Further quantification of pigs needs for food using operant conditioning

Extract

The study of motivational states underlying behaviour is seen as critical to understanding the implications of restricted husbandry conditions on animal welfare. Yet the measurement of the strength of motivation remains a perennial problem in welfare studies. Previous work at Edinburgh using operant conditioning identified an apparently high level of feeding motivation throughout the day in pigs fed [ARC, 1981] recommended levels for sows and boars [Lawrence et al. 1988]. Pigs trained to press a panel consistently 10 times for a food reward (fixed ratio or FR responding) maintained high levels of panel pressing across the day when offered 0.6 of their ad libitum intake approximating to ARC (1981) recommended feeding levels. However, as the level of operant responding required was not great, it is arguable to what extend these results demonstrate a strong need for food by pigs on restricted feeding. The present paper reports on an experiment to test more accutely the strength of feeding motivation in relation to food restriction by comparing responding on FR with that on a progressive ratio (PR) where the animal has to work progressively harder for successive rewards. It was hoped that PR. reputedly a sensitive measure of motivation, would indicate with greater certainty restrict fed pigs need for food.