George R. Wiggans Animal Improvement Programs Laboratory Agricultural Research Service, USDA, Beltsville, MD Considering Inbreeding in Making Breeding Decisions
CONSIDERING INBREEDING (2)G. R. Wiggans What is inbreeding? The likelihood that an animal inherits the same gene from each parent because the parents have ancestors in common
CONSIDERING INBREEDING (3)G. R. Wiggans Why is inbreeding important? The higher the inbreeding, the more likely deleterious recessives will be expressed Inbreeding depression = the resulting reduction in performance
CONSIDERING INBREEDING (4)G. R. Wiggans Inbreeding depression per 1% inbreeding Milk-65.3lbDPR-0.078% Fat-2.37lbSCS+0.003score Protein-2.14lbPL-0.2mo
CONSIDERING INBREEDING (5)G. R. Wiggans 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
CONSIDERING INBREEDING (6)G. R. Wiggans Benefits of AIPL procedure Bull not penalized if daughters are inbred Bulls docked if they are more highly related to potential mates than average
CONSIDERING INBREEDING (7)G. R. Wiggans Ten most highly related Holstein sires to cows in Aug 2005 inbreeding coefficient calculated to 1960 base NameBYRBull FPast FExp. F TO-MAR BLACKSTAR-ET ROUND OAK RAG APPLE ELEVATION PAWNEE FARM ARLINDA CHIEF MJR BLACKSTAR EMORY-ET WA-DEL RC MATT-ET CAL-CLARK BOARD CHAIRMAN KED JUROR-ET S-W-D VALIANT RICECREST EMERSON-ET WALKWAY CHIEF MARK
CONSIDERING INBREEDING (8)G. R. Wiggans Limitation of AIPL procedure PTA is not adjusted for the bull’s relationship to a particular mate
CONSIDERING INBREEDING (9)G. R. Wiggans 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
CONSIDERING INBREEDING (10)G. R. Wiggans Is this practical? Usually, no Intensive selection has led to rising levels of inbreeding Popular sires are likely to be related to many cows
CONSIDERING INBREEDING (11)G. R. Wiggans Holstein Inbreeding
CONSIDERING INBREEDING (12)G. R. Wiggans 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
CONSIDERING INBREEDING (13)G. R. Wiggans Examples of mating programs Holstein Inbreeding Calculator Jersey-Mate Stud programs
CONSIDERING INBREEDING (14)G. R. Wiggans Crossbreeding Mating parents of different breeds Provides relief from inbreeding Heterosis – superiority over the average of the parents
CONSIDERING INBREEDING (15)G. R. Wiggans Average heterosis value Milk+700lbDPR+1.8% Fat+35lbSCS+0.02score Protein+26lbPL+0.3mo
CONSIDERING INBREEDING (16)G. R. Wiggans 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
CONSIDERING INBREEDING (17)G. R. Wiggans 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
CONSIDERING INBREEDING (18)G. R. Wiggans 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
CONSIDERING INBREEDING (19)G. R. Wiggans 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