237
Effect of combined xylanase and phytase supplementation on growth performance, carcass characteristics, and apparent total tract digestibility in pigs fed corn-based diets containing multiple by-products
Phytate has been shown to be an anti-nutrient and that feeding high levels of phytase can breakdown phytate improving nutrient utilization and pig performance. Dietary xylanase targets arabinoxylan breakdown improving energy utilization in pigs. However, the individual effects of simultaneous supplementation have not been clearly determined. Crossbred pigs (n=45; mean initial weight: 26.4 kg) were allotted to 9 treatments to evaluate the effect of both xylanase (Econase XT; endo-1,4-beta xylanase [EC 3.2.1.8]) and phytase (Quantum Blue) supplementation as follows: 1) positive control [PC]: a corn-SBM based diet with 15% each of corn distillers dried grains with solubles, and wheat middlings and 13% of corn germ meal, 2) negative control [NC]: ME was reduced by 103 kcal/kg from the PC diet by replacement of fat with corn starch in each of the 4 feeding phases, 3) NC + phytase (500 FTU/kg diet), 4) NC + phytase (1,000 FTU/kg diet), 5) NC + phytase (2,000 FTU/kg diet), 6) NC + xylanase (24,000 BXU/kg diet), 7) NC + phytase (500 FTU/kg diet) + xylanase (24,000 BXU/kg diet), 8) NC + phytase (1,000 FTU/kg diet) + xylanase (24,000 BXU/kg diet), 9) NC + phytase (2,000 FTU/kg diet) + xylanase (24,000 BXU/kg diet). All diets were formulated to meet nutrient requirements before phytase and xylanase addition to the diets. Body weight and feed consumption were recorded to calculate growth performance, and pigs were ultrasonically scanned at the end of the experimental period to measure fat and loin depth. Fecal collection was performed in the final phase for 3 consecutive days to estimate apparent total tract digestibility (ATTD). There were no significant interactions between xylanase and phytase supplementation on growth performance, carcass characteristics and ATTD. Xylanase supplementation showed a nonsignificant numerical response in gain (+1 kg) and G:F ratio (+0.007). However, ADG (P < 0.01, quadratic) and G:F ratio (P = 0.04, linear) for the overall period increased as phytase levels increased. Carcass lean percentage and lean gain increased (P < 0.05; linear) as phytase levels increased. The ATTD of DM, NDF, ether extract (P < 0.05), and hemicellulose (P = 0.05) increased quadratically as phytase level increased. The ATTD of P increased as phytase supplementation levels increased (P< 0.05, linear and quadratic). These results indicate that the improved nutrient digestibility, performance and carcass response to phytase supplementation is beyond P provision. However, xylanase usage alone or with phytase requires continued evaluation.
Keywords: phytase, pigs, xylanase