Performance and total-tract digestibility responses to exogenous xylanase and phytase in diets for growing pigs

Sixty individually housed male pigs (Large White X Landrace, average weight 19.7±0.56 kg) were used in a completely randomised block design having five wheat-based dietary treatments (n=12 pigs per treatment) to study the interactive effects between added xylanase (XYL) and phytase (PHY), either alone or in combination, and days on trial on coefficient of total-tract digestibility (CTTAD) and performance. The diets used were: (i) positive control (PC); (ii) negative control with reduced energy and mineral content (NC); (iii) NC with added XYL (NCX); (iv) NC with added PHY (NCP); and (v) NC with added XYL plus PHY (NCXP). The performance response and CTTAD of dietary components were measured 3 and 7 weeks after commencement of feeding, with the experiment finishing when pigs reached approximately 65 kg live weight.Pigs fed the NC diet decreased average daily gain (ADG) by 13% (P<0.01) and increased feed conversion ratio (FCR) by 11% (P<0.01) compared to pigs fed the PC diet. Addition of PHY in the NC diet increased ADG by 9% (P<0.05) and decreased FCR by 5% (P=0.065), whilst addition of XYL in the NC diet had no effect on the performance indices. Combined addition of XYL and PHY in the NC diet did not improve performance of pigs for the first 21 days but improved FCR by 8% (P=0.008) during the days 22–49. Digestibility measurements showed that combined use of XYL and PHY in the NC diet improved CTTAD of dry matter (DM, P<0.05), gross energy (GE, P<0.05) and crude protein (CP, P<0.01) only during the days 22–49. Independent supplementation of PHY in the NC diet tended to improve CTTAD of GE (P=0.09) only during the days 22–49. In contrast, supplementation of PHY immediately improved CTTAD of P and maintained it to similar levels at 49 days. Results suggested that supplementation of PHY plus XYL in combination in the NC diet improved FCR and CTTAD of DM, GE, CP and P but the beneficial effects other than CTTAD of P were derived mainly during days 22–49.