Comparative efficacy of xylanases on growth performance and digestibility in growing pigs fed wheat and wheat bran- or corn and corn DDGS-based diets supplemented with phytase

Two experiments were conducted to determine the effects of supplemental xylanases on growth performance, coefficients of apparent ileal (CAID) and total tract (CATTD) digestibility in growing pigs fed wheat- or corn -based diets. Two basal diets were formulated based on either corn plus 40% corn distillers dried grains with solubles or wheat plus 25% wheat co-products and fed without or with five xylanases from different microbial origins. The xylanases were identified as A, B, C, D and E and fed at 75mg of xylanase protein/kg of feed. All diets contained added phytase. In Experiment 1, the diets were offered for 42 d to 96 individually penned gilts (29.0±0.2kg) to give 8 pigs per diet. An interaction between diet type and xylanase was observed for ADG (P<0.05) such that pigs fed wheat diets with xylanases A and C and corn diets with xylanases A and D had greater (P=0.044) ADG than pigs fed xylanase-free diets or wheat diets with xylanase D or corn diets with xylanases B and C. A main effect of xylanase was observed for G:F in which case xylanase A improved G:F by 10% (P=0.010) compared to the control. In Experiment 2, TiO2 (3g/kg) was added in all diets and pigs were allotted diets in a Youden Square design, to give 6 replicates per diet. Interaction (P<0.05) between diet type and xylanase were observed on CAID of gross energy (GE), insoluble arabinose and xylose (iAX), total arabinose and xylose (tAX), insoluble NSP (iNSP), and total NSP (tNSP). In this context, pigs fed wheat-based diets with xylanase C and D and those fed corn-based diets with xylanases B and E had greater (P<0.05) CAID of GE compared to those fed xylanase-free diets. The CAID of tAX and tNSP in pigs fed wheat-based diets with xylanase C and corn-based diets with xylanases B and E were higher (P<0.001) than in pigs fed the other diets. There was no treatment effects on CATTD of GE, DM and crude protein, however, xylanases independently improved (P=0.040) CATTD of fat compared to the control. Different xylanases responded differently in improving dietary components digestibility and growth performance depending on the diet type. However, the comparisons made in the present study are only valid for the test conditions as some of the xylanases may have been dosed at levels below the biological optimum and others well above.