18 % Pure rams x Pure ewes = 2-breed cross lambs Individual HV = 18% 0 Pure rams x Pure ewes = Pure lambs

25. Crossbreeding Systems

26. Crossbreeding Systems 100 ewe flock All ewe replacements are produced within the flock All rams are purebred and purchased. No pure Finnsheep ewes are used.

27. 87 lb. lamb weaned per ewe exposed 3-Breed Terminal Crossbreeding System Market Lambs Dorset rams x 20 Dorset ewes Finnsheep rams x 25 Dorset ewes Male lambs and a few cull ewe lambs Hampshire rams x 55 FinnxDorset ewes All Hampshire-sired lambs Advantages: Good breed complementarity Disadvantage: Too many purebred ewes – reduced maternal hybrid vigor

28. Male lambs and cull ewe lambs 85 lb. lamb weaned per ewe exposed 3-Breed Rotational Crossbreeding System Finnsheep rams x Dorset ewes Market Lambs Hampshire rams x FxD ewes Dorset rams x H(FD) ewes Finnsheep rams x D(HFD) ewes Hampshire rams x F(DHF) ewes (system continues to rotate sire breed) Advantages: All ewes (after start) and all lambs are crossbred – good use of individual and maternal hybrid vigor (86% of maximum) Disadvantage: Poor breed complementarity

29. 95 lb. lamb weaned per ewe exposed 3-Breed Roto-Terminal Crossbreeding System Terminal (65-75 ewes) Market Lambs Rotation (25-35 ewes) F rams x D ewes Hamp-sired lambs, F- and D-sired male lambs, some F- and D-sired ewe lambs FD ewes x Hamp rams D rams x FD ewes F rams x DF ewes DF ewes x Hamp rams D rams x FD ewes FD ewes x Hamp rams (system continues) Advantages: 1) All ewes (after start) and all lambs are crossbred – good use of individual and maternal hybrid vigor (67% of Mat HV, 67% & 100% Ind HV) 2) Good breed complementarity Disadvantage: ?

30. Final Comments on Crossbreeding 1. Good crossbreds result from good purebreds. 2. Don’t expect hybrid vigor to compensate for poor or inappropriate genetics. 3. Limit the number of breeds to those that have high levels of performance. 4. Hybrid vigor is maximized when no breeds are in common in the sire and dam. 5. More hybrid vigor is obtained when less related breeds are crossed. 6. An organized crossbreeding system is needed to take best advantage of hybrid vigor and breed complementarity.

31. Effective Utilization of Genetics in the U.S. Sheep Industry breed selection + selection in the purebreds + crossbreeding Where the commercial sheep industry should be!! breed selection + selection in the purebreds Where the purebred sheep industry should be!! Performance breed selection – without genetic improvement over time in the purebreds Years

33. Adjustment of Lamb Weaning Weight for Age at Weighing 60-d WW = (((actual WW – actual BW) / actual wean age, days) x 60) + actual BW

34. Adjustment of Lamb Weaning Weight for Age of Dam, Sex of Lamb, and Type of Birth-Rearing of Lamb

35. Final Adjustment of Lamb Weaning Weight for Age at Weighing, Age of Dam, Sex of Lamb, and Type of Birth-Rearing of Lamb Adj. 60-d WW = 60-d WW x Age of Dam Adj. x Sex of Lamb Adj. x Type of Birth-Rearing of Lamb Adj. Lamb 9038 is estimated to be genetically superior over lamb 9005 for weaning weight and should be selected.

36. Maximize HV HV is maximized when there are no breeds in common between the sire and dam. Hampshire ram x Polypay ewe = Hamp x Polypay cross lambs = ½ H, ½ P lambs (100% maximum HVI) (Polypay x Hampshire) ram x (Polypay x Suffolk) ewe = (P x H) x (P x S) lambs = ½ P, ¼ H, ¼ S lambs (75% maximum HVI) Hampshire ram x (Hampshire x Polypay) ewe = H x (H x P) lambs = ¾ H, ¼ P lambs (50% maximum HVI) Hampshire ram x Hampshire ewe = Hampshire lambs (no HVI)