Influence of energy supply on growth characteristics in pigs and consequences for growth modelling

The aim of the present paper is to investigate the effect of energy supplies on growth characteristics in pigs when protein supplies are non-limiting. An experimental program was carried out at INRA between 1992 and 1994 and involved 60 pigs from three types fed at five energy levels. The effects of energy intake on protein deposition (PD) and lean gain on one hand and on lipid deposition (LD) and fat gain on the other hand were found to be very similar, which is logical with the fact that more than 55% of PD and 80% of LD are deposited in lean and fat tissues, respectively. Our results indicate that PD increases with energy supplies according to a linear-plateau relationship, which slope (beta(p)) and maximum value are influenced by genotype, sex, and stage of growth. From our results and those of literature, beta(p) is reported to vary between 2.9 and 6.1 g per MJ digestible energy (DE) intake over the 45-100 kg body weight (BW) range. Simultaneously, LD increases linearly with energy level but neither the genotype nor the sex influence significantly the slope of the relationship (14.5 g/MJ DE between 45-100 kg BW). Differences in growth response to energy intake between types of pigs result in an important variation in BW gain and its composition associated to energy intake. Therefore, characterisation of relationships between growth components and energy intake specific to each type of pig is necessary for modelling response to energy intake.