The influence of social networks on welfare and productivity in dairy cattle

Abstract

Cattle are gregarious animals that form stable social groups based on affiliative and dominance relationships. However the husbandry practices of the modern dairy industry typically do not take social relationships into consideration, despite a growing body of evidence demonstrating important effects of social relationships on health and fitness in wild animals. Keeping cattle in large, unstable groups can lead to reduced welfare and productivity due to social stress and further research is needed to provide a beneficial social environment that can instead provide stress buffering effects. Social network analysis (SNA) is becoming an increasingly popular method to study animal social groups but until very recently has not been applied in animal welfare studies, where it can offer great advantages. This thesis uses SNA to investigate the social structure of a dynamic group of dairy cattle, and to explore the connection between social network position, and health and productivity. Social data was collected using spatial proximity loggers, allowing remote, continuous recording of associations between cattle. This approach was also used to measure relationships between young calves, investigating the effects of the early social environment. First, proximity loggers were tested and found to exhibit a significant sampling bias, which had consequences for SNA; a correction method was developed to improve their robustness. The social network structure of 110 lactating dairy cows on a commercial farm was then quantified, over four one-month periods. The network was highly centralised and social stability was low, however there were heterogeneous relationships between cows and we found evidence for assortment by traits. Social network position was linked to the health and productivity of cows; more gregarious individuals had higher milk yields and higher somatic cell counts which may represent a cost-benefit trade-off. Another study assessed the effects of pair-housing calves on weaning stress, health and production during pen rearing. Calves that were paired with a social companion showed a lower stress response to weaning than those housed individually. This effect was further reduced for calves paired earlier, suggesting that social bond strength is important for social support in cattle. The social networks of calves when grouped together showed some stability and relationships were heterogeneous, with social associations being influenced by prior familiarity. Advancing our understanding of the social requirements of dairy cattle is fundamental for their welfare, and for productivity, and is particularly important in light of recent farming intensification.