Invited review: Social housing of dairy calves—Management factors affecting calf behavior, performance, and health; A systematic review

Abstract

Given increasing adoption of social housing for preweaning dairy calves, we conducted a systematic review to summarize existing literature describing effects of social housing management factors on behavior, performance, and health of dairy calves. Included articles addressed interventions applied to preweaning, socially housed dairy calves, encompassing age at introduction to social housing, group composition (size, stocking density, within-group age range, stability), and housing environment (space allowance, enrichment provision). Outcome measures addressed behavior, including social behavior, locomotor behavior, feeding behavior, abnormal oral behavior, and behavioral responses during tests; performance, including body measurements and weight gain; and health, including clinical health scores and mortality rate. We conducted searches initially targeting any study where dairy calves were housed socially, using Web of Science and PubMed, and subsequently identified a total of 46 relevant studies. Studies investigating age at introduction to pairs or small social groups of 3 to 7 calves (8 experimental studies) suggested possible behavioral and performance benefits, with no negative effects, of earlier introduction to small groups. Earlier introduction to larger groups (assessed in 6 experimental studies and 4 cross-sectional studies) appeared to increase latency to use an automated milk feeder with short-term negative effects on milk intake, yet no evidence of growth effects and variable health effects. Studies investigating effects of group size (assessed in 8 experimental studies and 6 cross-sectional studies) suggested that small social groups may facilitate increased feeding time, with neutral or positive effects on growth and health. Other aspects of group composition, including within-group age range, group stability, and feeder stocking density, were assessed in few experimental studies (7 total), with some results suggesting behavioral benefits of reducing competition for feed and maintaining stable groups. Experimental and cross-sectional studies yielded conflicting findings with respect to health effects of group composition, but results generally suggested possible health risks associated with larger group sizes and within-group age ranges, management factors consistent with the use of dynamic groups. Increasing space allowance (assessed in 6 experimental studies and 6 cross-sectional studies) increased locomotor activity/play behavior and had neutral or positive health effects. Provision of enrichment items (e.g., brushes, combinations of items for oral manipulation; assessed in 5 studies) was found to reduce cross-sucking. Overall, this review describes varied dairy calf social housing management practices which have implications for behavior, performance, and health. Further work is needed to address gaps in knowledge, including long-term effects and variability at the individual and group level, and to establish the external validity of these findings in commercial settings.