Effects of dietary protein-energy ratios on growth performance, metabolic parameters, endocrine profiles, and carcass traits in growing rabbits maintained under tropical conditions at Ahmadu Bello University, Zaria.

Background Tropical climates impose significant heat stress on growing rabbits, disrupting metabolic-endocrine regulation and compromising growth performance when dietary protein-energy ratios are suboptimal. This study was conducted to evaluate the effects of five dietary protein-energy ratios on growth performance, metabolic parameters, endocrine profiles, and carcass traits in growing rabbits maintained under tropical conditions at Ahmadu Bello University, Zaria. Materials and Methods Five dietary protein-energy ratios (14% CP/2800 kcal ME/kg, 15% CP/2700 kcal ME/kg, 16% CP/2600 kcal ME/kg, 17% CP/2500 kcal ME/kg, and 18% CP/2400 kcal ME/kg) were formulated and provided to 100 growing rabbits (New Zealand White × local cross) under natural tropical conditions at Ahmadu Bello University, Zaria, Nigeria. The experiment employed a completely randomised design with four replicates per treatment over 56 days. Data collected and generated were subjected to one-way analysis of variance (ANOVA) with means separated using Tukeys’ HSD Test. Results The medium-high ratio (17% CP, 2500 kcal ME/kg) significantly improved final body weight (2485 g), average daily gain (32.8 g/d), and feed conversion ratio (2.70) compared with lower ratios. Serum total protein (68.5 g/L) and albumin (38.0 g/L) increased while urea (6.2 mmol/L) and triglycerides (1.05 mmol/L) decreased. Anabolic hormones rose markedly (insulin 18.5 µIU/mL, IGF-1 215 ng/mL) alongside elevated thyroid hormones (T3 2.45 nmol/L, T4 60.4 nmol/L) and reduced cortisol (19.8 nmol/L). Dressing percentage (63.4%) and hot carcass weight (1575 g) were highest, with lower liver relative weight (3.1%). Lower ratios induced catabolic shifts, impaired nutrient utilisation, and reduced performance. Conclusion The results indicate that protein-energy ratios of 17–18% CP and 2400–2500 kcal ME/kg optimise metabolic efficiency, endocrine homeostasis, and lean tissue accretion in tropical rabbit production using local feed resources.