Reducing crude protein and supplementing amino acids in growing pig (50-70 kg) diets reduce nitrogen excretion but promotes different environmental impacts when using life cycle assessment

Abstract

The objective of this study was to evaluate the performance, digestibility, and environmental impact of pigs in the growth phase receiving diets with reduced crude protein and supplementation of amino acids. In the metabolism experiment, 20 crossbred barrows with an initial average weight of 63.62 ± 2.21 kg were housed in metabolic cages, with four treatments and five replications, one animal per experimental unit. In performance experiment, 40 crossbred barrows were used, with an initial average weight of 49.92 ± 0.92 kg, with four treatments, ten replications. The treatments used in both experiments consisted of four diets containing 16, 15, 14, and 13% of CP, and supplementation with amino acids to meet the requirements of all digestible amino acids. For performance, backfat thickness, and depth of the longissimus lumborum muscle, no differences were observed. Plasma urea was lower in animals fed diets with protein reduction as well as the excretion of N urine and total N, but no differences were observed for retained N, P absorbed, P ingested, and P feces. Through the life cycle assessment, for the categories of eutrophication potential and land occupation, the protein reduction mitigated the impacts when referring to soybean meal produced in the southern region, but the protein reduction provided an increase in impact when the category evaluated was cumulative energy demand, considering the soybean produced in the south and that produced in the central west region.