Influence of dietary net energy content on performance of growing pigs fed low crude protein diets supplemented with crystalline amino acids

Objective: To investigate the effects of dietary net energy (NE) content on the performance of growing pigs fed low-protein diets supplemented with crystalline amino acids. Materials and methods: A total of 144 barrows (22.96 +/- 2.72 kg, Experiment One) or 360 barrows (27.80 +/- 3.48 kg, Experiment Two) were assigned to six treatments. Diets in both experiments were based on corn and soybean meal, including an unsupplemented high-crude-protein (CP) diet (19.0% CP, 2.50 Mcal NE per kg) and five low-CP diets (4% lower CP) supplemented with lysine, methionine, threonine, and tryptophan. For Experiment One, five levels of NE (2.64, 2.58, 2.50, 2.42, and 2.36 Mcal per kg) were formulated in the low-protein diets. In Experiment Two, the low-protein diets contained 2.45, 2.40, 2.35, 2.30, and 2.25 Mcal NE per kg. Results: In Experiment One, for pigs on low-CP diets with different NE levels, ADG (P<.05) and gain:NE intake (kg per Meal NE) increased linearly with decreasing NE levels (P<.01). In Experiment Two, for pigs on low-CP diets with different NE levels, there was a significant quadratic increase in ADG, gain:feed, and gain:NE intake as net energy levels increased from 2.25 to 2.35 Meal NE per kg (P<.05). Implications: Feeding a low-CP, amino-acid-supplemented, corn-soybean-meal-based diet with a proper NE level maximizes the performance of growing pigs. Optimum performance will be obtained if the diet provides approximately 2.40 Mcal NE per kg.