Life Cycle Assessment of Egg Production: Effects of Breed and Feeding a Low-Protein Diet With Amino Acids During Laying Period.

Feeding low-protein diets supplemented with amino acids to poultry has been implemented to reduce the environmental impacts from excretion, while maintaining productivity. This study conducted a process-based life cycle assessment of egg production to evaluate the effects of breed and feeding low-protein diets (reduced by 2 percentage points in crude protein content) supplemented with amino acids (lysine, methionine, and tryptophan) to layers. The production system was simulated based on a nutrient requirement model and Japanese layer management guidelines. The system boundary was defined as the cradle-to-farm gate, and the environmental impacts were expressed per 1 kg of eggs produced. The environmental impact differences between white egg and brown egg layer breeds were also evaluated. As a result, the environmental assessment showed that feeding low-protein diets reduced the impacts on global warming (by 5%), acidification (by 20%), eutrophication (by 14%), and energy consumption (by 2%), which were mainly caused by decreases in emissions generated from excretion. Compared with white egg layers, brown egg layers had larger environmental impacts due to their higher feed conversion ratio. This study quantitatively demonstrated how feeding a low-protein diet supplemented with amino acids and differences in layer breeds affect environmental impacts.