Effect of colostrum immunoglobulin concentration on early growth performance in dairy heifers.

The study was conducted on the farms "Aiteke Bi-SK" and "Kedr", which maintain some of the best dairy cattle herds in Kazakhstan. According to the results, the qualitative parameters of colostrum from cows in the experimental group were superior to those of the control group, particularly in fat content. For example, in "Aiteke Bi-SK", the difference in fat content reached 1.38% (P<0.001), and in "Kedr" - 1.34% (P<0.001). Feeding newborn calves with colostrum rich in immunoglobulins led to an increase in body weight by 2.1 kg (P<0.001) on day 10 of life in the first farm compared to the control group and by 2.0 kg (P<0.001) in the second farm. The magnitude of treatment effect was large (Cohen's d≥2.0), indicating strong biological relevance of colostrum immunoglobulin concentration on early growth. It was found that the absolute, average daily, and relative growth rate between the experimental and control heifers differed by 1.8-1.9 kg (P<0.01), 180-190 g/day (P<0.05) and 4.8-5.0% (P<0.001), respectively.