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In pig production, dietary crude protein (CP) is traditionally high due to the use of soybean meal as a primary protein source, which often leads to excess amino acids and increased nitrogen excretion, contributing to environmental pollution. High CP diets can also harm gut health through protein fermentation and are becoming costlier due to climate change and rising demand for soybean meal. Low-protein diets supplemented with crystalline amino acids offer a solution by precisely meeting amino acid requirements while reducing CP levels. However, the impact of low-protein diets on pig growth performance remains inconsistent and may vary by growth stage. This study aimed to evaluate how reducing CP with all indispensable amino acid supplementation affects the growth performance of nursery, growing, and finishing pigs.
Methods: There were a total of 90 pigs (45 barrows and 45 gilts) at the growing stage, and 72 pigs (36 barrows and 36 gilts) at the finishing stage. Pigs with average weights of 30.6 kg and 58.3 kg were assigned to three dietary treatments with six replicates. The dietary treatments consisted of three diets, each replacing soybean meal with corn and crystalline amino acids, leading to a 2% reduction in CP levels from the upper limits established for each growth stage. The upper CP limits were set at 16% for both stages, that leaves the three treatments: 16% CP, 14% CP, and 12% CP.
Results: Reducing the concentration of dietary CP had no effect on the growth performance of growing pigs, regardless of phase. However, in the finishing stage, CP reduction decreased the average daily feed intake between weeks 3 to 6 and over the entire 0-6 week period. No effects were observed on body weight, average daily gain, or gain-to-feed ratio.
Conclusion: Reduction of the dietary crude protein, particularly down to 12%, appears to be a feasible option during the growing and finishing stages, without adverse effects on growth performance.
Cho I, Kong C. Growth performance of pigs fed low-protein diets supplemented with crystalline amino acids at different growth stages. Anim Biosci. 2025 Feb; 38(2): 316-324. https://doi.org/10.5713/ab.24.0339
