The environmental consequences of feeding growing-finishing pigs with reduced dietary nutrient levels
Résumé
Life cycle assessment (LCA) has been used in many studies to evaluate the effect of
feeding strategy on the environmental impact of pig production. However, in Brazil there
are hardly any results on this topic. The objective of this study was to evaluate the effect of
diet formulation with nutritional requirements estimated by mathematical model on LCA
impact of pigs from 25 to 130 kg live weight, produced in a typical farm in the South of
Brazil. Forty gilts and 40 barrows (24.5 ± 1.8 kg) were distributed in a randomized block
design with two treatments, 10 replications per treatment, and four animals per
experimental unit. The feeding program was in four phases. Two diets were formulated for
each feeding phase: LN - adjusted using InraPorc® model to minimize the crude protein,
amino acids and phosphorus excess (LN); ST - adjusted to suit the standard Brazilian
recommendations (Rostagno et al., 2011). The LCA considered the process of pig fattening
including 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 was
one kilogram of body weight gain over fattening. The LCA calculations were performed for
each experimental unit according to its own performance and excretion. Data were
subjected to ANOVA with the main effects of treatment, block, sex and interaction between
treatment and sex, using SAS. In the overall period, pigs fed with LN diet consumed 16.1
and 10.1% less crude protein and total phosphorus, respectively. The LN diets showed to be
an efficient feeding strategy to reduce the impact of pig production on the variables
appointed as indicators of climate change by about 3.75%. Similar effects were observed
for 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, when
pigs were fed with LN diets. Conversely, cumulative energy demand was not affected by
dietary nutrient reduction. It was concluded that the reduction of crude protein, amino acids
and phosphorus contents to better adjust nutrient supplies to animals requirements appears
very effective for reducing life cycle impact of pig fattening.
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