Dose-response relationship between a supplemented microbial phytase and utilisation of phosphorus from a maize/soybean meal-based diet in pekin ducks

Wendt, P.; Timmler, R.; Rodehutscord, M.

Growing male pekin ducks were fed a low-P diet mainly based on maize and soybean meal without an inorganic P source (3.2 g P and 5.5 g Ca per kg). Phytase from Aspergillus niger was supplemented at one out of the following levels (U/kg): 0, 150, 300, 450, 600, 900, 1200, and 1500. Each pelleted diet was fed at a level of 90 g/d to 7 ducks that were individually penned in balance crates. Intake and excretion were quantified over a period of 5 days between day 15 and 20 of age. P utilisation depending on phytase supplementation was subjected to non-linear regression analysis. As expected for such short-term balance studies, body weight gain and feed conversion ratio were not significantly affected by supplemented phytase. Utilisation of phosphorus from the unsupplemented basal diet was 28%. P utilisation followed typical saturation kinetics with increasing phytase supplementation and approached an asymptotic value of 63%. Cumulative efficiency of phytase, calculated as the amount of P released per 100 U was 0.12 g at low level of supplementation and went down to 0.06 g at the highest level under investigation. Replacement values for inorganic P can be calculated accordingly when the availability of P from different sources is considered. Utilisation of Ca was significantly increased by phytase supplementation as well.