UBC Theses and Dissertations
Agonistic interactions in dairy cattle Krahn, Joseph
Cattle are gregarious animals that sometimes engage in agonistic interactions and are able to form social relationships, including dominance. The aim of this thesis was to address some of the inconsistencies and gaps in the conceptual understanding of agonistic behaviour and dominance in dairy cattle, methods of data collection, and methods of assessing dominance. I outline that dominance is multidimensional and can be influenced by individual characteristics and other factors, including motivation to access resources. I provide guidelines for a more robust approach to estimating dominance in cattle, including a minimum number of observations required and advantages and challenges associated with different methods. Similarly, while group sizes vary on farms, little is known about how this variation effects agonistic behaviour. I hypothesized that cows would engage in fewer agonistic interactions at the feeder when housed in larger groups. I predicted that the majority of agonistic interactions within dyads would be won by the same individual (i.e., directionality) regardless of group size. I tested these predictions using 4 replicates of 50 cows first housed in groups of 50 which were then divided into 5 groups of 10, maintaining the same stocking density of animals to resources. I used a validated algorithm to determine agonistic interactions, which were used to calculate individual Elo-Ratings (a dominance score) and categorize cows into 5 dominance categories based on these ratings. To ensure a consistent Elo-Rating distribution between group sizes, 2 cows from each dominance category were randomly assigned to each group of 10. Data from the last 3 days in each treatment were used for analysis of agonistic interaction frequency. Although the groups of 10 were more variable, the average number of agonistic interactions per cow in groups of 50 (34.1±2.4, mean±SE; 26.5–41.7, 95% CI) was similar to that in groups of 10 (31.1±5.0, mean±SE; 15.0–47.2, 95% CI). 81.5±5.2% (mean±SD) of dyads had the same directionality across group sizes. My findings indicate that dominance and agonistic behaviour are multidimensional and that group size may not be a major driver of the frequency of physical agonistic interactions at the feeder in dairy cattle.
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