Influence of increasing temperature and live weight on the feeding behaviour of group-housed growing pigs

The individual feeding behaviour of group-housed Piétrain x Large White barrows was studied in groups of 3 to 4 pigs over two stages of growth (S1 and S2), corresponding to respective average live weights of 49 and 75 kg. For each stage of growth, room temperature varied in a cyclic way from 19 to 29°C and 29 to 19°C with 3 or 4 consecutive days at each of the following temperatures: 19, 22, 25, 27 or 29°C. Daily number of meals was not affected by temperature (10.4 on average), but both meal size and meal duration decreased between 19 and 29°C: from 265 to 195 g and from 9 to 6 minutes, respectively. This corresponded to an average decrease of 65 g/°C of daily feed intake between 19 and 29°C. An equation is proposed to predict the voluntary food intake from temperature and body weight as covariates. According to this equation, the effects of temperature and body weight were not linear and a significant interaction was found between temperature and body weight. Indeed, the reduction in food intake was more pronounced at the highest temperatures and in heaviest pigs. At S1, the daily feed intake decreased by 28 g/°C/d between 19 and 25°C and by 80 g/°C/d between 25 and 29°C. At S2, the corresponding values were 70 and 122 g/°C/d, respectively.