Effect of colostral volume, interval between calving and first milking, and photoperiod on colostral IgG concentrations in dairy cows

Objective To identify cow and management factors associated with colostral IgG concentration in dairy cows. Design-Prospective observational study. Animals 81 multiparous Holstein-Friesian cows from a single herd. Procedures-Serum was obtained at the start of the nonlactating period, and cows were assigned to 1 of 4 photoperiod groups: natural day length (n = 22 cows), long days (16 h of light/d [21]) or short days (8 h of light/d [20]) for the entire nonlactating period, or natural day length followed by short days for the last 21 days of the nonlactating period (18). Serum and colostrum were collected at the first milking after calving. Regression analysis was used to investigate associations between colostral IgG concentration and the interval between calving and first milking, colostral volume, photoperiod, length of the nonlactating period, and season of calving. Results-Colostral IgG concentration decreased by 3.7% during each subsequent hour after calving because of postparturient secretion by the mammary glands. The interval between calving and first milking and the colostral volume were significantly and negatively associated with colostral IgG concentration, with the former effect predominating. Photoperiod had no effect on colostral IgG concentration or volume. Serum protein concentration at calving correlated poorly with colostral IgG concentration. Conclusions and Clinical Relevance-Dairy producers should harvest colostrum as soon as possible after calving to optimize transfer of passive immunity in neonatal calves. Photoperiod can be manipulated without adversely affecting colostral IgG concentration.