We measured environmental gas emission during the composting of manure of layers from 200 to 300 days of age fed diets with 2% lower crude protein (CP) when compared with a conventional 19% CP diet. The layers fed CP 19% diet and those fed CP 17% diet showed no difference in the egg-laying rate, egg weight, feed intake, and amount of excreta. However, the layers fed CP 17% diet showed a decrease in nitrogen excretion compared with the layers fed CP 19% diet. Furthermore, environmental gas emission during the composting of manure of the layers fed CP 17% diet for 40 days was reduced as follows : 12.0% for N2O, 49.9% for CH4, and 34.8% for NH3 compared with the manure of the the layers fed CP 19% diet. The concentration of nitrogen, phosphate, and potassium ; carbon-to-nitrogen ratio ; and germination percentage of Komatsuna on the manure of the layers fed CP 19% diet and the layers fed CP 17% diet were similar to those of the manure of layers in Japan. These results indicate that feeding 2% lower CP diets to layers from 200 to 300 days of age did not affect egg productivity and decreased environmental gas emission during composting of their manure Nihon Chikusan Gakkaiho 92 (4), [485][486][487][488][489][490][491] 2021

We fed 330–545 day‐old laying hens (later laying period) a low‐protein diet supplemented with essential amino acids (LPS) and composted their manure. We then investigated the laying performance of the hens, the nitrogen balance and emission of nitrous oxide (N2O), methane (CH4), and ammonia (NH3) from the composting, and several characteristics of the finished compost. There were no significant differences in the egg‐laying rate, egg mass, egg weight, proximate compositions in egg yolk and egg white, or feed intake between the laying hens fed a Control diet (Cont) and those fed the LPS diet. However, the LPS‐fed hens had lower excreta levels and nitrogen excretion. In addition, the environmental gas emissions per layer from composting of the manure from the LPS‐fed laying hens were decreased by 9.7% for N2O, 40.9% for CH4, and 24.8% for NH3 compared to the Cont‐fed laying hens. The concentrations of total nitrogen in the finished compost were similar between the LPS‐fed and Cont‐fed laying hens. In a vegetable‐growth test, the weights of komatsuna plants grown with compost from LPS‐fed and Cont‐fed hens were also not significantly different. Feeding an LPS diet to 330–545 day‐old laying hens was suggested to reduce environmental gas emissions from manure composting without affecting the egg production performance.