GENETICS, BREEDING, AND MODELING Relationship of Bovine Leukocyte Adhesion Deficiency with Genetic Merit for Performance Traits

them undesirable and many fatal in the homozygous Examination of the existence of pleiotropy or linkage of bovine leukocyte adhesion deficiency with other traits and of the impact of removal of the recessive, undesirable allele on genetic progress for those traits has been limited. Frequency of carriers among 6400 Holstein bulls tested was 8.2%; however, reporting was incomplete, and, therefore, the estimate of carrier frequency was biased downward. For AI-sampled bulls, carrier frequency reached a high of 23% for bulls sampled during 1989 but declined to 0% since then because of DNA testing and culling. Association of the allele with yield, productive life, and somatic cell score was examined with a model in which the daughter yield deviation minus the mean of parent evaluations was explained by carrier status. A significant negative relationship was found with protein yield when effect of sires was ignored; all associations were unfavorable. Linkage was examined by applying the model for each of four sire families; only protein yield for one sire was significantly and negatively related to the recessive allele. Carrier bulls currently are labeled, and some continue to be used actively in AI because of superiority for other traits. Consequential pleiotropy of the allele or linkage of the locus with the traits studied is unlikely. Genetic progress for these performance traits will not be impeded by