The development of large-scale intensive dairy farms led to increased numbers of animals housed indoors. This can lead to competition, with dominance hierarchies determining who gets preferential access to resources. It is therefore important to understand social ranking in farm animals, but there is currently limited data in pre-weaned calves due in part to difficulties in gathering data on agonistic interactions. Here we aimed to automatically detect displacements at the feeder and determine the dominance hierarchy in pre-weaned calves. We used automatic milk feeders to collect data on feeding behavior in an automated way. We then used the information on visits to the feeder to develop an algorithm that detects displacements and used this to compute the Elo-rating, which indicates dominance ranking. Using a 40s threshold between one calf exiting the feeder and another entering, we were able to detect displacements with high performance. The stability of the Elo-rating derived from the displacements (divided in long- and short-term) was high, indicating that a hierarchy is established even in pre-weaned calves. We tested the effects of age and disease on the Elo-rating and showed that older calves were significantly more dominant, while calves significantly decreased in their rank when sick. We then tested for associations between dominance and several behaviors detected using the automatic feeder and location sensors. We demonstrated differences in feeding behavior based on the dominance ranking of calves but there were no effects on movement or affiliative social behaviors. These results show that automatically collected feeding data can be useful for displacement detection and the calculation of dominance hierarchies in young calves, which had previously never been done. This enables the long-term monitoring of dominance of large numbers of calves and could potentially be applied to all farms with automated feeding systems to understand social dynamics between animals.
Keywords: agonistic behavior; calf; precision livestock technology; social dominance.
The Authors. Published by Elsevier Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).