Effects of Graded Crude Protein Levels Under Fixed Amino Acid Supplementation on Growth Metabolism, Slaughter Quality, Nitrogen Emission, and Breeding Efficiency of Small White-Feather Broilers

The suboptimal efficacy of a low-protein diet in small white-feather broilers is due to a lack of alignment with their specific nutritional requirements. To investigate these precise requirements and to promote the application of low-protein diets in these birds’ feeding, we evaluated the effects of graded crude protein (CP) levels under fixed amino acid supplementation in small white-feather broilers. A two-phase feeding trial (1–21 and 22–42 days) was conducted using 480 chicks that were 1 day old, and the experimental diets contained varying CP levels (Phase 1: 18, 19, 20, 21%; Phase 2: 16, 17, 18, 19%) while maintaining constant levels of limiting amino acids. Key findings revealed that Group 3 (Phase 1: 20% CP; Phase 2: 18% CP) exhibited superior early growth performance during days 1–21, with fecal nitrogen excretion reduced by 11% relative to that in Group 4. Additionally, carcass characteristics, serum biochemical parameters, and serum antioxidant capacity were compared across all groups. These findings offer initial insights into the effects of low-protein diets on small white-feather broilers and lay the groundwork for future amino acid optimization studies.