Optimising Energy-to-Protein Ratio in Practical Reduced-Protein Diets for Laying Hens

This study evaluated the optimal energy-to-protein ratio in practical reduced-protein diets to evaluate the production performance, nutrient digestibility, and egg quality parameters of laying hens between 20 and 35 weeks of age. The best feed conversion ratio (FCR) of 2.548 was achieved at 15.5% crude protein (CP) and 100% recommended apparent metabolizable energy (AME) level with a reduced-protein diet, followed by 14% CP and 95% recommended AME levels (2.634) from 20 to 35 weeks of age (WOA) (p < 0.05). The yolk index was reduced only in diets containing 17% CP at 90% AME levels (p < 0.01) at week 35. Reduced dietary protein from 17% to 14% decreased egg weight and body weight gain between 20 and 35 WOA (p < 0.05) as well as decreased hen weight and shell breaking strength at 35 WOA (p < 0.05). However, it also reduced nitrogen excretion by 30% (p < 0.001) and increased protein digestibility by 17% (p < 0.01). Between 20 and 35 weeks of age, reducing dietary energy from 100% to 90% AME increased feed intake (p < 0.001), while excreta moisture, dry matter digestibility, and energy digestibility decreased at week 35 (p < 0.001). At week 27, reducing energy from 100% to 90% AME increased shell weight (p < 0.05), whereas lowering protein from 15.5% to 14% increased shell proportion (p < 0.05). Thus, it can be concluded that reducing dietary protein level from 17% to 15.5% with a 100% recommended AME level is optimal to improve feed efficiency while maintaining egg quality in laying hens from 20 to 35 WOA.