Effect of phytase supplementation on the growth, mineral composition and phosphorus digestibility of African catfish (<i>Clarias gariepinus</i>) juveniles

Abstract

This study investigates the effect of phytase supplemented diets on growth, bone mineralization and phosphorus digestibility of African catfish Clarias gariepinus. A 40 % crude protein diet was produced using fishmeal, soybean meal, lima bean meal, groundnut cake and yellow maize as ingredients. Diets E0, E1, E2 and E3 were supplemented with phytase (Natuphos microbial phytase, 5000 FTU/g; BASF) at 0, 1000, 2000 and 4000 FTUkg -1 feed respectively. The diets were fed to C. gariepinus (25.28 ± 0.03g) at 3 % body weight at two equal instalments daily. After 98 days of feeding, results indicated that mean weight gain (MWG) were significantly higher (p<0.05) in fish fed E1 (63.82 g), E2 (66.71 g) and E3 (64.98 g) than E0 (55.76 g). Feed consumed was marginally highest in E2 (110.91g) and least in E0 (103.83g). Phosphorus digestibility were significantly lower (p>0.05) in E0, with phytase resulting in over 28 % improvement. Calcium, phosphorus and zinc were highest in the carcass of E3 (30.23 mg/g, 31.96 mg/g and 52.78 µg/g respectively) and least in E0 (18.81 mg/g, 24.83mg/g and 35.55 µg/g respectively). Results also indicate significant increase (p<0.05) in bone minerals of fish fed diets E1, E2 and E3. Faecal phosphorus decreased with increase in phytase supplement from 15.98 mg/g in E0 to 11.01 mg/g in E3. Value of fish produced and profit index were significantly higher (p<0.05) in fish fed diets supplemented with phytase.

Keywords: Clarias gariepinus, Growth, Digestibility, Calcium, Phosphorus, Zinc