Abstract
BACKGROUND: The current broilers have been greatly optimized for weight gain and breast yield, which necessitates the provision of nutrients-dense diets for maximum potential. OBJECTIVES: The current study aimed to evaluate the effect of finisher diet nutrients density (ND) on energy and protein efficiency, productive and economic performance and breast meat quality of broilers raised until different slaughter age. METHODS: A total of 600 23-day-old broiler male chicks (Cobb-500) were assigned to 10 treatments with six replicates and 10 birds each. Experimental treatments were included factorial arrangement of five increment (2.5%) levels of finisher diet ND (92.5%, 95%, 97.5%, 100% and 102.5% as strain recommendation) and slaughtered at 38 or 46 days of age. The relative difference in the energy level of experimental diets was used to increase ND levels at the same ratio. RESULTS: Feed intake (FI) and breast meat quality traits exception water holding capacity (WHC) were not affected by finisher diet ND. In response to increasing finisher diet ND, energy and protein efficiency, productive traits, bio-economic index (BEI) and breast relative weight (BRW) linearly improved. However, residual feed intake and breast meat WHC improved with a quadratic trend. By using broken-line regression analysis, the optimum dietary ND was obtained at 97.5%-102% of strain recommendation. Energy and protein efficiency, feed conversion ratio and BEI deteriorated by prolonging rearing period. The BRW, meat lightness (L*), redness (a*), hue angle (h*) and WHC values for the birds slaughtered at 46 days of age were significantly higher, and cooking loss was lower than those slaughtered at 38 days old. CONCLUSIONS: Broilers during the finisher period are not able to regulate their FIs with diet ND. The energy and protein efficiency, productive and economic performance were reduced when broilers were fed diluted diet or the rearing period was prolonged.