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Title: RELATION OF BOVINE LEUKOCYTE ADHESION DEFICIENCY AND GENETIC MERIT FOR PERFORMANCE TRAITS

Author
item POWELL, REX
item NORMAN, H
item COWAN, C - GENETIC VISIONS INC

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: The genetic disease bovine leukocyte adhesion deficiency (BLAD) is virtually always fatal if the defective gene is received from both parents. However, animals that have only one of the defective genes are not affected. A DNA test developed in 1991 has allowed the testing of bulls before widespread use and the identification of carriers. Carrier bulls were found to have become relatively frequent; 23% of Holstein bulls sampled in 1989 were carriers. Through testing and culling, no bulls being sampled now are carriers. However, elimination of the BLAD gene might have other, undesirable effects or might limit the rate of genetic progress for performance traits as a result of an association with those traits. An analysis of whether the BLAD gene affected traits evaluated by USDA's Animal Improvement Programs Laboratory (milk, fat, and protein yields; fat and protein percentages; productive life; and somatic cell score) or was linked to genes for those traits showed only a minimal, negative relationship for some traits. Therefore, dairy breeders should feel confident that elimination of the BLAD gene will not impede the rate of genetic improvement for other traits. An improved mechanism for reporting the results of DNA testing for genetic diseases is needed so that breeders will be better informed and research can be more definitive.

Technical Abstract: Existence of pleiotropy or linkage between bovine leukocyte adhesion deficiency and other traits and the impact of removal of the recessive, undesirable allele on genetic progress for those traits had not been examined. Frequency of carriers among 6400 Holstein bulls tested was 8.2%; however, reporting was incomplete and, therefore, the estimate of carrier frequency biased downward. For bulls sampled through artificial insemination, 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 by a model in which daughter yield deviation minus 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 sires; only protein yield for one sire was significantly and negatively related to the recessive allele. Carrier bulls now are labeled, and some continue to be used actively in artificial insemination because of superiority for other traits. Consequential pleiotropy or linkage between the allele and the traits studied is unlikely. Genetic progress for these traits will not be impeded by elimination of the allele.