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Considering Inbreeding in Making Breeding Decisions

Considering Inbreeding in Making Breeding Decisions. What is inbreeding?. The likelihood that an animal inherits the same gene from each parent because the parents have ancestors in common. Why is inbreeding important?.

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Considering Inbreeding in Making Breeding Decisions

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  1. Considering Inbreeding in Making Breeding Decisions

  2. What is inbreeding? • The likelihood that an animal inherits the same gene from each parent because the parents have ancestors in common

  3. Why is inbreeding important? • The higher the inbreeding, the more likely deleterious recessives will be expressed • Inbreeding depression = the resulting reduction in performance

  4. Inbreeding depression per 1% inbreeding

  5. How inbreeding is used in calculation of PTA’s • Lactation records and relationship matrix are adjusted for inbreeding • Evaluations are adjusted for expected future inbreeding • Expected future inbreeding is half the relationship of the animal to 600 recent cows

  6. Benefits of AIPL procedure • Bull not penalized if daughters are inbred • Bulls docked if they are more highly related to potential mates than average

  7. Ten most highly related Holstein sires to cows in Aug 2005inbreeding coefficient calculated to 1960 base

  8. Limitation of AIPL procedure • PTA is not adjusted for the bull’s relationship to a particular mate

  9. What can be done about inbreeding? • When breeding a cow, use an unrelated sire • Progeny of a highly inbred cow will not be inbred if she and the mating sire have no common ancestors

  10. Is this practical? • Usually, no • Intensive selection has led to rising levels of inbreeding • Popular sires are likely to be related to many cows

  11. Holstein Inbreeding

  12. What are mating programs? • Computer programs that recommend a service sire for a cow • The more pedigree data they have, the better recommendations they can make • Use of a mate that will cause higher inbreeding in the calf is justified if the superiority in PTA exceeds the additional inbreeding depression

  13. Examples of mating programs • Holstein Inbreeding Calculator • Jersey-Mate • Stud programs

  14. Crossbreeding • Mating parents of different breeds • Provides relief from inbreeding • Heterosis – superiority over the average of the parents

  15. Average heterosis value

  16. Crossbreds in genetic evaluations • Methods to include records of crossbreds are being developed • All breeds can be included in the same evaluation • Requires pedigree of crossbreds including parental breed • On farm software may choke on: • Norwegian Red • Montbéliard • Ranking depends on breed of mate

  17. Conclusions • Inbreeding reduces productivity • Semen should be allocated to minimize the inbreeding of progeny • Mating programs can be profitable • Crossbreeding gives heterosis (relief from inbreeding depression) • Genetic evaluations that include crossbreds are coming

  18. Other research at AIPL • Evaluations for: • Stillbirth • Male fertility • Persistency • Disease resistance • Change in PL to credit longer lactations • Detecting abnormal distributions of calving ease scores

  19. Other research at AIPL (Cont) • Parentage verification based on Single Nucleotide Polymorphisms (SNP) • Determine the rate of parentage errors • Using SNP to trace inheritance of chromosomal segments • Potential to greatly increase accuracy of parent average

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