0
In recent years, environmental protection efforts have increasingly targeted the reduction of harmful industrial gas emissions as well as biogenic compound excretion and ammonia emissions from agriculture, including animal production.
Objective: The aim of this study was to determine the effects of reduced–crude protein diets with limiting essential amino acids and different feeding systems (two- vs. three-phase) on crude protein digestibility, nitrogen retention and utilization, fecal and urinary pH, nitrogen and ammonia concentrations, and nitrogen excretion in pigs.
Methods: Digestibility-balance trials were performed on 24 growing-finishing pigs housed in individual metabolism crates, assigned to three diets and fed in two- or three-phase systems. The pigs were fed the following diets: C-control diet; L-low-protein diet where the levels of crude protein and essential amino acids (lysine, methionine + cystine, threonine, and tryptophan) were reduced by 15% relative to diet C; L+AA-low-protein diet supplemented with crystalline lysine, methionine, threonine, and tryptophan to the standard levels (as in diet C).
Results: Diets L fed to pigs in two- and three-phase feeding systems significantly decreased crude protein digestibility and nitrogen retention, particularly in the three-phase system. The supplementation of L+AA diets with crystalline essential amino acids improved crude protein digestibility and nitrogen retention and utilization, particularly in the two-phase system. Reduced crude protein and essential amino acid levels in diet L significantly increased fecal and urinary acidity in both feeding systems. Supplementation with essential amino acids increased urinary pH and slightly increased fecal pH but had no effect on fecal ammonia concentration. Fecal pH and total nitrogen were slightly higher in the two-phase system than in the three-phase system, while fecal ammonia was similar in both systems. The three-phase system reduced urinary pH and total urinary nitrogen but had no significant effect on urinary ammonia.
Conclusion: Reducing crude protein by 20–25 g/kg and essential amino acids in pig diets decreased nitrogen excretion by 18.7% and 15.6% in the two- and three-phase systems, respectively. Supplementing low-protein diets with lysine, methionine, threonine, and tryptophan further reduced nitrogen excretion.
Sobotka W, Drażbo A. The Effect of Dietary Protein Restriction in Phase Feeding Systems on Nitrogen Metabolism and Excretion in Pig Production. Animals. 2025; 15(11): 1521. https://doi.org/10.3390/ani15111521