Factors affecting foraging motivation in the domestic pig

Abstract

The welfare of farm animals is currently a topic of both scientific investigation and public concern. The aim of this thesis was to investigate motivational factors affecting the expression of foraging behaviour in domestic pigs. This topic was chosen because a number of recent scientific investigations have implicated commercial feeding regimes as being causal in reducing pig welfare.

Most of the experiments reported in this thesis used operant methodology in which pigs had to learn to perform a behavioural response to receive food reinforcement. The main aspects investigated were: the effects of social constraints on feeding behaviour; the effect of information associated with reinforcer delivery on contrafreeloading (where the same food is simultaneously offered free and contingent on an operant response); the effect of operant design on food intake and on operant choice; the effect of food level and a foraging device (The Edinburgh Foodball’) on pigs’ time budget; and the effect of reinforcement rate from the Foodball on the time budget.

The results showed that: pigs are highly adaptable and flexible foragers able to overcome social constraints associated with feeding by altering the expression and temporal patterning of feeding variables (e.g., feeding rate); that information associated with reinforcer delivery had little effect on contrafreeloading and that pigs at least under these experimental conditions preferred free food over operant contingent food; that the design of an operant device can significantly influence the level of operant responding and the level of food intake; that given the opportunity food motivated pigs express their feeding motivation as complex and variable foraging behaviour; and that pigs respond to a decrease in the rate of food reinforcement by increasing both the proportion of time they forage for, and the frequency of their foraging responses.

This thesis has shown the effects of a number of factors on the expression of foraging and feeding behaviour in domestic pigs. Although it remains unclear whether or not being able to forage affects the welfare of pigs, the species-specific operant methodology developed in this thesis I believe will allow the welfare requirements of pigs to be more accurately assessed.