Residual food consumption in growing pigs fed ad libitum : method of calculation and genetic variability

Residual food consumption (RFC) in growing pigs represents the deviation of the actual daily food consumption of an animal from its consumption as predicted on the basis of its growth and maintenance requirements. Variation in RFC therefore reflects differences in the efficiency with which animals digest and utilize energy when adjusted for similar performances.RFC is higher of about 70 g/day in winter batches, probably in relation with the energetic cost of body temperature regulation. French Landrace pigs show higher residual food intake than Large White, by about 60 g/day i.e. 0.4 standard deviation unit of the trait. Such a gap might originate from breed differences in basal metabolism or physical activity. Despite the myriad of causes contributing to the variability in RFC, a noticeable amount of this variability (25 %) is heritable, which makes possible an efficient selection for this criterion. RFC shows strong positive correlations with food conversion ratio (about 0.6) and daily food intake (genetic correlation = 0.84 on average). In contrast, phenotypic correlations are close to zero with average daily gain and backfat thickness. Estimated genetic correlations of RFC with feeding behaviour criteria suggest that selection in favour of « nibblers » (many meals of small size) would lead, at least in the Landrace breed, to a decrease of residual food consumption.