Colostrum contains various bioactive constituents.
First, there are benefits in feeding mom’s colostrum to her calf. Owing to the unique anatomy and physiology of the newborn calf, they can absorb the Ig and immune cells from the dam. These immune or “white blood” cells function by stimulating development of the immune system in the calf at a much earlier age. Unfortunately, this benefit requires consumption of the dam’s fresh colostrum.
Colostrum also contains higher levels of various bioactive constituents which gradually decline reaching lower levels found in milk by the sixth milking. These include oligosaccharides, certain fatty acids, lactoferrin, growth factors (IGF, TGF..), enzymes, microRNAs, and cytokines. It is known that these colostrum constituents have a positive impact on cellular function, growth, and development when fed to calves during the first days of life.
Researchers in Canada compared calves fed similar quantities of first milking pooled colostrum followed by colostrum, a mix of 50% colostrum and 50% whole milk and only whole milk between 12 and 72 hours of age. Maximum serum IgG levels were reached at 13h of age for the whole milk fed calves while IgG levels for the remaining treatments plateaued near 30 h of age indicating continued absorption of Ig. Similarly, the surface area of intestinal tissue for calves receiving colostrum or the mixture was more than 50% greater than calves receiving only whole milk. This likely indicates benefits not only for IgG absorption but also other nutrients which are so critical for the very young calf.