Hua, K., and Bureau, D.P. (2006) Modelling digestible phosphorus content of salmonid fish feeds. Aquaculture, 254 (1-4). pp. 455-465.

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Abstract

Accurate estimation of digestible phosphorus (P) content of fish feeds is essential to formulating feeds that meet nutritional requirements of fish but minimize P waste output from fish culture operations. Phosphorus is a component of different chemical compounds in feeds. Differences in chemical characteristics of these compounds may result in different P digestion dynamics. A model to estimate digestible P content of salmonid fish feed based on levels of different P types was constructed by integrating data from 22 studies. Phosphorus types present in feed ingredients were classified into broad chemical categories: bone-P, phytate-P, organic P, Ca monobasic/Na/K Pi supplement, and Ca dibasic Pi supplement. The relationship between digestible P content of feeds and various P chemical compound contents was modelled through a multiple regression approach.

Multiple regression analysis yielded the following model: digestible P=0.68 bone-P+0 phytate-P+0.84 organic P+0.89 Ca monobasic/Na/K Pi supplement+0.64 Ca dibasic Pi supplement+0.51 phytase/phytate-0.02 (phytase/phytate)(2)-0.03 (bonep)(2)-0.14 bone-P*CamonobasicNa/K Pi supplement (P < 0.0001, R-2 = 0.96). The results suggest that the digestibility of different P types differ significantly and the digestibility of bone-P is not additive. A subsequent digestibility trial validated the model and suggested that the model accurately predicted digestible P content of diets formulated with a wide variety of ingredients commonly used in fish feeds.

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