A trial was conducted to study the influence of different levels of a commercial enzyme complex on performance, nutrient availability, blood parameters, digestive tract measurements, amylase and trypsin activity of the digestive tract and gut morphology in broilers fed the typical diets in north China. There were four treatments: the control diet and the other three enzyme complex supplemented diets which were 180 mg/kg, 360 mg/kg and 720 mg/kg enzyme complex supplemented to the control diet, respectively. The birds fed the diets supplemented with 180 mg/kg and 360 mg/kg enzyme complex had better performance and nutrient availability, the activities of amylase and trypsin in the digestive tract in the two treatments were improved, the villus height and surface area of villus in the small intestine increased and the crypt depth and epithelial thickness of small intestine decreased. Relative weights of pancreas and relative weights and lengths of small intestine decreased. However, the addition of 720 mg/kg enzyme complex had no effects on these parameters and increased crypt depth and epithelial thickness of the small intestine. The data suggested that suitable supplementation of enzyme complex was beneficial for the birds, while excess enzyme complex inhibited secretion of endogenous enzyme and destroyed the structure of the small intestine.

Two experiments were conducted with broilers to investigate the feasibility of microbial phytase replacing partial inorganic phosphorus supplementation and the synergistic effects of xylanase (320 FTU/kg) supplementation alone or in combination with phytase (750 U/kg) replacing 0.08% dietary inorganic phosphorus, on the growth performance and utilization of nutrients in broilers fed wheat-based diets. In Experiment 1, 540 broilers were fed five diets for 6 weeks. Diets C0 and C1 were corn-based diets and 0.08% inorganic P supplementation was replaced with 750 U phytase/kg feed in Diet C1. Diets W0, W1 and W2 were wheat-based diets supplemented with microbial phytase 0, 750, 750 U/kg feed and 0, 0.08% and 0.16% dietary inorganic P were replaced, respectively. In Experiment 2, 432 broilers were divided into four treatments to determine the synergistic effects of supplemental xylanase and phytase replacing 0.08% inorganic P. Four experimental diets were arranged according to a 2×2 factorial design. The results indicated that addition of phytase increased the digestibility of phytic P by 31.0 to 55%, dramatically decreased the excretion of phytic P and total P by 31.6 to 55.0% and 13.8 to 32.9%, respectively (p<0.01). It is feasible to completely replace 0.08% inorganic phosphorus supplementation with microbial phytase 750 U/kg in corn-or wheat-based diets for broilers. Addition of xylanase alone or in combination with phytase replacing 0.08% dietary inorganic P, increased body weight gain and feed utilization efficiency of broilers fed wheat-based diets (p<0.10) and decreased overall mortality (p<0.10). In the groups of birds supplementing xylanase 320 FTU /kg feed, a marked elevation of the dietary AME was observed (p<0.05). Addition of phytase replacing 0.08% dietary inorganic phosphorus, concurrently with xylanase supplementation had additive effects on the apparent digestibility of dietary phytic P and overall feed conversion ratio (p<0.05).

Two experiments were conducted to examine the effects of dietary inclusion of xylose on growth performance, nutrient digestibility and xylose absorption in the portal-drained viscera of broiler chicks. In Exp. 1, ninety male 14 day-old broilers were used to study the effects of different inclusion levels (0, 5, 10, 20 and 40%) of D-xylose in the semi-purified diets on the growth and nutrient digestibility of broilers. In Exp. 2, One hundred and eight male broilers, fed by precision feeding at 22 day-old, were used to investigate the absorption and transportation of dietary xylose in the portal-drained viscera of broiler. The results of Exp. 1 indicated that the growth of broilers was gradually decreased as the xylose level increased (p<0.01). With the xylose supplementation increased, the moisture in broiler excreta was gradually elevated (p<0.01), AME and the digestibilities of crude protein and ether extract were significantly reduced and the digestibilities of xylose and arabinose were also decreased (p<0.01). The results of Exp. 2 showed that the concentrations of ribose, xylose and galactose in serum were significantly influenced by different dietary levels of xylose (p<0.01), but there's no apparent difference among rhamnose, glucose and arabinose (p>0.05). The xylose concentration in serum was highest in Vena Cava, middle in Portal Vein and lowest in Ulnar Vein within 6 h after precision feeding. And then the xylose concentration in Portal Vein and Ulnar Vein were higher than that of Vena Cava. The concentration of ribose, xylose and galactose in serum were also significantly changed with time prolongation (p<0.01). The concentration of xylose in serum was highest in the 40% xylose treatment, middle in the 20% xylose group and lowest in the control group. The glycogen contents in liver and muscle were linearly decreased as the level of xylose increased (p<0.01). The higher the dietary level of xylose was, the lower digestibility of dietary xylose was (p<0.10). 40% xylose markedly decreased the digestibility of dietary glucose (p<0.01). In conclusion, high levels of xylose in the diets inhibited the growth and nutrient digestibility of broiler. The outputs of xylose from the hydrolyzation of wheat-based diet by xylanase should have no adverse effects on broiler performance.