Field investigations on colostrum composition and serum thyroxine, cortisol and immunoglobulin in naturally suckled dairy calves

The relationship between the composition of serum from newborn sucking calves and colostrum from their dams was investigated to obtain more information about factors affecting the colostral transfer of immunity. There was a significant correlation between initial percentage dry weight of colostrum and calf serum immunoglobulin (Ig) concentration at 24 h. There were no correlations between cow serum thyroxine (T4), calf serum T4 and calf serum Ig. There was a negative correlation between calf serum cortisol and Ig but this may have been due to serum cortisol being affected by haemodilution after sucking. The normal rapid decline in serum cortisol in newborn calves was delayed by injecting ACTH. Colostral transfer of immunity as measured by serum Ig at 12 and 24 h was significantly greater in ACTH treated calves than in untreated calves. A multiple analysis of variance of data from several hundred calvings on one farm showed that the transfer of colostral immunity was related to place of calving, calving number, udder shape, dam and sire. Colostral transfer of immunity was lower in calves born indoors in winter than in those born outdoors in summer. It was also low in calves from first calf heifers, from cows with pendulous udders, from cows with a history of poor colostral transfer and in calves sired by certain bulls.