This paper examined a genotype with feeding regime interaction by performance testing pigs, selected for lean growth on ad-libitum or restricted feeding, on both the normal and the alternative feeding regime.

Large White (LW) and Landrace (LR) pigs from divergent selection lines were for four generations for lean growth either on an ad-libitum (LGA) or a restricted (LGS) feeding regime. In each selection group, there were high, low and control lines, which consisted of 10 sires and 20 dams. On average, 3 boars and 3 gilts were tested per litter, with one boar and one gilt per litter tested on the alternative feeding regime. On ad-libitum feeding, there were 181 LGA and 94 LGS LW pigs and 162 LGA and 67 LGS LR pigs. On restricted feeding, 92 LGA and 212 LGS LW and 53 LGA and 135 LGS LR pigs were tested.

Performance test. The performance test was over a fixed weight range of 30±3 kg to 85±5 kg for ad-libitum fed pigs and for a fixed time of 84 days for restricted fed pigs. Restricted feeding was equal to 0.75 g/g of daily food intake of ad-libitum fed pigs. All pigs were individually penned and fed a high energy (13.8 MJ DE/kg DM) and high protein (210 g/kg DM crude protein) pelleted ration.