Effects Of Protease And Xylanase On Performance, Digestive Function And Blood Parameters Of Broilers

With protease and xylanase as the representative of endogenous and exogenous enzymes, this experiment was conducted to investigate the mechanism of these two kinds of enzymes through observing the effects of different levels of protease and xylanase on performance, digestive function and blood parameters on broilers in order to provide theoretical foundation of reasonable application of enzymes in poultry diets. Nine hundred and seventy two 1-day-old Cobb 500 broilers were randomly divided into 9 treatments, with 9 replicates of 12 broilers each. The wheat-based diets were supplemented with 0, 4000, 32000 U/kg protease and 0, 1000, 8000 U/kg xylanase using a 3x3 factorial design. The experiment periods were starter phase (1 to 21 d) and grower phase (22 to 42 d).The results showed that supplementation of 4000 U/kg protease +1000 U/kg xylanase significantly decreased the feed intake (P<0.05); Level of 32000 U/kg protease tended to increase the feed intake of 1 to 21 days broiler chicks (P =0.080) and significantly increased the weight gain of 22 to 42 days broiler chicks (P<0.05), but still didn't show any effects on FCR (P>0.05).Protease and xylanase supplementation had no effects on the digestive organs indices of broiler chicks (P>0.05); Level of 1000 U/kg xylanase and 8000 U/kg xylanase tended to increase the index of ileum of 1 to 21 days broiler chicks (P =0.051).Level of 8000 U/kg xylanase significantly increased the activities of lipase and trypsin of 22 to 42 days broiler chicks (P<0.05), and increased the activities of amylase of 1 to 21 days and 22 to 42 days broiler chicks by 9.87% and 6.82%. Level of 32000 U/kg protease significantly decreased the activities of lipase of 1 to 21 days broiler chicks (P<0.05), tended to decreased the activities of lipase of 22 to 42 days broiler chicks (P=0.091) and decreased the activities of amylase of 1 to 21 days and 22 to 42 days broiler chicks by 8.75% and 28.14%.Main effect of 1 to 21 days broiler chicks showed that level of 32000 U/kg protease tended to decrease the villus height of duodenum (P=0.111) and jejunum (P=0.081) and significantly decreased the ratio of villus height to crypt depth of duodenum and ileum (P<0.05). Level of 8000 U/kg xylanase significantly decreased the crypt depth of duodenum (P<0.05), increased the ratio of villus height to crypt depth of duodenum (P<0.05) and the villus width of jejunum (P<0.05) and tended to decrease the muscle thickness of ileum (P=0.065). Level of 4000 U/kg protease and 1000 U/kg xylanase significantly decreased the muscle thickness of jejunum (P<0.05). Main effect of 22 to 42 days broiler chicks showed that level of 4000 U/kg protease significantly decreased the crypt depth and muscle thickness of duodenum, jejunum and ileum (P<0.05). Level of 32000 U/kg protease significantly decreased the villus height and the ratio of villus height to crypt depth of duodenum, jejunum and ileum (P<0.05). Level of 1000 U/kg xylanase and 8000 U/kg xylanase significantly decreased crypt depth of duodenum, jejunum and ileum (P<0.05), and significantly increased the ratio of villus height to crypt depth of duodenum, jejunum and ileum (P<0.05). Level of 8000 U/kg xylanase significantly decreased the muscle thickness of jejunum (P<0.05).Supplementation of 32000 U/kg protease significantly decreased the contents of blood glucose of 1 to 21 days broiler chicks (P<0.05); Supplementation of 1000 U/kg xylanase, 8000 U/kg xylanase and 4000 U/kg protease +1000 U/kg xylanase significantly decreased the contents of uric acid of 22 to 42 days broiler chicks (P<0.05); Level of 32000 U/kg protease significantly decreased the contents of blood glucose of 1 to 21 days and 22 to 42 days broiler chicks (P<0.05); Level of 1000 U/kg xylanase and 8000 U/kg xylanase significantly decreased the contents of uric acid of 22 to 42 days broiler chicks (P<0.05).It can be concluded that appropriate level of protease (4000 U/kg) and xylanase (1000 U/kg) improved the digestive function and blood parameters. Excess level of xylanase(8000 U/kg) had no negative effect on performance, digestive function and blood parameters, and even had significantly positive effect on intestinal morphology while excess level of protease(32000 U/kg) had negative effects on digestive enzyme activities, intestinal morphology and blood parameters. It is suggested that there is difference between these two kinds of enzymes.