Evaluating the impact of reduced-protein diets with varying ingredient combinations on broiler chickens’ performance, body composition and nutrient utilization

Ingredient availability is a factor that could impact nutrient utilization and consequently broiler performance, especially when feeding reduced crude protein (CP) diet. In this study, 2304 male Ross 308 broiler chicks were allotted into nine treatments in a 3 × 3 factorial arrangement. All birds were offered a common starter diet from 0 to 7d. On d8, they were assigned to treatments in groups of eight replicates of 32 birds each. The experimental diets were formulated based on three cereal combinations – corn; wheat-corn; sorghum-wheat, each of three CP levels: control CP, 20 g/kg CP reduction (LCP20), and 40 g/kg CP reduction (LCP40). The CP levels of 230, 210, and 190 g/kg (grower I); 215, 195, and 175 g/kg CP (grower II); and 205, 185, and 165 g/kg (finisher) were maintained. The feed conversion ratio (FCR) was similar and superior in broilers fed the control and LCP20 diets during the early growth phase (8–28 days) but worsened during the finisher phase. Protein and fat intake declined with lower CP level. Fat deposition increased while nitrogen (N) excretion reduced with lower CP levels. Corn-based diets had highest carcass weight and breast yield at all levels of CP. Wheat-corn and sorghum-wheat diets gave similar results up to 20 g/kg CP reduction. Amino acid (AA) digestibility increased as dietary protein reduced. Broilers fed wheat-corn or sorghum-wheat diets showed lower but comparable body weight gain (BWG), and up to 20 g/kg CP reduction, BWG was unaffected regardless of diet composition. However, broilers on corn-based diets demonstrated improved FCR. These findings suggest that wheat-corn or sorghum-wheat diet may yield similar performance to corn in broilers when dietary CP is reduced up to 20 g/kg.