A herd-level study on colostrum management factors associated with the prevalence of adequate transfer of passive immunity in Québec dairy herds

The objective of this study was to identify herd-level colostrum management factors associated with the adequate transfer passive immunity (TPI; defined as serum Brix refractance ≥8.4% in first week life). A total 59 commercial Holstein dairy farms were included observational cross-sectional study. In every participating herd, a minimum 14 calves sampled measure their TPI using digital refractometer. Colostrum samples fed each these collected estimate IgG concentration (colostrum quality) refractometer and bacterial contamination Petrifilm (3M, St. Paul, MN) culture system. Dairy producers completed questionnaire on assess on-farm practices. outcome prevalence calculated based proportion (defined an individual threshold Brix) tested within herd. According determined previous investigating influencing achieve at calf level, volume meal (≥2.5 L), quality (≥24.5% Brix), time feeding (delay between birth meal, ≤3 h), low aerobic (≤20,000 cfu/mL), coliform (≤1,000 females calculated. ranged from 24% 100%, median 68%. herd prevalences quality, feeding, contamination, females, 71, 42, 41, 64, 88, 61%, respectively. final model, feeding. summary, practices varied greatly influenced TPI.