| Three trials were conducted to investigate the effects of xylanase supplementation on the performance, nutrient utilization, and development of digestive tract, immune organs,tibia parameters in broilers and examine the interaction between xylanase and phytase in poultry diets.Trial one The trial was conducted to study the effects of different levels of xylanase on the performance, nutrient utilization, digestive tract and immune organs measurements and tibia parameters in broilers fed wheat-based diets. Two hundred and forty 1-d-old Arbor Acres broilers were allocated to 4 dietary treatments(with 5 replicate pens of 12 chicks each) in a randomized complete block design. A wheat-corn-based basal diet containing 40% wheat was designed with 0, 500, 1000, 5000 U/kg xylanase supplemented. Xylanase improved feed efficiency significantly(P<0.05) and had no significant effects on feed intake and body weight gain of broilers during 1-21 d, 22-42 d and 1-42 d(P>0.05). Supplementing xylanase improved the apparent dry matter digestibility(P=0.093)and AME (P=0.110)of 1-21 d , and the apparent digestibility of crude protein , Ca and P was not significantly improved by xylanase supplementation in 1-21 d and 22-42 d (P>0.05). No significant differences were observed in the fecal moisture among the groups in both 1-21 d and 22-42 d(P>0.05). Supplementation of 1000 U/kg xylanase decreased the relative length of ileum significantly of 21 d old broilers and xylanase supplementation decreased the relative length of jejunum of 42 d old broiler(sP<0.05). Xylanase supplementation had no significant effects on the relative weight of duodenum, jejunum, ileum and the whole intestine(P>0.05). Xylanase supplementation decreased the relative weight of spleen of 21 d (P=0.083)and had no effects on the weight of gizzard and pancreas(P>0.05). 500 U/kg xylanase decreased the relative weight of glandular stomach significantly(P<0.05), and weight of gizzard of 1000 U/kg xylanase treatment was significantly higher than 500 U/kg (P <0.05). No significant differences were observed in the weight of spleen, liver and abdomen fat among groups(P>0.05). Supplementation of xylanase tend to decreased the Ca content (P=0.096)of the tibia at 21 d and the tibia length (P=0.097)at 42 d of the broilers , and xylanase tend to increased the tibia weight(P=0.074)of broilers at 42 d. No significant differences were observed among different levels of enzyme treatments(P>0.05). These data indicated that 500 U/kg xylanase improved feed conversion of broiler significantly and increasing to 5000 U/kg (5-10 times of industry recommendation) result in no significant additional or negative response.Trial two This study was conducted to investigate the effects of different levels of xylanase and phytase supplementation, individually or in combination, on the nutritive value of wheat-based diets with a 4×4 factorial designs. The experimental diets consisted of a basal diet with 40% wheat supplemented 0, 1000, 2000 or 3000 U/kg xylanase and 0, 200, 400 or 600 U/kg phytase. Thirty-four 22-week-old Lohmann Brown roosters were randomly distributed to treatments with two roosters each for four turns using TME methods. Supplementation of xylanase and phytase alone tend to increase TME and the true utilization of true protein(P>0.05). Supplementing xylanase alone can increase the utilization of phytate (P<0.05), and supplementing phytase alone increased utilization of phytate significantly (P<0.05). Different levels of xylanase and phytase, supplemented alone or in combination, had no significant effects on the true values of crude protein, calcium and total phosphorus (P>0.05). There were no interactions between xylanase and phytase on the nutritive values except the utilization of true protein (P>0.05). No significant effects were observed among treatments with different levels of enzymes and their combinations. The study indicated that the levels of xylanase supplemented in wheat-based diets should be lower with phytase supplementation than supplemented alone. In general, no negative interactions between xylanase and phytase were found, indicating that both types of enzymes may be used in feed based on wheat.Trial three The study was conducted to examine the effects of xylanase and phytase and their combination on the utilization of diets for poultry with a 2×2×2 factorial design. The experimental diets contained a P-adequate basal diet and a P-deficient basal diet. Both diets were supplemented with 0, 1000 U/kg xylanase and 0, 400 U/kg phytase. Seventy-two 22-week-old Lohmann Brown roosters were randomly distributed into nine groups with four replicates each and two roosters in each replicate using TME methods. Supplementation of xylanase, phytase and their combination had no effects on TME and the true value of protein, total phosphorus and phytate in P-adequate diets, addition of xylanase individually tend to increase the true utilization of calcium(P>0.05). To the P-deficient diets, supplementation of xylanase, phytase and their combination had no effects on TME and the true value of protein, Supplementing xylanase individually tend to increase the true utilization of calcium, total phosphorus and phytate(P>0.05), phytase tend to increase the true utilization of calcium(P>0.05) and increased the true digestibility of total phosphorus and phytate significantly (P<0.05), xylanase and phytase supplemented in combination improved the true utilization of phytate significantly(P<0.05). Interactions between xylanase and phytase were observed in the true utilization of calcium only. The study suggested that phytase played a main in P-deficient corn-based diets and xylanase may inhibit the effects of phytase via increasing the digestibility of Ca.In conclusion, suitable level of enzyme supplemented in diets with 40% wheat was 500 U/kg in the condition of present trail, and supplementing excess xylanase had no additive or negative effects on the performance, nutrient utilization and gastrointestinal development of broilers. No significant interaction between xylanase and phytase in nutrient true values were observed in wheat-based and corn-based diets, and phytase play a main role in the phosphorus digestibility in P-deficient diets and excess xylanase may inhibit the effects of phytase by releasing more Ca to the digestive tract.
|
PDF Full Text Request