Growth and metabolism of calves in a dairy cow-calf contact system with gradual weaning and separation.

In cow-calf contact (CCC) systems, calves are allowed to have maternal contact until a later age than in conventional dairy production systems, where cow and calf are separated shortly after birth. Although CCC systems may vary in design, for example, dam-calf rearing versus foster cow rearing, or full CCC versus partial CCC. The main characteristic is that calves in CCC systems are able to suckle for a prolonged period, at least for part of the day, allowing social behaviour between dam and calf. One challenge faced by calves in CCC systems is weaning and separation from the dam or foster cow. Unlike calves separated shortly after birth, CCC calves often experience simultaneous weaning and separation. Weaning is already a stressful event for calves and should be disentangled from other stressors such as separation.

Calf growth is a common measure to attempt to understand the weaning and separation response. While pre-weaning growth of calves with prolonged CCC is greater compared with conventionally reared calves mainly due to their higher milk intake, their post-weaning growth is typically lower shortly after weaning than that of conventionally reared calves of the same age. Lower post-weaning growth in CCC calves is probably due to weaning stress and being less adapted to a solid feed diet when weaned, owing to the high milk intake and the consequent lower pre-weaning solid feed intake compared with conventional calves with restricted milk feeding. In addition, the metabolic and inflammatory status of calves with prolonged CCC may change not only due to differences in weaning and separation response but also in milk intake and calf growth compared with conventionally reared calves. To make sense of these differences, the aim of the study cited was to evaluate growth, and the metabolic and inflammatory status of calves in a dam-calf contact rearing system with gradual weaning and separation in comparison with calves in a conventional rearing system.

In two experimental batches, treatment group allocation was balanced for cow lactation number and breed (Swedish Holstein or Swedish Red) and for calf sex and breed (dairy or beef-on-dairy crossbred). The calves were allowed full contact with dams (FC, n = 21) until the start of a 10-day fence-line weaning with gradually reduced suckling opportunities at average 12.5 weeks of age. Conventionally reared calves with no contact with their dams (NC, n = 22) received 8 L whole milk per day from teat buckets and were first individually housed for one week followed by group housing. The NC calves were gradually weaned over 10 days when 12.2 weeks old. In addition, both FC and NC calves had ad libitum access to concentrates and roughage.

The results showed that pre-weaning growth was greater in FC than NC calves (1.4 vs. 1.1 ± 0.06 kg/day). During the pre-weaning period, serum glucose, insulin, IGF-1, and haptoglobin concentration did not differ between treatment groups, but non-esterified fatty acids (NEFA) concentration was greater in FC than NC calves. After weaning, serum glucose, insulin, and NEFA concentration decreased for both FC and NC calves. Serum IGF-1 concentration decreased after weaning for FC calves but not for NC calves. Post-weaning, the FC calves retained their BW advantage and higher back fat thickness compared with NC calves despite having lower post-weaning growth than NC calves in batch 1 (1.1 ± 0.06 kg/day vs. 1.4 ± 0.06 kg/day) but not in batch 2 (1.1 ± 0.09 kg/day vs. 1.0 ± 0.06 kg/day).

In summary: Full CCC promoted pre-weaning calf growth, with limited effects for metabolic and inflammatory variables measured in the calves of this study. Calves with CCC for at least 12 weeks had a higher BW and BFT compared with conventionally reared calves receiving 8 L milk/day, despite having a lower post-weaning growth and a later start of increase in concentrate intake. Metabolic and inflammatory variables as a measure of adaptive responses to weaning, including serum glucose, insulin, IGF-1, and haptoglobin concentrations, of calves with CCC were similar to conventional calves of the same age, while NEFA concentration was higher in FC calves. Future research should substantiate the effects of extending the fence-line weaning period on stress experienced at weaning and separation in both calves and cows, as well as the long-term effects on body condition, metabolism, and fertility of the calves.