Comparison of the environmental impacts of chicken meat production among fast-, medium- and slow-growing genotypes fed diets with different protein-to-energy ratio

In next few years, the European chicken meat production could change remarkably due to the adoption of the Better Chicken Commitment (BCC) requirements. This study aimed to assess the environmental implications of using some BCC-approved genotypes when fed different dietary regimens. A total of 1,800 one-d-old male chicks of three genotypes (n=600/genotype), i.e. fast- (FG), medium- (MG) and slow-growing (SG) exhibiting an average growth rate of >70, 40-50 and 30-40 g/d, respectively, were fed 3-phase basal diet (starter, grower, finisher) with two crude protein (CP)-to-energy ratios, i.e. conventional (CON; 22.5, 20.5, 18.5%) and 10% lower CP content (LOW; 20.3, 18.3, 16.5%). FG, MG and SG were slaughtered at 34, 50 and 77 days, respectively, at a similar range of commercial weight for medium-size broilers. Life Cycle Assessment (LCA) was conducted from cradle-to-abattoir and the functional unit was 1 kg of eviscerated carcass. Primary data on growth performances and slaughtering yields were collected, and N excretion was calculated as the difference between N input (i.e., N from feed and day-old chick) and N retained in the body at slaughter age. Power energy consumption was based on literature sources, while manure CH4, N2O and NH3 emissions were calculated according to FAO LEAP guidelines. Data were modelled on OpenLCA 2.0.2 and the considered impact categories were global warming (GWP, kg CO2 eq), calculated through the ReCiPe 2016 midpoint (H) method, acidification (AP, kg SO2 eq) and eutrophication potentials (EP, kg PO43- eq), obtained according to the CML-IA baseline method. The effects of genotype under the same feeding program and diet in each genotype were investigated. For both feeding programs, the FG contributed less to all environmental indicators, while the SG was identified as the most impactful, having a GWP 2.5 times higher than FG and presenting a substantial increase of both AP (+80/85%) and EP (+80/95%). The MG showed intermediate impact values, with an increase of GWP (+40%), AP and EP (+25/30%) compared to FG. When the effect of diet was considered, minor differences were observed for all the impact categories. In example, it was estimated that GWP can be slightly reduced by adopting LOW program in MG (-0.2%) and SG (-2.4%) compared to CON. In conclusion, chicken meat production with MG and SG genotypes had negative effects on the selected impact categories, whereas the adoption of feeding programs matching their nutritional requirements could enhance sustainability traits.