A 8 week feeding trial was conducted on Nile tilapia, Oreochromis niloticus fingerlings with an average initial body weight of 15.30±0.32 g. Nine experimental diets of 20, 25 and 30% protein contents and within each level, three levels of metabolizable energy (ME) 300, 330 and 360 kcal ME/100 g representing nine P/E ratios ranged between 55.5 to 98.9 mg prot/kcal were tested. The obtained results indicated that:
- Increasing dietary protein content increased all growth parameters (body weight, weight gain, body length, condition factor and specific growth rate) but increasing dietary energy contents showed the opposite trend. At all nine P/E ratios the best growth parameters (body weight, body length, condition factor, weight gain and specific growth rate) were obtained with the diet containing 30% crude protein and 300 kcal ME/100 g (P/E ratio of 98.9 mg protein/kcal) but the diet contained 20% crude protein and 360 kcal ME/100 g (P/E ratio of 55.5) had the lowest one.
- It is also found that increasing protein level improved feed intake and feed conversion ratio but decreased protein efficiency ratio and dietary energy level had the opposite effect. Also, the diet contained P/E ratio of 98.9 mg protein/kcal improved feed intake and feed conversion ratio. Protein levels tested in the present study showed insignificant effect on most carcass characteristics. Although, energy level in the experimental diets had insignificant effect on carcass traits and proximate analysis of the experimental fish, it was found that, increasing dietary protein for tilapia decreased protein and fat contents in tilapia bodies.
- Generally, based on the present results the experimental diet contained P/E ratio of 98.9 considered the most suitable diet for Nile tilapia reared in tanks.
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