Improving consistency in cow-calf contact studies: the benefits of a protocol for colostrum supply and near ad libitum milk feeding for separated calves

Studies on cow-calf contact (CCC) systems often report better weight gain and sometimes an improved health in calves. However, calves in CCC systems with unrestricted suckling opportunities are often compared to artificially reared calves who are fed a restricted amount of milk. Our study investigated the growth rate and the health status of 41 German Holstein calves during their first nine weeks of life. Calves had either whole-day contact to their dam in the dairy herd (Contact, n = 24) or were artificially reared by providing 16 L d− 1 whole milk (Control, n = 17). The provision of colostrum for all calves followed the same protocol. The Brix level of the colostrum and the transition milk collected during the three first milkings postpartum of all dams was recorded, as well as the Brix level in blood serum of all calves. The occurrence of diarrhea in calves was recorded daily, while health status and weight gain were assessed weekly. The transfer of passive immunity was successful in Control (LSM ± SE: 9.5 ± 0.4% Brix) and Contact calves (8.9 ± 0.3% Brix, P = 0.105). Calf presence did not affect the Brix level of the dam’s colostrum and transition milk. Control calves consumed on average 10.3 ± 2.8 L d− 1 of the offered 16 L milk, suggesting that they were fed near ad libitum. The average daily weight gain did not differ between Control (987 ± 55 g) and Contact calves (1051 ± 46 g, P = 0.319) and increased with calf age. No effect of cow contact on the occurrence of diarrhea, the weekly health status or veterinary treatments in calves was found. Prolonged contact with the calf does not affect the Brix values of the dam’s colostrum or transition milk. Calves that are not separated from their dam after calving do not experience failure of transfer of passive immunity when fed high-quality colostrum from a bottle. When compared to CCC calves during their first months of life, artificially reared calves should be fed at least 16 L d− 1 whole milk.