|CHITKO MCKOWN, CAROL|
Submitted to: Mammalian Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 29, 2003
Publication Date: March 1, 2004
Citation: Clawson, M.L., Heaton, M.P., Chitko Mckown, C.G., Fox, J.M., Smith, T.P., Snelling, W.M., Keele, J.W., Laegreid, W.W. 2004. Beta-2-microglobulin haplotypes in u.s. beef cattle and association with failure of passive transfer in newborn calves. Mammalian Genome. 2004. V. 15. P. 227-236. Interpretive Summary: Failure of passive transfer (FPT) is a serious condition in which newborn calves do not acquire adequate levels of antibodies from their mother. Calves obtain maternal antibodies solely from colostrum within the first 24 hours of life. The maternal antibodies provide calves with immunological protection while their own underdeveloped immunity matures. Those afflicted with FPT are at risk for infection by opportunistic pathogens and death. This study tested for a genetic association of FPT in newborn calves. The ß2-microglobulin (ß2M) gene codes for a portion of an antibody transporter and was selected as a candidate gene in this study. DNA variation of (ß2M) was identified in U.S. beef cattle. One particular variant of ß2M detected in calves correlated with FPT. Thus, a new genetic risk factor for FPT has been identified. This marker may be used to predict the likelihood of FPT prevalence in cattle breeding programs, and may facilitate the reduction of infectious diseases in beef cattle.
Technical Abstract: Failure of passive transfer (FPT) is a condition in which neonates do not acquire protective serum levels of maternal antibodies. A principal component of antibody transport is the neonatal receptor for the Fc portion of immunoglobulin, a heterodimer of a MHC Class 1 alpha-chain homolog (FCGRT) and beta-2-microglobulin (ß2M). Previously, two FCGRT haplotypes were associated with differences in immunoglobulin G (IgG) passive transfer in cattle. The present study had two objectives: first, to characterize the ß2M haplotype structure in a diverse group of U.S. beef cattle, and second, to evaluate those haplotypes for association with either high or low serum IgG levels in newborn calves. Twelve single nucleotide polymorphisms (SNPs) assorting into eight haplotypes were identified by sequencing regions of ß2M exons II and IV in a multi-breed panel of 96 beef cattle. Calves homozygous for one of the eight haplotypes (ß2M 2,2) were at increased risk of FPT (odds ratio = 10.73, CI95% 2.11-54.48, p = 0.004). These results indicate that this haplotype is in linkage disequilibrium with genetic risk factors affecting passive transfer of IgG in beef calves, an important determinant of neonatal calf morbidity and mortality.