EFFECTS OF COMBINED PHYTOGENIC COMPOUNDS ON GROWTH AND NUTRITIONAL PHYSIOLOGY OF NILE TILAPIA OREOCHROMIS NILOTICUS

Phytogenics, plant products that can be in form of ground herbal parts or essential oils extracted from plants, are among feed additives being evaluated in fish diets to enhance fish growth and feed efficiency. Phytogenic products contain various bioactive compounds at different concentrations, with those at higher concentrations primarily determining biological properties of phytogenics. In our previous research, phytogenic compounds limonene and thymol, major constituents of the plants citrus and thyme respectively, were found to have growth-promoting effects in Nile tilapia (Oreochromis niloticus). It is argued that combinations of some phytogenic compounds might have stronger growth-promoting effects than their individual compounds. Moreover, the mode of action of phytogenics in enhancing fish growth is not well understood especially with respect to nutritional physiology. This study was therefore carried out to investigate the effects of a dietary combination of limonene and thymol, compared with each compound individually, on the growth and nutritional physiology of Nile tilapia.