An investigation of dietary and individual factors linked to harmful social behaviour in pigs

Abstract

The primary aim of research within this thesis was to investigate the effect of dietary factors such as protein level, abrupt changes in diet, and inclusion of antibiotics on the performance of harmful social behaviours in fattening pigs.

An initial study investigated finishing pigs fed either a control diet (15.5% crude protein, CP) or a low crude protein diet (13.5% CP). Pigs on the low-protein diet exhibited more limb-directed behaviour, while tail-biting was more frequent in males, but not females.

A further study was conducted to understand the effects of dietary protein level and abrupt dietary change in weaned pigs. Pigs were assigned to three diets: Control (CON) (Starter 1: 20.8% CP, starter 2 18.6% CP), Moderately Low Protein (MLP) (Starter 1: 18.4% CP, starter 2: 17.9% CP) and a Low Protein treatment (LP) (starter 1: 16.3% CP, starter 2: 16% CP). Harmful behaviours were not significantly affected by protein levels, but pigs on the MLP diet had longer feeding bouts.

A dietary change at 13 days post-weaning led to increased exploration and harmful social behaviours, though a second change at 28 days had no marked effect. This thesis also explored the effects of removing antibiotics from the diet of weaned pigs. While growth and harmful social behaviours were unaffected, pigs fed antibiotic-free diets had poorer gut health and were more likely to engage in fighting, indicating reduced welfare.

Additionally, the prevalence of gastric ulcers and dental issues in pigs was investigated. The prevalence of gastric ulceration in the assessed pigs was high, suggesting this could be an important risk factor. It was also apparent that slaughter-age pigs can have dental health problems including broken and blackened teeth. Tooth eruption was also evident throughout the weaner, grower and finisher stages, and timings of tooth eruption mostly aligned with previous literature.

Date of Award	Dec 2024
Original language	English
Awarding Institution	Queen's University Belfast
Sponsors	Department of Agriculture, Environment and Rural Affairs
Supervisor	Niamh O'Connell (Supervisor), Grace Carroll (Supervisor) & Stephanie Buijs (Supervisor)