Évaluation de la variabilité du transfert d’immunité passive dans les troupeaux laitiers du Québec
Calves are born almost agammaglobulinemic, so they must ingest immunoglobulins from their mother's colostrum; it’s the transfer of passive immunity (TPI). An adequate TPI reduces the risk of mortality and morbidity during the first weeks of life. A high percentage of success of TPI in herds maximizes the chances of having a herd with healthy calves. The objectives of this herd-level study were to quantify the prevalence of adequate TPI, and to investigate its association with colostrum management. A total of 59 Quebec commercial dairy herds were selected by convenience to participate to this observational study. In every participating herd, a minimum of 14 blood samples from Holstein calves were sampled to estimate their prevalence of adequate TPI using a digital Brix refractometer. Samples of colostrum served to each of these calves were collected to evaluate immunological quality using a digital Brix refractometer and bacteriological quality using Petrifilm systems. A questionnaire on colostrum management practices was completed by dairy producers to assess on-farm practices. The herd-level prevalence of adequate TPI (defined as the percentage of calf with serum Brix degree ≥ 8.4%) success ranged from 24% to 100%, and the median was 67%. In the multivariable linear regression models, the prevalence of adequate TPI was associated with the prevalence of adequate volume (defined as the percentage of calves receiving ≥ 2 liters of colostrum at first meal), prevalence of adequate colostrum quality (defined as the percentage of calves receiving a colostrum with ≥ 20,9 Brix degrees), and prevalence of adequate time to the first meal (defined as the percentage of calves receiving colostrum within ≤3h after birth), but was not associated with the gender or bacterial contamination prevalence. In summary, the prevalence of success of TPI varied greatly and was influenced by management practices of dairy farmers.
Colostrum Bacteriological quality Immunological quality Passive immunity transfer Dairy herd Brix refractometer