Effects of Dietary Energy and Protein Levels on Growth Performance and Immune Competence of CARI-Nirbheek Chickens in Tropical Environments

Why It Matters

The findings give small‑holder poultry producers a science‑backed feeding roadmap that boosts growth and disease resistance while keeping feed costs in check.

Key Takeaways

• 2,900 kcal/kg ME + 20% CP maximizes starter weight gain.
• 2,700 kcal/kg ME + 16% CP yields best grower phase growth.
• 2,500 kcal/kg ME + 20% CP enhances immune response.
• Feed intake rises with 20% CP; FCR unchanged across diets.
• Serum total protein increases with higher dietary protein.

Pulse Analysis

Backyard poultry remains a cornerstone of rural nutrition and income in many tropical regions. The CARI‑Nirbheek, an improved dual‑purpose breed developed by India’s Central Avian Research Institute, is tailored for these low‑input systems, but its performance hinges on precise nutrition. Energy and protein are the two most influential dietary components, dictating not only growth rates but also the birds’ ability to mount effective immune defenses against endemic pathogens. By systematically varying ME and CP, the researchers generated a detailed performance matrix that fills a long‑standing knowledge gap for small‑scale growers.

The data reveal a clear phase‑specific feeding strategy. During the first four weeks, a high‑energy (2,900 kcal/kg) and high‑protein (20 % CP) diet drives the fastest weight gain, likely because young chicks have elevated metabolic demands for tissue development. As birds transition to the grower phase (weeks 5‑14), a modest reduction in energy to 2,700 kcal/kg paired with slightly lower protein (16 % CP) sustains growth without compromising feed efficiency. Notably, feed conversion ratios remained stable across all treatments, suggesting that the observed gains stem from nutrient adequacy rather than wasteful consumption, an important consideration for cost‑sensitive farmers.

Beyond growth, the study underscores nutrition’s role in immune competence. The strongest phytohemagglutinin‑P and SRBC antibody responses emerged in birds fed the lowest energy level (2,500 kcal/kg) but the highest protein (20 % CP), indicating that protein can compensate for reduced caloric intake in supporting immune function. For rural producers, this translates into a practical recommendation: prioritize protein enrichment when feed budgets limit energy provision. Implementing these phase‑adjusted rations can improve flock health, reduce mortality, and ultimately enhance the profitability and sustainability of tropical backyard poultry enterprises.