BEHAVIOR AND SHELTER USE BY OUTDOOR SOWS

Although the behaviour of domestic pigs kept in seminatural environmen ts has been studied extensively, the behaviour of pigs on commercial o utdoor units has been largely neglected. The behaviour of groups of pr egnant and lactating outdoor sows was studied biweekly during daylight hours over a 12-month period. The behaviour of sows was classified in to nine mutually exclusive behaviour categories: standing, walking, fo raging, sitting, lying on side, lying sternally, feeding, drinking and wallowing. The proportion of observations in each these: categories w as most strongly related to the stage of reproductive cycle, with seas on and climate having relatively small effects. Activity, defined as s tanding, walking, foraging, feeding or drinking, showed a bimodal patt ern during daylight hours. Newly farrowed sows spent on average 15.3% (range 9.34-31.4%) of observations outside their hut, whereas prepartu rient sows spent 49.2% (range 29.8-89.8%) observations outside, and ex hibited behaviours indicative of heat stress in all seasons. Pregnant sows spent most observations foraging, 25.9% (range 12.0-52.2%). A log istic regression model for predicting the proportion of daylight hours spent outside the hut accounted for only 45% of the variation of shel ter use. When factors were fitted singly, the stage of reproductive cy cle explained 30% of variation; no single climatic factor accounted fo r more than 5%. The minimisation of heat loss did not appear to be a m ajor goal of these sows. (C) 1998 Elsevier Science B.V.