Effects of Dietary Electrolyte Balance and Crude Protein on Growth Performance and Carcass Characteristics of Finishing Pigs from 110 to 130 Kg

Economic and environmental factors have compelled nutritionists to develop low-protein, AA fortified diets that deliver performance equivalent to traditional formulations. In some instances, low-protein AA fortified diets have led to poorer performance in finishing pigs than conventional diets. Along with low CP concentrations, with crystalline AA, there is proportional decrease in dietary electrolyte balance (dEB). To evaluate the effects of dEB and determine the optimum dietary CP level in finishing pigs, two experiments were conducted. In Exp. 1, 288 pigs (PIC 327×1050, initially 110.4 kg) were used in a 20-d trial. Pens of 8 pigs were randomly assigned to 4 dietary treatments with 8 replications per treatment. Treatments were arranged in a 2×2 factorial with main effects of CP (10 or 13%) and dEB (48 or 107 mEq/kg). Pigs fed 13% CP diets had greater (P=0.001) ADG (0.79 vs 0.71 kg), (P=0.037) final BW and (P<0.001) G:F (0.279 vs 0.253) compared with pigs fed the 10% CP diets. Marginal significance for a CP×dEB interaction (P=0.083) was observed for ADFI because intake numerically decreased when dEB was increased for pigs fed 10% CP whereas intake increased as dEB was increased for pigs fed 13% CP diets. For carcass performance, pigs fed the diets with 13% CP had increased (P=0.001) HCW and HCW ADG and improved (P=0.001) HCW G:F compared with pigs fed 10% CP diets. In Exp. 2, 224 pigs (PIC 327×1050, initially 109.4 kg) were used in a 20-d trial. Pens of 7 pigs were assigned to 4 levels of dietary CP (10, 11, 12, and 13%) with 8 replications per treatment. For overall growth performance (d 0 to 20), increasing CP increased (linear, P<0.05 and quadratic, P<0.10) ADG (0.77, 0.86, 0.91, and 0.90 kg), ADFI (2.58, 2.72, 2.84, and 2.76 kg) and HCW ADG with the greatest response for pigs fed the diet with 12% CP. Increasing diet CP also improved (linear, P<0.05) G:F (0.299, 0.314, 0.322, and 0.327), NE caloric efficiency, final BW, HCW and HCW G:F. In summary, dEB in the tested range had no effects on growth performance nor carcass performance. Optimum dietary CP was reached by pigs fed diets with 12% CP. Rationale for poor feed efficiency and low feed intake when pigs are fed diets with less than 12% CP remains unclear.