Summary
In Somerset, United Kingdom, calves were separated from their mothers after calving, reflecting a common operating procedure, and randomly placed into one of three living conditions on day five: individually housed from day five, pair housed from day five, or pair housing beginning on day 28 onward. The researchers measured “health and production” (i.e., growth rate and concentrate intakes), weaning stress, and the social networks of the calves when grouped together (from day 55 onward).
The most effective social buffering occurred with paired calves at five days old, with pairing at 28 days less effective. The number of vocalizations (as a measure of stress) were greatest after the weaning period, with individually-housed calves vocalizing more than pair-housed calves post-weaning. Strengths of the study are the randomization of calves to the various housing systems and the naturalistic setting (i.e., using a commercial farm). A limitation, noted by the authors, is that calves’ social network structure was only observed for their first month of life, while differences in social structure may occur later. According to the authors, the dairy industry must consider social relationships among calves as an essential factor to minimize stress and improve welfare.
The early social environment can influence the health and behaviour of animals, with effects lasting into adulthood. In Europe, around 60% of dairy calves are reared individually during their first eight weeks of life, while others may be housed in pairs or small groups. This study assessed the effects of varying degrees of social contact on weaning stress, health and production during pen rearing, and on the social networks that calves later formed when grouped. Forty female Holstein-Friesian calves were allocated to one of three treatments: individually housed (I, n = 8), pair-housed from day five (P5, n = 8 pairs), and pair-housed from day 28 (P28, n = 8 pairs). From day 48, calves were weaned by gradual reduction of milk over three days, and vocalisations were recorded as a measure of stress for three days before, during and after weaning. Health and production (growth rate and concentrate intakes) were not affected by treatment during the weaning period or over the whole study. Vocalisations were highest post-weaning, and were significantly higher in I calves than pair-reared calves. Furthermore, P28 calves vocalised significantly more than P5 calves. The social network of calves was measured for one month after all calves were grouped in a barn, using association data from spatial proximity loggers. We tested for week-week stability, social differentiation and assortment in the calf network. Additionally, we tested for treatment differences in: coefficient of variation (CV) in association strength, percentage of time spent with ex-penmate (P5 and P28 calves only) and weighted degree centrality (the sum of the strength of an individual’s associations). The network was relatively stable from weeks one to four and was significantly differentiated, with individuals assorting based on prior familiarity. P5 calves had significantly higher CV in association strength than I calves in week one (indicating more heterogeneous social associations) but there were no significant treatment differences in week four. The mean percentage of time that individuals spent with their ex-penmate after regrouping decreased from weeks 1–4, though treatment did not affect this. There were also no significant differences in weighted degree centrality between calves in each rearing treatment. These results suggest that early pair-rearing can allow calves the stress buffering benefits of social support (and that this is more effective when calves are paired earlier) without compromising health or production, and sheds light on the early development of social behaviour in cattle.