The environmental consequences of feeding growing-finishing pigs with reduced dietary nutrient levels

Life cycle assessment (LCA) has been used in many studies to evaluate the effect offeeding strategy on the environmental impact of pig production. However, in Brazil thereare hardly any results on this topic. The objective of this study was to evaluate the effect ofdiet formulation with nutritional requirements estimated by mathematical model on LCAimpact of pigs from 25 to 130 kg live weight, produced in a typical farm in the South ofBrazil. Forty gilts and 40 barrows (24.5 ± 1.8 kg) were distributed in a randomized blockdesign with two treatments, 10 replications per treatment, and four animals perexperimental unit. The feeding program was in four phases. Two diets were formulated foreach feeding phase: LN - adjusted using InraPorc® model to minimize the crude protein,amino acids and phosphorus excess (LN); ST - adjusted to suit the standard Brazilianrecommendations (Rostagno et al., 2011). The LCA considered the process of pig fatteningincluding production and transport of feed ingredients and complete feeds, raising the pigs,and manure management. Impacts were calculated at farm gate and the functional unit wasone kilogram of body weight gain over fattening. The LCA calculations were performed foreach experimental unit according to its own performance and excretion. Data weresubjected to ANOVA with the main effects of treatment, block, sex and interaction betweentreatment and sex, using SAS. In the overall period, pigs fed with LN diet consumed 16.1and 10.1% less crude protein and total phosphorus, respectively. The LN diets showed to bean efficient feeding strategy to reduce the impact of pig production on the variablesappointed as indicators of climate change by about 3.75%. Similar effects were observedfor acidification and eutrophication, which were reduced 8.19 and 9.47%, respectively.Terrestrial ecotoxicity and land occupation were 4.02 and 8.79% lower, respectively, whenpigs were fed with LN diets. Conversely, cumulative energy demand was not affected bydietary nutrient reduction. It was concluded that the reduction of crude protein, amino acidsand phosphorus contents to better adjust nutrient supplies to animals requirements appearsvery effective for reducing life cycle impact of pig fattening.