PHYTASE AS A FACTOR FOR IMPROVING GROWTH PERFORMANCE OF NILE TILAPIA (OREOCHROMIS NILOTICUS) FED ON PLANT-BASED DIETS

Hany I. El-Marakby

Department of
Fish Nutrition, Central Laboratory for Aquaculture Research, Agriculture Research Center, Egypt.

* Corresponding author email: [email protected]

Received 3/ 1/ 2012 Accepted 2/ 2/ 2012

Abstract

An experiment with average weight 1.5 g Nile tilapia, Oreochromis niloticus was conducted to evaluate the influence of phytase as a factor for improving growth performance of Nile tilapia fed on plant-based diets. The experimental period lasted 12 weeks; fish were randomly distributed into 15 glass aquaria in 5 treatments (3 replicates per treatment). The experiment was based on completely randomized design with five levels of dietary phytase supplementation 0, 250, 500, 750 or 1000 FTU/kg diet of phytase enzyme (1 g of phytase product content 2500 FTU). Phytase supplementation in fish diets significantly affects the wet live body weight after 8 and 12 weeks of the experimental period. Daily body gain and weight gain% gradually increased with increasing phytase level in fish diets. Fish group fed diets supplemented with 750 or 1000 FTU recorded higher body gain and daily weight gain than the other experimental groups. Also, fish group fed diets supplemented with 750 or 1000 FTU recorded the best feed conversion than the other experimental groups. The concentration of total protein, albumin and ALT in plasma increased with increasing phytase level in fish diets. Fish fed diets supplemented with 1000 FTU recorded higher concentrations of urea-N, creatinine and AST in plasma. Supplemented fish diets with phytase insignificantly affected the whole fish body compositions. Feed cost, return from body gain, and final margin increased gradually with increasing the level of phytase in fish diets. Fish fed diets supplemented with phytase 1000 FTU recorded the higher feed cost, return from body gain and final margin than the other groups. These results suggest that the supplementation of phytase (750 – 1000 FTU) in plant-based diets can significantly improve growth performance and feed utilization in Nile tilapia, O. niloticus fingerlings.

Keywords: Phytase, plant-based diet, growth rate, feed conversion, blood chemistry, body composition, profit analysis.