Use of different cooling systems by pregnant sows in experimental pen

Literature suggests that pregnant sows are able to select the types of cooling they prefer in the pen. This hypothesis was tested by comparing different cooling regimes. A fixed group of four pregnant sows was selected; six cycles of observations were carried out during summer. Inside the pen, four areas were selected and treated with different regimes; not cooled, cooled with an airstream, cooled with an airstream and water on the floor, and cooled with water on the floor. The use of the different areas by the sows was monitored in relation to air temperature and the temperature–humidity index [Ingram D L (1965). Evaporative cooling in the pig. Nature, 207, 415–416.]. The presence of the sows in the cooled areas became more important with increasing temperature. Below a temperature of 22 °C, areas that were not cooled, or were cooled solely by an airstream, were favoured. The occupancy of the area that was solely cooled by an airstream tended to increase up to a temperature of 30 °C, when the area cooled by water and an airstream was favoured. The use of the solely water-cooled area increased with temperature, especially with high temperatures. It was concluded that the behaviour of the sows, in terms of which area of the pen they occupied, was a function of air temperature. During the day, there appeared to be threshold temperatures above which sows moved to areas that they found more comfortable.