Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 3, 2006
Publication Date: July 1, 2006
Citation: Van Raden, P.M., Miller, R.H. 2006. Effects of non-additive genetic interactions, inbreeding, and recessive defects on embryo and fetal loss by 70 days. Journal of Dairy Science. 89(7):2716-2121. Interpretive Summary: Additive, dominance and inbreeding effects on 70 d nonreturn rates were estimated using 1,739,055 first inseminations of Holsteins. Heritability was 1%, dominance variance was 2.8%, and regression of nonreturn rate on inbreeding of embryo was -.096 per 1% increase in inbreeding. Neither CVM nor DUMPS carrier status were significant effects on 70 d nonreturn rate. Crossbreeding and inbreeding minimization strategies reduce probability of both mates being carriers of the same defect and thus increase fertility.
Technical Abstract: Lethal recessive genes that cause early embryo loss are difficult to detect because they may appear to be failed inseminations or missed heats. Nonreturn rate at 70 d after first insemination (NR) was evaluated as a trait of the embryo from 1,739,055 first services using a non-additive genetic model. Effects modeled included herd-year-season, parity of cow, sire of cow, service bull, interaction of service bull with sire of cow, and regression on inbreeding of embryo. Simultaneous solutions for all effects were not possible; thus, main effect variances were estimated using REML, and those effects were removed from the data. Interaction variance was estimated from the residuals using the tilde-hat approximation to REML. Service bull effects were assumed to be constant across time and unrelated. An additive relationship matrix was used for sire of cow and a dominance relationship matrix for the interaction term. Data included observations from January 1995 through August 2001 and represented 1,251 Holstein service bulls and sires of cows. For each 1% increase in inbreeding, NR declined by an estimated 0.096. A regression of this size could be explained by >20% of animals carrying defects that cause early embryo loss. Of the total variance, service bull contributed 0.36%; sire of cow, 0.24% (heritability of 1.0%); and interaction, 0.18% (dominance variance of 2.8%). Number of records per interaction averaged only 6 but with a maximum of 2,077, and 50 bull pairs had >500 records, which resulted in reliabilities of >50% for their interactions. Predicted interactions that included effects of inbreeding ranged from -3.6 to +2.9, compared to the mean NR of 56%. The poorest interactions were not caused by known recessive defects. Complex vertebral malformation (CVM) generally causes loss of pregnancies later in gestation, and few current bulls carry the gene for deficiency of uridine monophosphate synthase (DUMPS). Further study of the families with poorest interactions could uncover new recessive defects.