Effect of phytase alone or with xylanase on performance and tibia mineralization and phytate destruction in diets different in dietary undetermined anion levels
Ross 308 broilers were used to study the influence of supplementation of phytase alone or plus xylanase on performance, phytate degradation, bone mineralization, cecal volatile fatty acids (VFA), and digesta pH in diets marginally divergent in dietary undetermined anions (dUA). On d 1, 336 male birds were allocated to 7 treatments (6 replicates, 8 birds each). Diets were adequate in nutrients (positive control, PC) or reduced either by 1.5 g/kg available P, 1.6 g/kg Ca; 0.3g/kg Na and 4.2 g/kg crude protein (negative control 1, NC1) or by 1.9 g/kg available P, 2.1 g/kg Ca, 0.5 g/kg Na and 5.5 g/kg protein (negative control 2, NC2). In the remaining treatments NC1 and NC2 diets were supplemented with phytase (1,500 FTU/kg) alone or plus xylanase (16,000 BXU/kg). Birds and feeds were weighed on d 0 and 21. After slaughter (d 21), left tibia bones and digesta samples from different parts in the intestine were collected. Data were analyzed by ANOVA and means were separated using PDIFF and LINES options of SAS. Differences in body weight and feed intake between treatments were not significant but there was poorer FCR (P < 0.01) in NC1 and NC2 compared with PC birds. Phytase with xylanase improved FCR (P < 0.05) to the level of the PC birds. Phytase alone improved FCR (P < 0.05) in the NC2 diet. Differences in phytate degradation at the terminal ileum were found between treatments. More pronounced mineral reduction (NC2) improved phytate destruction but not to the level achieved by phytase alone or combined with xylanase. Tibia ash content was lower (P < 0.01) in NC1 and NC2 compared with PC birds and was improved (P < 0.01) by phytase alone or combined with xylanase. Treatment differences in bone ash were more distinct in the diaphysis compared with the epiphysis. The treatments had no effect on the digesta pH or on ceca VFA. It is concluded that the reduction of P, Ca and Na and protein reduced FCR and tibia mineralization and the negative effects were reversed by supplementation of phytase plus xylanase.
Other Titles/Title of Conference
Poultry Science Association Annual Meeting, Corpus Christi, USA