Benjamin U.A.¹ , Emmanuel K.A.² , Bamidele O.O.²

1 Department of Fisheries, University of Port Harcourt, Nigeria
2 Department of Aquaculture and Fisheries Management, University of Ibadan, Nigeria
Author    Correspondence author
International Journal of Aquaculture, 2015, Vol. 5, No. 41   doi: 10.5376/ija.2015.05.0041
Received: 26 Oct., 2015    Accepted: 10 Dec., 2015    Published: 14 Feb., 2016

This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Akpoilih B.U., Ajani E.K. and Omitoyin B.O., 2015, Dietary Phytase Improves Growth and Water Quality Parameters for Juvenile Clarias gariepinus Fed Soyabean Meal-based Diets, International Journal of Aquaculture, 5(41): 1-20

The effect of phytase on growth, nutrient utilization of juvenile Clarias gariepinus fed soya bean using a 4x5 experimental design was investigated. 15.13% (S1), 34.16% (S2), 58.85% (S3) and 92.15% (S4) soyabean were formulated to substitute fish meal at 25 %, 50 %, 75 % and 100 %, respectively as basal controls with no phytase (P0). Another four diets were formulated with the same composition as the basal diet, but were supplemented with 250 FTU/g (P1), 500 FTU/g (P2), 750 FTU/g (P3) and 1000 FTU/g (P4), respectively. A fish meal diet, S0 (100%) and commercial diet (comm. diet), which served as controls, were included in the experiment to compare growth performance with experiment diet. A total of 1638 fish of average weight 11.55+ 0.20g were randomly allocated to experimental diets and fed at 3% body weight to replicate group of fish stocked at 26 fish per tank for 84 days. Growth performance was significant with phytase addition to diet (ANOVA, P<0.05). Mean weight gain declined with increasing substitution of fish meal by soya bean (Duncan, P<0.05), and irrespective of phytase levels (Tukey, P<0.05). However, significant improvement in weight gain of fish was observed with phytase addition to diets compared to diets without phytase (Tukey, P<0.05). Mean weight gain and feed conversion ratio (FCR) for fish fed S3P1 and S0P0 did not differ significantly (Duncan, P>0.05). Significant interaction for survival of fish showed a decline with increasing phytase, regardless of soya bean levels (Tukey, P<0.05). However, survival of fish fed fish meal diet was less than soya bean substitution up to 75%, regardless of phytase level (Turkey, P>0.05). Improvement in growth by phytase resulted in reduction of phytate (r= -0.231, P>0.05) and oxalate (r= -0.328, P<0.05) and improvement in water quality (Tukey, P<0.05) for oxygen (r= 0.262, P>0.05) and ammonia (r= -0.105, P>0.05). In conclusion, the study has demonstrated that phytase at low level of supplementation in soyabean diet of Clarias gariepinus can effectively utilize phosphorus from phytate, cut and manage pollution in aquaculture environments, and improve overall growth of fish compared to commercial diet.

Soyabean; Phytase; Growth; Water quality; Clarias gariepinus