Interpretive Summary: Temporal kinetics of bovine mammary IgG secretion into colostrum and transition milk
By: Caitlin Vonderohe
Calves are born immunologically naïve, and therefore need to consume colostrum soon after birth to achieve a transfer of passive immunity. The timing, level and degree of immunoglobulin transfer necessary to achieve sufficient immunocompetence in the neonatal calf have been points of contention in veterinary medicine and animal science literature. Although the mainstream recommendation for colostrum intake is to feed at least 200 grams of IgG, but recent work has shown that this recommendation may not be sufficient and may result in failure of passive transfer. Additionally, there has been limited focus on immunoglobulin levels in transition milk. Schalich et al. recently published “Temporal kinetics of bovine mammary IgG secretion into colostrum and transition milk” in the Journal of Animal Science, which assessed the components of transition milk and early postpartum mammary IgG kinetics.
Historically, methods to assess colostrum quality, such as Brix refractometry and ELISA, have been used due to their simplicity and repeatability rather than precision. However, in this study, the authors found no statistical relationship between Brix refractometry reading and a highly precise fluorescent Western blot for IgG, demonstrating the inaccuracy of Brix readings to assess colostrum quality. This disassociation between Brix readings and actual IgG is likely due to confounding levels of glucose and lactose, among other solutes commonly found in colostrum and transition milk. Additionally, contrary to previous belief, 75% of the postpartum mammary IgG is in transition milk, whereas colostrum contained 25% of the total IgG. The volume of colostrum production is also cow-specific, and far more dependent on factors surrounding parturition and stress than parity. Overall, these authors debunked many commonly held beliefs about IgG in colostrum and transition milk; there are many opportunities to apply these findings to calf production.