A Simple Method for Determination of Available Phosphorus Content in Fish Diet

Abstract

The available phosphorus (P) contents in fish meal diets with or without supplemental P were determined by the indirect method in common carp and rainbow trout, which have different digestive systems. These values were compared with the amount of P fractionated with deionized water (Fr. I), 80 % acetic acid (Fr. II), and 0.25 m hydrochloric acid (Fr. 111), in order to simplify estimation of available P content in a fish feed. The determined available P contents in the fish meal diets for carp appeared to coincide with the amount of P extracted by deionized water (Fr. I). On the other hand, the available P contents in rainbow trout diets without supplemental P were found to be similar to the sum of P in Frs. I, II, and III, but those in the diets with supplemental P appeared to be equivalent to the amount of P in Fr. I. The results obtained in this study suggest that the value of P extracted with deionized water can be used for available P contents in carp feeds regardless of the kind of fish meal or supplementation of P. In the case of rainbow trout, P extracted with deionized water also can be used as an available P for the diets containing sufficient soluble P, but the summation of P in Frs. I, II, and III may be necessary for the estimation in feeds without supplementation of soluble P. © 1992, The Japanese Society of Fisheries Science. All rights reserved.