Effects of supplementing low-energy and/or protein diets with xylanase and protease on broiler chicken growth performance, nutritional utilization, blood biochemical parameters, and gene expression associated with growth

A total of 560 male broilers were divided into 7 groups. 1) a basal diet as a positive control, 2) a low-energy diet (NC) 1) ME content was reduced by 100 kcal/kg compared to PC; 3) a low-protein diet (negative control 2; CP content was lowered by 1% compared to PC); and 4) a low-energy and CP diet (negative control). 3 In comparison to PC, 3 (NC3) ME content was lowered by 100 kcal/kg, while the CP was lowered by 1%. NC2 + 100 g/ton protease (NC2 + 100Pro), NC3 + 100 g/ton xylanase and 100 g/ton protease (NC3 + 100Xyl + 100Pro), and NC1 + 100 g/ton xylanase (NC1 + 100Xyl) are the next three options. Body weight was decreased by feeding NC diets (P < 0.05); on the other hand, feed intake was significantly increased (P < 0.05), thus feed conversion was increased compared to PC. Gizzard, breast, and carcass yield were increased by feeding PC+ enzymes. Moreover, plasma creatinine was decreased by feeding low-CP diets supplemented with or without Xyl and Pro (P ˂ 0.05) when compared with PC and NC1, but neither the muscle fatty acid profile nor blood parameters were affected by the treatments. The addition of enzymes to the NC diet resulted in an increase in the shorter intestinal villi and reduced hepatic IGF mRNA expression in the NC groups. In conclusion, broiler performance was negatively impacted by low-ME and CP diets, although performance, crude protein, fiber and ether extract utilizations, intestinal histology, and growth-related gene expressions were positively impacted by Xyl and Pro supplementation treatments.