Alterations in chemical composition of colostrum in relationship to post-parturn time

Experiments were designed to study the alterations in colostrum composition in relationship to post-partum time in dairy cows differing in milk yield. Two groups of 5 cows each, with high or low milk yield, respectively were used. Colostrum samples were collected on day 1 and day 3 after birth. Concentration of the major colostrum constituents (milk protein, lactose, dry matter and solid non-fat extract) changed significantly after birth, the levels on day 3 being similar to those of mature milk. The most significant changes were those in the concentration of milk protein, that on day 3 was more than twice lower as compared to the first portion of colostrum. There was no effect of milk secretion intensity on chemical composition of colostrum.