Behaviour and shelter use by outdoor sows

Abstract

Although the behaviour of domestic pigs kept in seminatural environments has been studied extensively, the behaviour of pigs on commercial outdoor units has been largely neglected. The behaviour of groups of pregnant and lactating outdoor sows was studied biweekly during daylight hours over a 12-month period. The behaviour of sows was classified into nine mutually exclusive behaviour categories: standing, walking, foraging, sitting, lying on side, lying sternally, feeding, drinking and wallowing. The proportion of observations in each these categories was most strongly related to the stage of reproductive cycle, with season and climate having relatively small effects. Activity, defined as standing, walking, foraging, feeding or drinking, showed a bimodal pattern during daylight hours. Newly farrowed sows spent on average 15.3% (range 9.34–31.4%) of observations outside their hut, whereas preparturient sows spent 49.2% (range 29.8–89.8%) observations outside, and exhibited behaviours indicative of heat stress in all seasons. Pregnant sows spent most observations foraging, 25.9% (range 12.0–52.2%). A logistic regression model for predicting the proportion of daylight hours spent outside the hut accounted for only 45% of the variation of shelter use. When factors were fitted singly, the stage of reproductive cycle explained 30% of variation; no single climatic factor accounted for more than 5%. The minimisation of heat loss did not appear to be a major goal of these sows.