Testing several genotypes on one diet may impose nutritional constraints on growth for particular genotypes. In the study, three genotypes were tested on four isoenergetic dietary regimes to determine if a genotype with diet interaction existed for the pattern of cumulative protein intake and total protein intake.

There were 150 Large White pigs from the lean, control and fat lines, with divergent selection for lean growth rate over seven generations. In each line, there were 10 full-sib groups and within each full-sib group, one pig was allocated to each of the high (H : 220 g crude protein (CP)/kg) or low (L : 120 g CP/kg) protein diets, a standard test diet (S : 195 g CP/kg) and the two remaining pigs were tested using the diet-choice procedure (DC), using the H and L diets. Pigs were performance tested from 30 to 85 kg, with individual penning.