Dietary available phosphorus requirement of juvenile walking catfish,<i>Clarias leather</i>

Abstract

A feeding trial was conducted to evaluate the optimum requirement of dietary available phosphorus (AP) for juvenile walking catfish, Clarias leather. Six practical diets were formulated to contain graded levels (2.2, 3.9, 5.5, 7.1, 8.8 and 10.4 g kg−1) of AP from dietary ingredients and monocalcium phosphate. Each diet was randomly fed to triplicate groups of fish with initial mean weight of 7.94 ± 0.08 g in floating cages (1.5 × 1.5 × 2.0 m) suspended in an earthen pond, and each cage was stocked initially with 60 fish. Fish were fed thrice daily (07:30, 13:00 and 17:30) to apparent satiation for 10 weeks. Both specific growth rate (SGR) and protein efficiency ratio significantly increased with increasing AP from 2.2 to 5.5 g kg−1 (P < 0.05) and then levelled off. Dietary AP levels significantly influenced whole-body protein, lipid and ash contents as well as condition factor and hepatosomatic index (P < 0.05). Whole-body and vertebrae phosphorus contents showed similar patterns as SGR in response to dietary AP content. Broken-line analyses based on SGR, phosphorus contents in the vertebrae and whole-body indicated the AP requirements were 5.8, 7.2 and 7.5 g kg−1, respectively.