Determination of the Optimum Levels of Dietary Crude Protein for Growth Performance and Carcass Characteristics of Finishing Pigs from 240 to 280 lb

A total of 224 pigs (PIC 327 × 1050, initially 241.1 lb) were used in a 20-d trial to determine the optimum dietary CP concentration for growth performance and carcass characteristics of finishing pigs. Pens of 7 pigs were allotted by BW and randomly assigned to 1 of 4 dietary treatments with 7 or 8 replications per treatment. Dietary treatments included 4 levels of CP (10, 11, 12, and 13%) that were formed by reducing the amount of crystalline Lys in a corn-soybean meal diet. At d 20, pigs were transported to a packing plant for processing and carcass data collection. For overall growth performance (d 0 to 20), increasing CP increased (linear, P < 0.05 and quadratic, P < 0.10) ADG, ADFI, and HCW ADG with the greatest response for pigs fed the diet with 12% CP. Increasing diet CP also improved (linear, P < 0.05) F/G, NE caloric efficiency, final BW, HCW, and HCW F/G. In conclusion, poorer performance of pigs fed diets under 12% CP was predominantly explained by feed intake but the mechanisms underlying regulation of feed consumption when feeding lower CP remains unclear.