Assessment of the environmental impacts of EU broiler chicken production depending on the reduction of dietary protein-to-energy ratio and geographical origin of soybean

The energy and protein requirements of modern broiler chickens are generally met throughout the provision of balanced commercial diets with optimal protein-to-energy ratios. The availability of EU soybean, the main protein source in poultry feeding, is a critical aspect being the amount of it not sufficient to meet domestic demand making the EU strongly dependent on imports from Latin America and the US. The present study aimed to quantify the environmental impacts of broiler meat production according to the crude protein-to-metabolizable energy ratio and the geographical origin of soybean. A total of 600 one-day-old male Ross 308 chicks (n=300/group) were fed a conventional basal diet (CON) or the same diet with a 10% lower crude protein content (LOW) using EU soybean. The birds were slaughtered at 34 days age (body weight: 2,429 ± 54 g) and LCA was applied to assess the environmental implications according to the tested experimental factors. Acidification (AP) and eutrophication (EP) potentials were assessed using the CML-IA baseline method, while the global warming potential (GWP) was calculated through the ReCiPe 2016 midpoint (H) method. The analysis was conducted on a cradle-to-farm gate basis considering the functional unit (FU) = 1 kg of live bird weight (LW) and on a cradle-to-plant gate basis when the FU was 1 kg of breast meat (BM). Then, two scenarios were hypothesized comparing soybean imported from Brazil (#1) or US (#2). The use of CON or LOW diets and EU soybean did not affect the selected impact categories at farm gate. Otherwise, the use of LOW diet slightly increased (+5/14%) the impact categories when BM was considered. Independently of FU, scenario #1 consisted in an increase of +24/30% of GWP and +15/26% of the AP, whereas a reduction (-10/15%) was observed for the EP. However, in case of utilization of US soybean, an increase of all impact categories was detected both for CON and LOW diets and FUs (GWP: +10/17%; AP: +42/52%; EP: +6/12%). In conclusion, the reduction of crude protein-to-energy ratio did not influence the considered impact categories at farm gate, while worsened the environmental impacts for 1 kg of BM at plant gate. Overall, the use of EU soybean represents the most environmentally sustainable choice for EU broiler meat production; indeed, the import of soybean from overseas results in an increase of GWP and AP impact categories.