Growth Performance of Nile Tilapia (<i>Oreochromis niloticus</i>) Fed Processed Soybean Meal Based Diets Supplemented With Phytase

Abstract

An 8-week feed trial was conducted in glass tanks (60×30×30cm) to assess the performance of fingerlings Nile Tilapia ( Oreochromis niloticus ) fed diets containing soybean meals processed by toasting and incubation methods. Six diets were formulated at 30% crude protein content with 0 (control), 2,000 units, 4,000 units, 6,000 units, 8,000 units and 10,000 units phytase/kg diet making diet/treatments. Each treatment was replicated twice, each replicate contained 15 fish (6.23 ± 0.1g). Fish were fed twice daily at 5% of their body weight. Mean Weight Gain (MWG), Specific Growth Rate (SGR), Feed Conversion Ratio (FCR) and Protein Efficiency Ratio (PER) were measured. Temperature, Dissolved oxygen and pH were determined using standard methods. Data were analyzed using descriptive statistics and ANOVA at p= 0.05. Results showed that fish fed diet 5 (8,000 units phytase/kg diet) had the best growth and nutrient utilization indices while fish fed the control diet (0 unit phytase/kg diet) had the poorest. The SGR, FCR and PER of the group of fish fed diets with 0, 2,000, 4,000, 6,000 and 10,000 units phytase/kg diet were not significantly difference (p > 0.05), while the SGR, FCR and PER of fishes fed diet with 8,000 units phytase/kg diet were significantly (p < 0.05) better than those of the fishes fed other diets. The values of temperature, dissolved oxygen and pH were closely related and were within the range for fish culture in the tropics. The results suggest that phytase inclusion in the diet of O. niloticus could be a potential and promising dietary supplementation that would positively influence growth and water quality of O. niloticus in aquaculture.