Co-occurrence of sudden feeding behaviour deviations and welfare issue onsets in growing-finishing pigs.

Background: Modern sensor technologies and algorithms have the potential to continuously monitor indicators of individual animal welfare, but in growing-finishing pigs the validity of such welfare monitoring remains low for unclear reasons. This study explored how sudden deviations in individual pig feeding behaviour, detected as alerts by a dynamic linear model with Kalman filter, relate to the onset of welfare issues.

Results: Alerts frequencies varied across feeding behaviour components, with higher occurrences for feed intake, feeding duration, feeding rate and night intake (approximately 14.5% of days with an alert) than for feeding frequency and circadian rhythm strength (approximately 7.7% of days with an alert). Limited temporal overlap was observed between feeding components (mean co-occurrence: 18 ± 2%, range 8-47%). Alert prevalence was lower in the first month of the growing-finishing phase for all feeding components except frequency and night intake, which showed opposing patterns. Substantial inter-individual variation in alert prevalence was observed (range: 1.1 - 22.2% alert days). The co-occurrence of alerts and welfare issue onsets, i.e. the sensitivity, was poor and not better than expected by chance (health issues: 2.0 - 48.7%, heat stress: 6.4 - 23.2%). Highest sensitivities were obtained for combinations of coughing, ear tip damage, lameness, rectal prolapse, or tail damage with feed intake, feeding duration or night intake. Sensitivities dropped further when only positive (range: 0.0 - 30.8%) or negative (range: 1.0 - 33.3%) alerts were considered. Sensitivities beyond chance expectations were obtained for feed intake, feeding duration and/or night intake in lame or tail-bitten pigs with specific feeding strategies (range: 4.6 - 66.7%).

Conclusions: These results suggest that sudden deviations in feeding behaviour co-occur poorly with onsets of health issues and heat stress, and that current achievements may be largely based on statistical probabilities. However, mild sensitivities were identified for certain health issues and feeding components, especially for pigs with specific feeding strategies. In addition, the results imply that different types of deviations exist, which differ in suddenness and persistence across the welfare issues' duration. Considering the importance of individual feeding strategies and basal feeding behaviour, stimulating more consistent basal behaviour by improving pigs' housing conditions may reveal new avenues for continuous welfare monitoring.