Effect of supplementation of phytase and its combination with xylanase, amylase, and protease on growth performance, carcass quality and nutrient utilization of yellow-feathered broilers fed diets with lower nutritional density

The addition of exogenous enzyme improved growth performance and nutrient availability in poultry. However, their efficacy in yellow-feathered broilers remained inadequately assessed. This study was conducted to evaluate the effect of phytase (PHY) supplementation alone and its combination with xylanase, amylase, and protease (XAP) on growth performance and carcass traits of yellow-feathered broilers fed diets with lower nutritional density. A total of 800 1-day-old male broilers were randomly allocated into 5 groups with 8 replicates and 20 birds per pen, including positive control (PC) group that received a normal diet meeting the nutrient requirement, negative control 1 (NC1) group with reduced nutrient levels [0.18-0.19 % Ca, 0.17-0.18 % NPP, 0.56-0.59 % CP and then 62-63 kcal/kg AME], NC1 + PHY group, a negative control 2 (NC2) group with reduced nutrient levels [0.18-0.19 % Ca, 0.17-0.18 % NPP, 0.56-0.59 % CP and 105-106 kcal/kg AME], and NC2 + PHY + XAP group. Compared to PC, NC1 and NC2 groups (P < 0.05) reduced final body weight (BW) and average weight gain (ADG), and increased feed/gain ratio (F/G) of broilers during day (d) 1-42 and d 1-56. Dietary enzyme supplementation of phytase alone (PHY) and its combination with XAP (NC2 + PHY + XAP) showed greater improvements on final BW, ADG, and F/G at d 1-56 than NC1 and NC2 groups. However, no significant differences (P > 0.05) were noted between PC and NC1 + PHY groups, nor PC and NC2 + PHY + XAP groups. Dietary nutritional levels and enzyme supplementation had no effect (P > 0.05) on carcass traits and meat quality of yellow-feathered broilers at d 56. Dietary supplementation of phytase alone and its combination with XAP increased (P < 0.05) the digestibility of GE, CP, Ca, P, and some AA compared with NC diets in broilers. In conclusion, dietary reduced nutritional levels impaired growth performance and nutritional values of yellow-feathered broilers during d 1-56, while these adverse effects were eliminated by the supplementation of phytase or in a combination of NSP enzymes.