Use of mammary gland and colostral characteristics for prediction of colostral IgG₁ concentration and intramammary infection in Holstein cows

Objective - To determine whether mammary gland or colostral characteristics at calving could be used to predict colostral immunoglobulin G₁ (IgG₁) concentration or intramammary infection (IMI) and whether leakage of colostrum affects IgG₁ concentration. Design - Prospective study. Animals - 113 multiparous Holstein cows. Procedure - Cows were examined within 3 hours of calving, and mammary gland and colostral characteristics, colostral volume, somatic cell count, and concentrations of IgG₁, fat, and protein were determined. Bacteriologic culture of mammary secretions was performed approximately 14 and 7 days before calving and at calving. Associations of gland and colostral characteristics with colostral IgG₁ concentration, colostral volume, and IMI were examined. Results - Thick or thin colostrum had higher IgG₁ concentration than colostrum of intermediate viscosity. Colostrum from mammary glands that were firm had low IgG₁ concentration. Colostral IgG₁ concentration was weakly correlated with volume. Intramammary infection was likely to be detected if colostrum contained clots or blood or if the California Mastitis Test (CMT) score was ≥ 2. Somatic cell count was higher for glands with IMI than for uninfected glands, and CMT score was correlated with cell count. Clinical Implications - Mammary gland and colostral characteristics were of little value in predicting IgG₁ concentration. Our findings do not support recommendations that first milking colostrum that is thin (watery) or that is from cows producing large volumes not be fed to dairy calves. Colostral characteristics, particularly CMT score, were of value for predicting IMI.