PSIX-21 Effect of reduced digestible protein and amino acid supply imposed in the grower and finisher period or solely in the finisher period on growth performance and feeding behaviour

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, a growth performance study (22.1–110.0 kg BW) was performed with 48 Large-White pigs. They were assigned within litter to 3 dietary treatments: C, LP-F, LP-GF. The grower-finisher diets of treatment C were formulated based on the Swiss feeding recommendations whereas those for the LP-GF treatment contained 20% lower digestible CP and essential amino acids levels than the C diets. 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 one large pen, equipped with 6 automatic feeders, which allowed measuring the individual ad-libitum feed intake per visit. The BW was determined weekly. Growth performance and feed behaviour 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 from 22.1 to 110.0 kg BW 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. In the grower, but not the finisher period, LP-GF pigs visited 1.6-times more (P < 0.05) the feeder and ingested 12% less (P < 0.05) feed per visit than C and LP-F pigs. These data suggest that 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 and markedly improves CP utilization for growth.