Identifying critical control points for colostrum contamination in first milking colostrum from Scottish dairy herds

Excessive bacterial contamination (≥100,000 colony forming units [CFU]/ml total bacteria count (TBC) and ≥ 10,000 CFU/ml total coliform count [TCC]) reduces the quality of colostrum and subsequent absorption of IgG across neonatal enterocytes, leading to failure to transfer of passive immunity (FTPI). Furthermore, the presence of pathogenic bacteria can cause disease in their own right. The objectives of the study were to identify critical control points and farm risk factors to minimise colostrum contamination from Scottish dairy herds. Eleven farms in Dumfries and Galloway, Scotland, were enrolled and first milking colostrum was sampled at sequential control points throughout the harvest, storage and feeding process. Farmers also completed a questionnaire at enrolment detailing colostrum management practices to identify risk factors for high bacterial contamination. Samples then underwent testing to estimate TBC, TCC and Brix % (measure of total solids estimating IgG concentration). Samples collected directly from cows' teats had a lower median TBC (4000 CFU/ml, IQR = 15,000 CFU/ml) and TCC (1850, CFU/ml, IQR = 3775 CFU/ml) than those collected from storage buckets (median TBC = 101,000 CFU/ml, IQR = 930,000 CFU/ml and median TCC = 12,000, IQR = 108,000 CFU/ml) and feeding equipment (median TBC = 410,000 CFU/ml, IQR 3230,000 CFU/ml; median TCC = 40,000, IQR = 375,000 CFU/ml). Linear regression models revealed higher bacterial contamination was associated with a larger number of buckets used between harvest and storage of colostrum; smaller size of containers used to store colostrum, method of colostrum storage (freezing), and method of teat cleaning (wet wipe). Mean teat, storage bucket and feeder Brix (%) values were 23.1 %, 22 % and 23.1 % respectively. A one-way repeated ANOVA showed no difference in Brix % between source type (F = 2(3168), p = 0.1). Brix % was negatively associated with increasing time from calving to colostrum harvest.