High-energy diets with reduced digestible lysine for Japanese laying quails under thermoneutral conditions: effects on laying performance, egg quality, and profitability

Abstract Japanese quails ( Coturnix coturnix japonica ) are widely used for commercial egg production, requiring an adequate dietary energy-to-amino acid ratio to support egg production and economic returns. However, current recommendations for laying Japanese quails remain inconsistent due to variations among strains, production phases, and environmental conditions. In this study, the interactive effects between dietary metabolizable energy (ME) and digestible lysine (DL) on laying performance, egg quality, and profitability in quails reared in a climate-controlled environment were assessed. Birds were fed diets formulated to contain three ME levels (2600, 2875, or 3150 kcal/kg) combined with four DL levels (0.90, 1.05, 1.20, or 1.35%) in a 3 × 4 factorial arrangement. Responses were monitored over a 32-week experimental period divided into two consecutive 16-week phases (Phase I: 60 to 172 days; Phase II: 173 to 285 days of age). Compared with lower-ME diets, increasing dietary ME to 3150 kcal/kg improved the laying percentage, egg mass, feed-to-egg ratio, and profitability ( P < 0.05). Conversely, increasing dietary DL above the lowest level tested (0.90%) provided no additional productive or economic benefits, despite ME-dependent interactions affecting eggshell traits and body weight. These findings suggest that, in climate-controlled production systems, Japanese laying quails may benefit from greater dietary energy density than some current recommendations indicate, whereas additional DL supplementation above 0.90% was not associated with consistent improvements in laying performance and profitability. Therefore, high-energy diets formulated with 3150 kcal/kg ME combined with 0.90% DL supported egg production and egg quality while improving feed efficiency and profitability under thermoneutral conditions.