Low protein diet with amino acid supplementation maintains laying performance and egg quality while reducing ammonia emissions in Hy-line brown hens.

Ammonia (NH₃) emission from commercial poultry farms significantly contributes to atmospheric pollution, highlighting the need for effective mitigation strategies. This study investigated the effects of a low crude protein (CP) amino acid-balanced diet on performance, egg quality, nutrient digestibility, and excreta gas emissions in laying hens. A total of 252 Hy-line brown laying hens (43 weeks old) were randomly assigned to one of three dietary treatments for 12 weeks: 17% CP (control, CON), 16% CP (low protein, LP), and 16% CP supplemented with amino acids (LPS). The LPS diet was fortified with methionine, lysine, threonine, and tryptophan, to match the amino acids (AAs) profile of the CON diet. Body weight was recorded at start, 2nd, and 12th weeks, while egg production and quality were analyzed weekly. Fecal samples collected in the 7th week were evaluated for nutrient digestibility and gas emission. Reducing dietary CP from 17 to 16% significantly decreased egg production and feed conversion ratio (FCR) during the later weeks (weeks 5 to 12 and 7 to 12, respectively), whereas the LPS diet-maintained performance comparable to the CON group. Egg quality traits, including eggshell color, Haugh unit, yolk color, albumin height, eggshell strength, and eggshell thickness, were unaffected by dietary treatments. Nutrient digestibility (dry matter, nitrogen, gross energy, calcium, phosphorus) remained unchanged. Notably, the LPS diet significantly reduced NH₃ emissions from excreta, while hydrogen sulfide (H₂S) emissions were unaffected. These findings demonstrate that reducing dietary CP with supplemented AAs can effectively mitigate NH₃ emissions without compromising production performance or egg quality in Hy-line brown laying hens.