Effect of increasing Buttiauxella phytase dose on nutrient digestibility and performance in weaned piglets fed corn or wheat based diets

Two experiments were carried out to determine the effect of increasing phytase levels on apparent total tract digestibility (ATTD) of nutrients, P and Ca retention and growth performance in weaned piglets fed corn or wheat based diets. Five treatments were tested including a positive control (PC) meeting piglet nutrient requirements; a negative control (NC) formulated with a reduction in digestible P (-1.4 g/kg and -1.5 g/kg in Exp. 1 and 2 respectively) and Ca (-1.5 g/kg in both studies); and NC supplemented with a Buttiauxella phytase at 500, 1000 or 2000 phytase units (FTU)/kg feed. One FTU is defined as the amount of enzyme required to release 1 mu mol of iP (inorganic phosphorus) per minute from sodium phytate at pH 5.5 at 37 degrees C. A complete randomized design was used in both studies, with individual piglets housed in metabolic crates as the experimental unit. There were 2 runs in Exp. 1 and 4 runs in Exp. 2. Each treatment consisted of 8 replicates (1 piglet/replicate) in Exp. 1 and 12 replicates in Exp. 2. Diets based on wheat and soybean meal in Exp. 1 and corn and soybean meal in Exp. 2 were fed in pelleted form; feed and water were supplied ad libitum to the piglets (mean initial BW of 11 +/- 1.5 kg) during the 14 day period. Urine and feces production were collected from each crate during d 10 to14. The ATTD of P, Ca, DM, N and energy, and retention of P and Ca were measured using TiO2 as an indirect marker. In both Exp, increasing phytase dose from 0 (NC) to 2000 FTU/kg linearly increased (P < 0.05) ADG and G:F. Phytate at 2000 FTU/kg improved ADG and G:F compared to NC. A linear response was seen for ATTD of P, Ca and GE (P < 0.05) in Exp. 1, and for ATTD P and Ca in Exp. 2, with increasing phytase dose. Also there was a tendency for increasing phytase dose to result in a linear increase (P <= 0.10) in ATTD of DM in Exp.1, and ATTD of DM and N in Exp. 2. Increasing phytase dose linearly reduced P and Ca excretion and increased the retention of these nutrients in both experiments. The results showed that increasing Buttiauxella phytase dose up to 2000 FTU/kg may provide environmental and production benefits in weaned piglets fed either wheat or corn based diets.