Impact of 2 versus 1 colostrum meals on failure of transfer of passive immunity, pre-weaning morbidity and mortality, and performance of dairy calves in a large dairy herd

Failure of transfer of passive immunity (FTPI) due to inadequate ingestion of colostral immunoglobulins by neonatal calves is associated with increased mortality and morbidity risks. Feeding a sufficient amount of quality-tested colostrum within the first hours of life is essential for successfully transferring passive immunity. Many farms have implemented giving calves a second meal of colostrum a few hours after an initial feeding given soon after birth to maximize the opportunities for passive immunity transfer. However, excellent passive immunity can be achieved with a single feeding of sufficient quality-tested colostrum. Moreover, there is currently no evidence demonstrating the impact of a second colostrum feeding within 24 h of life in calves receiving adequate volumes of quality-tested colostrum in a single feeding. Hence, the objective of this retrospective cohort study was to compare the risks of FPTI, pre-weaning morbidity and mortality, and growth and performance between dairy calves that received two feedings of colostrum and those that only received one feeding after birth. For this, the health and production records of a large dairy herd were analyzed. At this farm, newborn calves receive 3 L of quality-tested colostrum soon after birth followed by another 2 L 5-6 h later. However, at times of shortages of colostrum, calves only receive the initial 3 L meal. The records of 2,064 male and 2,272 female calves over a period of 3 years were analyzed, where 4,156 and 180 calves received 2 and 1 meal of, respectively. Data from both sexes were included in the analysis of the risks of FTPI, morbidity, and mortality; however, only data from heifer calves were utilized for growth and performance analysis. Survival analysis was used to estimate the association of a second colostrum feeding with pre-weaning morbidity and mortality, age at first insemination, and age at first calving. Logistic regression was used to investigate the association of a second colostrum feeding with FTPI. A generalized linear model was used to investigate the impact of receiving 2 feedings of colostrum on the number of inseminations received by heifers. Linear regression models were used to assess the association between the number of colostrum feedings and pre-weaning average daily gain (ADG) and first lactation 305-d Mature Equivalent milk production (305ME). Calves that received two feedings of colostrum had lower odds of FTPI, a lower probability of being treated for respiratory disease, diarrhea, or any disease, and a greater pre-weaning ADG. However, there was no association between the number of colostrum feedings and pre-weaning mortality or the probability of first insemination or first calving, although heifers receiving two colostrum feedings tended to receive fewer inseminations and to have a greater first lactation 305ME. Collectively, our results suggest that feeding calves a second feeding of colostrum 5-6 h after the initial feeding soon after birth could be an effective strategy to decrease FTPI and morbidity and optimize ADG in dairy calves pre-weaning. Future multi-herd randomized trials are needed to confirm the positive impact of a second meal of colostrum in dairy calf health observed in this study.