Above 65 kg empty BW, protein deposition is greater in pigs fed protein-restricted compared to standard diets. It is unclear whether the greater CP deposition rate in the finisher period results from the restricted CP supply in the grower phase. To elucidate this question, a growth performance study (22.1-110.0 kg BW) was conducted with 48 Swiss Large White pigs. They were assigned within litter to 3 dietary treatments: C, LP-F and LP-GF. The grower-finisher diets of treatment C were formulated based on the Swiss feeding recommendations whereas those in the LP-GF treatment contained 20% lower digestible CP and essential amino acids levels than diets C. Pigs of the LP-GF group were offered in the grower and finisher period the standard and the low CP diets, respectively. The pigs were reared in 1 large pen, equipped with 6 automatic feeders, which allowed measuring the individual ad-libitum feed intake per visit. The BW was determined weekly and carcass composition at slaughter was determined by Dual-X-ray-Absorptiometry (DXA). Growth performance and DXA data were analysed with a linear mixed model using treatment as fixed and litter, litter size and farrowing series as random effects. Despite total CP intake was 6 and 16% lower (P<0.05) in the LP-GF than the LP-F and C groups, respectively, overall ADG among treatments did not differ. Accordingly, gain-to-CP-intake ratio was 9 and 20% greater (P<0.05) in the LP-GF than the LP-F and C group. However, relative amount of lean and fat tissue was 1.9%-units lower respectively greater (P<0.05) in the LP-GF than the LP-F and C groups. Therefore, lowering the CP supply by 20% in the grower and finisher compared to solely the finisher period or not at all has no detrimental effect on growth performance, markedly improves CP utilization for growth but slightly affects negatively the carcass composition.
