As cattle ranchers, we focus on preventing illnesses in our calves. Even right after birth, there is a series of events that need to occur in order to keep calves healthy all the way through their lives. The most important event is when the calf consumes the cow’s first milk, called colostrum.
Calves are born with a weak, naive immune system. To help with this, their mother’s colostrum contains antibodies that help ward off infections. As long as the calf consumes this colostrum within the first 24 hours after birth (though it is prefered that it comes within the first two hours), the needed antibodies can cross the gut wall and circulate in its bloodstream. This is called “passive transfer”, since the immunity is being given to the calf from its mother, rather than the calf making its own immunity. If this system fails, it is considered to be Failure of Passive Transfer (FPT).
If we are unsure if a calf has failure of passive transfer or not, we can run a test to help answer that question. What we do is take a little blood from the calf, then put that blood in a tiny tube called a capillary tube. This blood is then spun in a centrifuge to separate the red blood cells from the serum. The serum is then placed on an instrument called a refractometer, which we can use to measure the amount of solids in the serum. Since the antibodies would add to the solids, if the calf has a level of 5.5 mg/dl of solids or more, it has received enough colostrum. Otherwise, it has failure of passive transfer.
Since there is nothing we can do once a calf has had failure of passive transfer, our main focus is to intervene soon after birth. If a herd is having passive transfer issues, colostrum is supplemented. This is especially the case on calves that are likely to have issues, such as those with a difficult birth or have a mother with little colostrum. With a little TLC, we can get these calves on the right path and keep them healthy!