Laterality as a tool for assessing welfare risk in the domestic pig (Sus scrofa)

Abstract

The domestic pig (Sus scrofa) is among the most intensively farmed species in the world and faces significant welfare challenges. Tools capable of assessing pigs’ welfare risk are sorely lacking. Studies on other species suggest that lateral bias, an indicator of cerebral hemispheric dominance, may harbour potential as a non-invasive method of assessing welfare risk. Yet, the lateral preferences of pigs have received little scientific attention. This thesis therefore aimed to explore lateral bias in the domestic pig and examine its association with physical and psychological indicators of welfare. Study 1 explored five laterality measures (snout use, step-up, detour, tail curling, lying side) in 50 farmed pigs to determine their usefulness in a farm setting. Lying side and snout use yielded largely ambilateral responses, while tail curling was not considered a reliable measure.

 Individual-level side preferences were observed for the step-up and detour tasks, which also showed good test-retest reliability, and were therefore employed in the subsequent studies. Study 2 examined associations between pigs’ (n = 50) laterality and physical and psychological welfare indicators. Right-sided pigs were bolder and more explorative than left-sided pigs, while left-sided pigs had a significantly higher average daily gain. Study 3 investigated the relationship between laterality and emotional wellbeing in 42 pigs using the judgement bias task. No significant differences were found between laterality groups in their responses to ambiguous cues, although increasing left-sidedness was associated with a faster approach to one of the ambiguous cues. Study 4 examined whether laterality could predict pigs’ (n = 42) affective responses to regrouping, and whether ‘at-risk’ pigs could be targeted with an enrichment intervention. Left-sided pigs showed a significant pessimistic shift following regrouping. Descriptive analysis indicated enrichment buffered ambilateral and left-sided animals. Overall, the findings suggest that pigs’ lateralised behaviour may be related to some welfare outcomes.

Thesis is embargoed until 31 July 2029.

Date of Award	Jul 2026
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Co-operative Awards in Science and Technology (CAST) studentship (Department for the Economy)
Supervisor	Deborah Wells (Supervisor), Gareth Arnott (Supervisor) & Grace Carroll (Supervisor)