Colostrum Loses Value with Increased Time after Calving
The acquisition of adequate immunity by newborn calves is the most important factor affecting their resistance to disease as neonates. We know that the amount of colostrum consumed, the time from calving to colostrum ingestion, the antibody content of the colostrum and the vigour of the calf all affect the final immune status of the calf. Recent research points out that the timing of colostrum collection from the cow is also very important.
Colostrum samples collected at 2, 6, 10 and 14 hours post-calving from 13 cows were measured for IgG concentration. The samples collected at 6, 10 and 14 hours after calving had significantly lower mean IgG concentrations than did those collected at 2 hours. Colostral IgG concentrations were 113, 94, 82 and 76 g/L at 2, 6, 10 and 14 hours post-calving respectively.
The loss of colostral IgG has not been explained. Each quarter of each cow had a 10 mL sample removed for testing and each quarter was sampled at only one of the four sampling times. Following sampling, each quarter was completely milked out to determine the total weight of colostrum present in the quarter at the time of sample collection. As the weight of the colostrum in each quarter did not vary, the authors suggest that it is unlikely that dilution from additional milk production was the reason for the lower IgG concentrations over time. They suggest that the antibodies may be passively resorbed into the cow's circulation over time.
On some farms a cow's colostrum is not used to feed her own calf. Rather, frozen colostrum from another cow may be used, and the cow's own colostrum collected at a more convenient first milking time. On some farms there may be an inclination to leave this first milking until a time when milking equipment is turned on to milk the other cows. Hours could elapse until a cow is first milked. The current research points out that using only the colostrum collected within the first two hours after calving for the first feedings for a newborn calf will help to increase the amounts of IgG delivered.
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