Use of proximity loggers to Estimate Affiliative and Agonistic Relationships among Group-housed Holstein calves.

We used proximity loggers to map the social network of 15 group-housed suckling Holstein calves over a 70-day period divided into five trial periods. Tag ID, encountered tag ID, and encounter start time and length were collected from the proximity loggers. Use of 3D matrices and trendlines distinguished three encounter types: "rapid decline" (up to ~ 120 s), "moderate decline" (~120 to ~ 600 s), and "exponential decline" (longer than ~ 600 s). We hypothesized that a random encounter between two calves with an agonistic relationship would terminate quickly, whereas affiliative encounters would linger. Quadratic assignment with 5000 random permutations revealed a significant negative correlation between short encounters ("agonistic") and long encounters ("affiliative") matrices in periods 1 and 5 (r = -0.490 and -0.767, respectively), tendency toward negative correlation in period 3 (r = -0.141, p = 0.104), and no significant correlations in periods 2 and 4. These results were in accordance with the social network analyses revealing agonistic (short encounters) relationships in those periods. We suggest using this method in further studies on the effects of various factors on social network dynamics and its effect on health, intake, growth, and efficiency.