A calf is born with a naïve immune system. The placenta of the cow does not allow immunoglobulins to pass through the maternal blood to the fetus. A newly born calf will not be able to respond to a pathogen the same way an older calf with a more mature immune system would, and is likely to become sick. Colostrum gives the calf passive immunity from its mother, and when it is about three weeks of age, it will start to develop its own immune system.
Colostrum is higher in total solids and protein compared to regular milk.
