Long-term effects of food allowance and housing on development of stereotypies in pigs

Abstract

In a previous study (Terlouw et al., 1991, Anim. Behav., 42: 981–991) on the effects of physical restraint and food allowance on the development of stereotypies in pigs ( Sus scrofa), it was found that in both restrained and loose-housed pigs low food levels were accompanied by increased levels of total activity, and of chain manipulation and drinking. We have suggested that these activities may have been the expression of high levels of motivation to feed or forage, which in both housing systems were directed to the chain and to the drinker. The present results confirm the effects of food restriction on the development of stereotypies, as also in the second and third parity individuals receiving a low food allowance (2.5 kg of food per day) spent more time being active, performing higher levels of most activities, in particular chain manipulation and drinking, than individuals receiving a high food allowance (4.0 kg day −1). The effects of physical restraint were mostly limited to the low-fed group: low-fed restrained sows were slightly more active, and they performed more drinking and inactive standing than low-fed loose-housed sows. These effects were restricted to certain times of day. The present study was also the first to investigate the behaviour of the same sows over several parities, and it found that overall levels of total activity and of chain manipulation did not increase over parities. Low-fed sows showed, however, a small increase in sham oral activity and drinking-related activity. High-fed sows showed an increase in feeding rate over parities and low levels of chain manipulation. Positive correlations between individual levels across parities indicated that, in contrast to previous suggestions, sows were relatively consistent in their behaviour. In the fourth parity, increasing the food allowance to 4.0 kg day −1 did not reduce stereotypies in previously low-fed sows; reducing food allowance in previously high-fed sows was accompanied by an increase in activity in the longer term. Stereotypies occurred mainly after the meal with post-feeding activities occurring in a specific sequence. High-fed sows performed a short period of nosing and rooting the trough, then drank and lay down. Low-fed sows, in contrast, persisted in their drinking and in addition performed chain manipulation. The behavioural processes that may underlie these effects are discussed.