Effects of Partial Cow–Calf Contact and Social Companions on Health, Performance, and Behavior of Calves

Provision of cow–calf contact (CCC) in combination with pair housing may enhance welfare and stimulate greater intake of both milk and starter feed, thereby improving the performance and health of calves reared under cold conditions. This study was conducted to investigate the effects of combining partial daily CCC (5 h/d) with pair housing (19 h/d) in dairy calves reared in outdoor pens during winter, when the mean ambient temperature was 6.2 ± 0.4 °C throughout the study period. A total of 30 Holstein calves (birth weight = 37.4 ± 3.4 kg) were enrolled at birth. Fourteen calves received daily dam contact and were pair-housed (DC-PH), while the remaining 16 calves had no dam contact (NC); of these, 8 were pair-housed (NC-PH) and 8 were individually housed (NC-IH). Dam contact was maintained until day 60, after which all calves were weaned and group-housed until day 80. Milk consumption was greater in DC than NC calves (7.4 vs. 5.5 L/d). During the pre-weaning period, body weight and average daily gain did not differ between treatments. However, DC-PH calves had greater body weight at day 80 and higher average daily gain between days 60 and 80 than NC-PH calves (p = 0.01 and p = 0.02, respectively). Pre-weaning starter feed intake and feed efficiency did not differ across treatment groups. Dry matter digestibility was significantly greater in NC-PH than in NC-IH calves (87.7% vs. 81.4%; p = 0.03), but no significant effects were observed on NDF and DM digestibility between NC-PH and DC-PH calves. On day 54 (the pre-weaning phase), compared with NC-PH calves, DC-PH calves had higher blood glucose (p = 0.05), lower cortisol (p = 0.02), tended to have lower βHBA concentrations (p = 0.06), and a greater ruminal protozoal count on day 35 (p = 0.01). Total health score tended to be higher in DC-PH than NC-PH calves (p = 0.06) and was higher in NC-IH than in NC-PH calves (p = 0.05). During an 8-h behavioral recording prior to weaning, DC-PH calves were observed less frequently performing non-nutritive oral behaviors, such as licking the stall or fences and sucking on other calves, and tended to be more frequently standing, contacting other calves, playing alone, walking, and ruminating than NC-PH calves. After weaning, DC-PH calves were observed more frequently eating, resting, walking, and engaging in social interactions than NC-PH calves. Likewise, after weaning, NC-IH calves were observed more frequently playing, vocalizing, and walking, but less eating than NC-PH calves. Overall, our findings indicated that while social interaction (NC-IH vs. NC-PH) significantly improved dry matter digestibility and health, the addition of dam contact (DC-PH) maintained nutrient digestibility at levels comparable to NC-PH, but tended to reduce health status. Also, calves in the DC-PH treatment, which voluntarily consumed more milk than NC calves, exhibited greater post-weaning growth, more favorable behavioral responses, and improved pre-weaning metabolic profiles (lower cortisol and βHBA concentrations and higher blood glucose). These findings indicate that the partial dam contact management system, together with greater voluntary milk intake, was associated with enhanced post-weaning performance and metabolic status, as well as differences in rumen microbial development. However, as milk intake was not standardized across treatments, these responses cannot be attributed solely to maternal contact. Overall, under the conditions of this study, partial dam contact represents a feasible management strategy to support calf welfare and development, provided that appropriate environmental management is implemented to minimize disease risks.