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Lecture 3-22 Exam 3 Breeds

Fine Medium Coarse Most important breeds? Why so many in US?. Lecture 3-22 Exam 3 Breeds. Purebred Operations: More records required Registration work Traits important to breed. Performance Records. 1. Selection differential 2. Heritability 3. Generation interval.

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Lecture 3-22 Exam 3 Breeds

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  1. Fine Medium Coarse Most important breeds? Why so many in US? Lecture 3-22 Exam 3Breeds

  2. Purebred Operations: More records required Registration work Traits important to breed Performance Records

  3. 1. Selection differential 2. Heritability 3. Generation interval Genetic Improvement: 3 factors

  4. SD is the superiority of replacements compared to flock average. Example: Average adjusted WW 60 Replacement Ewes - 70 70 - 60 = 10 x .5 x .2 SD = 1.0 Selection Differential

  5. Replacement Ram = 85 pound adj. ww 85 - 60 = 25 x .5 x .2 SD = 2.5 Total SD = 2.5 + 1.0 = 3.5

  6. Sires provide more improvement SD with only one trait More traits - SD per trait decreases Limits to Selection Differential

  7. % of what you see which is due to genetics. Traitsh2 Reproduction .1 - .2 Growth .25 - .40 Carcass .3 - .5 Wool .4 - .6 Heritability

  8. Low h2 traits require multiple records Example: Lambs born h2 - .10 with r < .20 Repeatability - likelihood that a ewe twinning in 2011 will twin in 2012. Lamb crop in U.S. has not increased. Number born increases with ewe age

  9. Selection based on one record must account for fixed effects. Ex: 5 year old ewe with twins in 2011 Individual record not important. Perspective buyers What has she done relative to flock average each of past five years

  10. Wool traits highly heritable highly repeatable one record of performance

  11. Generation Interval How fast the flock turns over. GI = Average Ewe + Average Ram Age 2 4 + 2 = 3.0 2

  12. GI - Smallest possible = 1 Economic suicide Why ?? Best Solution = let ewe age float Rams use only one year Use older rams from other flocks

  13. Economic Traits Ewes: Pounds Weaned Mothering ability Milking ability Prolificacy Growth Hardiness and Longevity Extended Breeding Season Clean Wool

  14. Economic Traits Rams: Offspring Vigor and Livability Rate of Gain Feed Efficiency Breeding Capacity Carcass Cutability Lambing Ease

  15. Genetic Improvement Set Selection Goals Identify Superior Individuals NSIP - uses all performance records - fair comparisons via contemporary groups - provides genetic estimates on animals without records ex. rams and young lambs

  16. NSIP Traits Maternal Lambs born Pounds Weaned Maternal Milk Growth 60, 120, 365 Wool Grease Fleece Weight (GFW) Fleece Length Fleece Grade

  17. Adjust for: Dam Age Type of Birth and Rearing Age Adjustment Sex Fixed Effects

  18. Contemporary groups What is it? When are they needed?

  19. Lamb Plan Wool Plan Ewe Byte Group Breeding Schemes Great Britain SUFFOLK SIRE REFERENCE SCHEME Canada Western Suffolk Sire Reference program Ontario Suffolk Sire Refernece program Why is group breeding successful. Other Sheep Improvement Plans

  20. Why does sheep industry not embrace genetic improvement? Purebred breeders Commercial producers

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