Published online by Cambridge University Press: 01 September 2006
Optimal utilisation of limited phosphate resources in animal feeding requires detailed knowledge of both the requirement for available phosphorus (P), and the availability of P from relevant feed ingredients. In growing ducks, the P concentration of gained body weight and the inevitable P losses voided determine the requirement for available P. The concentration of available P needed in the diet then depends on the feed conversion ratio. Plant and mineral feedstuffs contribute to the available P content of the diet depending on their respective availability. This review summarises the literature on P nutrition in ducks with regard to factors affecting P requirement and considerations of P availability, including the use of microbial phytase. Most of the published data refer to the Pekin duck. The P content in body weight gain is 5.0–5.5 g/kg in young ducks, and it probably decreases with age. The ratio of Ca to P in body weight gain is about 1.8:1. Inevitable P losses are not yet quantified and can only be estimated to account for 1 g/kg of feed intake. Availability of P from plant-based diets without P supplements and phytase ranged between 28 and 49%. Availability of P from different mineral sources ranged between 77 and 100%. Microbial phytases were efficient in improving the availability of P from plant-based diets. A simple model is presented, which allows flexible calculations to be made of the necessary P concentrations in the diets for ducks. The most efficient tool for reducing the use of P sources is the frequent adjustment of the dietary P content during the growth period. Data from growth studies indicate that the suggestions made herein are sufficiently safe for application in Pekin duck feeding.