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981
Effect of increasing Buttiauxella phytase dose to 2,000 FTU/kg on phytate degradation and ileal AA digestibility in weaned pigs
This study determined the effect of increasing Buttiauxella phytase dose on phytate degradation and ileal AA digestibility in weaned pigs. Six treatments were tested including a nutritionally adequate positive control (PC); a negative control (NC) with reduction of 0.1% Ca, 0.14% digestible P and 35 kcal/kg ME vs PC; NC supplemented with a Buttiauxella sp. phytase at 250, 500, 1,000 or 2,000 phytase units (FTU)/kg feed. One FTU was defined as the amount of enzyme required to release 1 µmol of iP per minute from sodium phytate at pH 5.5 at 37°C. Male pigs (Topigs x Pietrian, barrows, 20kg BW) were randomly allocated in metabolism crates (1 pig per crate) in 2 runs, 24 pigs in each run with a total of 8 replicates per treatment. Pelleted diets based on mixed grain (wheat, corn and barley) were fed for 9 d with 3 d adaptation, 5 d collection of feces and urine (for measuring apparent total tract digestibility, ATTD) and 1 d to collect ileal digesta (for measuring apparent ileal digestibility, AID, TiO2 as marker). The diets were supplied at 2.5 times energy requirement for maintenance in 2 equal meals per day, water was freely available. Treatment means were compared using Tukey’s HSD, linear or non-linear responses were determined using JMP 11 (SAS). Phytase at 2,000 FTU/kg showed greater (P < 0.05) nutrient digestibility vs NC or PC for most of the parameters. Increasing phytase dose from 0 (NC) to 2,000 FTU/kg linearly improved (P < 0.05) ATTD of P, retainable P, Ca, DM, N, ME as well as AID of P, N, Lys, Met, Cys, Thr, Val, Ile, Leu and mean essential AA. While AID of Ca and Trp increased in a non-linear manner. AID of phytate was 36, 39, 54, 67, 76 and 83%, respectively, for PC, NC, phytase at 250, 500, 1,000 and 2,000 FTU/kg feed (P < 0.05). The AID of phytate was linearly correlated with mean AID of AA (P < 0.05). In conclusion, increasing Buttiauxella phytase dose increased the level of phytate degradation, resulting in improved digestibility of AA and other nutrients. This demonstrated that increasing Buttiauxella phytase dose to 2,000 FTU/kg can lead to both phosphoric and extra-phosphoric effects.
Keywords: pigs, phytate degradation, AA digestibility