FREQUENCIES AND EFFECTS OF ALTERNATIVE DRB3.2 ALLELES OF BOVINE LYMPHOCYTE ANTIGEN FOR HOLSTEINS IN MILK SELECTION AND CONTROL LINES

Frequencies of alleles at the DRB3.2 locus of the bovine major histoco mpatibility complex for two genetic lines of Holsteins were compared, and allelic effects on yield and udder health traits were examined. Th e DRB3.2 genotypes of 186 cows and heifers were determined using DNA t hat had been extracted from blood samples. The cattle were from a desi gned selection experiment for milk yield. After edits, 173 cows and he ifers with known alleles remained (54 from a control line and 119 from a selection line for milk yield). A total of 19 alternative DRB3.2 al leles appeared across the two lines, and frequencies ranged from 0.3 t o 21.4%. Allelic frequencies differed significantly between the select ion and control lines. Alleles 3, 8, 9, 10, 26, and 28 were more frequ ent in the control line, but alleles 16, 24, and 27 were more frequent in the selection line. An animal model was used to estimate gene subs titution effects of alternative alleles on milk yield, fat yield, and protein yield, SCS, chronically elevated SCS, acutely elevated SCS, an d mastitis incidence. First, second, and third lactations were analyze d separately. Allele 7 was associated with a significant increase in p rotein yield during first and second lactations and a significant incr ease in chronically elevated SCS and acutely elevated SCS during secon d lactation. Because of conflicting results with other studies and a l imited numbers of cows, additional research is needed before specific alleles are confirmed to be associated with measures of yield and udde r health.