Relationship between the siring capacity of beef bulls and their behaviour in multi-sire breeding groups measured by remote monitoring technologies

The objective was to investigate the relationship between siring capacity and behavioural metrics of beef bulls in multi-sire groups during the breeding season, using remote monitoring technologies (RMT). Behavioural metrics from 12 bulls in 2023 and 13 bulls in 2024 were estimated using accelerometers, GPS, and proximity sensors. The association between behavioural metrics and siring capacity per week (SR/week, computed from DNA parentage results) was analysed using generalized mixed-effect models while accounting for candidate covariates. Several behaviours were associated with SR/week when accounted for age (P≤0.01), percentage of cows available for breeding (% cows/week, P≤0.001), and lameness status (P≤0.05), with significant interactions between behaviours and covariates. Time spent walking, distance travelled, and velocity were positively associated with SR/week (P<0.001) and moderated by % cows/week (P<0.001), with stronger positive effects as % cows/week reduced. Time spent grazing and the size of home ranges were negatively associated with SR/week (P<0.001) and moderated by % cows/week (P<0.001), with stronger negative effects as % cows/week reduced. In a subset of bulls, social selectivity and time in proximity to other bulls were positively associated with SR/week while moderated by % cows/week and lameness status, respectively (P≤0.04). Time spent in proximity to cows was positively associated with SR/week and moderated by % cows/week (P=0.002). In conclusion, several behavioural metrics associated with beef bulls’ siring capacity were identified using RMT, unveiling behavioural aspects explaining differences in reproductive success. This study addresses gaps in knowledge about bull behaviour in multi-sire breeding groups associated with their siring capacity and provides insights for remote breeding monitoring systems.