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Effects of xylanase on growth performance and digestibility of fiber and energy in growing pigs fed corn, corn DDGS and soybean meal based diet supplemented with phytase
A total of 28 pigs (initial BW 18.5 ± 3.0 kg) were used in a 42-d trial (d 1 to 21 and d 21 to 42 as phase 1 and 2, respectively) to evaluate effects of xylanase (X) on growth performance and nutrient digestibility. Pigs were fed a control diet without or with 2,000 U of X/kg of feed. Each treatment had 7 pens with 2 (a female and a male) pigs per pen. The diets were based on corn, corn dried distillers grains with solubles and soybean meal with 500 FTU of phytase/kg of feed and celite as indigestible marker. Enzymes were provided by Danisco UK Ltd. Pigs had free access to feed and water throughout the trial. Fecal grab samples from each pen were collected during the last 3 d of each phase for apparent total tract digestibility (ATTD) of gross energy (GE) and non-starch polysaccharides (NSP). The assayed xylanase levels in the feed were 2,144 and 2,675 U/kg of treated diets in phase 1 and 2, respectively. The dietary concentrations of the total NSP (11.4 vs. 13.1 %) and arabinoxylans (4.7 vs. 5.9%) in phase 1 and 2, respectively, were comparable. However, phase 1 diets had higher ratio of soluble to insoluble NSP (19.5 vs. 14.7%) and arabinoxylans (6.7% vs. 4.7%) than phase 2 diets. Supplemental X enhanced ADG by 10.4% (805 vs. 729 g/d; P = 0.01) in phase 1 however, X had no effect (P> 0.10) on ADFI, FCR and ADG in phase 2 and during the overall period. In phase 1, X tended to improve ATTD of GE compared to the control (74.6 vs. 72.5%; P = 0.10).The improvements in GE could be explained by the tendency for an improvement in ATTD of total NSP (47.3% vs. 42.0%; P = 0.08), arabinose (49.9% vs.44.5%;P =0.05), galactose (63.8 vs. 59.9%; P = 0.06) and glucose (51.8vs.46.8%; P = 0.10) compared to the control mainly due to improvement (P < 0.05) of ATTD of the corresponding constituent sugars in the insoluble NSP fraction. In phase 2, X had no effect on ATTD of GE but increased ATTD of mannose (83.5 vs. 79.6%; P = 0.01) and tended to improve ATTD of rhamnose (53.0vs. 42%; P = 0.08) in the soluble NSP fraction. In conclusion, xylanase improved fiber utilization and hence energy digestibility and growth performance in growing pigs, however in this study the response was only evident in the first 21 d of feeding.
Keywords: xylanase, phytase, digestibility, growth performance, pigs