New research indicates calves should get colostrum, what their first milk is called, sooner than previously recommended. With spring calving season just around the corner, talking about colostrum in calves is important. Calves are born with basically no immunity to disease and so without colostrum, most of these calves will not survive. Focusing on monitoring the calving process is obviously important but the job of monitoring the birthing process is only half completed. The next part is to make sure the calf gets up and nurses within 4 hours, and it seems a lot of producers don’t worry about this as much as they probably should.
There are two types of immunity: active and passive. Active immunity develops after vaccination or exposure to the organism. The term herd immunity is common these days due to the coronavirus in people, and herd immunity is active immunity. It is impossible for a newborn calf to have active immunity. When the calf is born and nurses, the calf receives immunity through the first milk, which is called passive immunity. Without this immunity it is unlikely a calf will survive for a long period of time. It was previously believed that as long as calves nursed the first milk within 24 hours the antibodies would be transferred, and Dr. Glenn Selk indicates some is transferred at 24 hours but only about 10%. Almost 65% of the antibodies are transferred in the first 6 hours and about 30% by 12 hours. So, if the calf goes through that 6-hour window without nursing, 65% of the antibodies will not be absorbed. The limiting factor is not the antibodies in the milk, but that the gut essentially closes and cannot absorb the antibodies after these time periods. If a calf has not nursed by 4 hours, get the cow up, milk her out and feed the calf.