Relationship between residual energy intake and the behaviour of growing pigs from three genetic lines

Residual metabolizable energy intake (RMEI) is the difference between metabolizable energy intake (MEI) and predicted production and maintenance requirements. In growing pigs from three genetic lines, namely Genex Meishan-derived dam line (GM), Synthetic Genex 3000 (SG) and purebred Large White (LW), RMEI was determined and related to behaviour by factorial Partial Least Squares analysis. Behaviour was measured by observations of daily behaviour in the pen, postures, feeding behaviour, aggressive behaviour after mixing and ease of handling at weighing. The RMEI obtained for the GM pigs was lower (P = 0.003) than that of the two other lines studied (LW and SG). This difference may result from inaccuracy in the estimation of requirements. A small proportion of these differences were explained by differences in behaviour. Indeed, standing posture, time spent in the feeder, toy manipulation, aggressive and locomotor behaviour explained part of the variation in RMEI, presumably because an increase in these physical activities induces higher energy expenditure. Vocalisations during manipulations at weighing were the only behaviour related to stress that influenced RMEI.