Clinical changes observed in Clarias gariepinus (Burchell 1822) fed varying levels of ascorbic acid supplementation

Abstract

This study was undertaken to observe the clinical changes associated with the dietary ascorbic acid supplementation in the diet of African catfish, Clarias gariepinus, using the presence or absence of scorbutic (ascorbic acid deficiency) symptoms as indices. C. gariepinus fingerlings weighing 6.02±0.4 g were randomly distributed into glass tanks of 60 × 45 × 45 cm3 dimension at ten fish per tank in a triplicate treatment. Five isonitrogenous and isocalorific diets containing 40% crude protein was formulated. Ascorbic acid (AA) was supplemented in the diets as ascorbyl-2-polyphosphate (a mixture of phosphate esters of ascorbate). Each treatment had varying levels of ascorbic acid (AA) supplementation, at 0 (Control) 50, 100, 150 and 200 mg AA/kg, in Treatment 1, 2, 3, 4 and 5 respectively. Fish were fed practical diets twice daily at 900 and 1600 h GMT. Weekly weighing of fish was done and the data collected were subjected to statistical analysis. At the end of week 4, fish fed scorbutic diets (diets without ascorbic acid supplementation) had significantly lower weight than fish fed AA supplemented diets (P<0.05). After week 6 fish fed scorbutic diet began to develop clinical symptoms including lordosis (lateral curvature), broken skull, pigmentation and scoliosis (vertical curvature). Radiographs confirmed defects in the vertebral columns of fish in this treatment. Highest mortality was recorded in this treatment as 30%, followed by treatment two fed 50 mg AA/kg which had 10% mortality, fish in this treatment also showed some clinical signs like eroded fins and pigmentation. In all parameters considered, treatment 4 fed 150 mg AA/kg gave the best AA supplementation that prevented growth reduction and clinical signs of AA deficiency in this study. Key words: Clinical, ascorbic acid, Clarias gariepinus, scorbutic, supplementation.