Two feeding trials were conducted in the present study with red tilapia. In the two trials nine experimental diets of 25, 30 and 35% protein contents and within each level, three levels of metabolizable energy (ME) 2400, 2800 and 3200 kcal ME/kg representing nine P/E ratios ranged between 77.9 to 141.7 mg prot./kcal were tested. In the first trial red tilapia fry (0.70 – 0.82 g) fed the experimental diets at a daily rate of 20% (during the 1st month) and then decreased to 10%(2nd month) of the total biomass. In the second experiment, red tilapia fingerlings (9.06 – 9.59 g) fed the experimental diets at a daily rate of 10% (during the 1st month) and then gradually decreased to 7%(2nd month) and finally to 4% (during the last two months) of the total biomass. The obtained results indicated that: Increasing dietary protein or energy contents in the diets of red tilapia fry and fingerlings increased all growth parameters (body weight, body length, weight gain and specific growth rate). At all nine P/E ratios the best growth parameters (body weight, body length, weight gain and specific growth rate) were obtained with the diet containing 35% crude protein and 3200 kcal ME/k g (P/E ratio of 110.3 mg protein/kcal) but the diet contained 25% crude protein and 2400 kcal ME/kg (P/E ratio of 105.6) had the lowest growth parameters. It is also found that increasing protein or energy levels in red tilapia fry and fingerlings diets significantly improved feed intake (FI) and feed conversion ratio (FCR). Also, At all nine P/E ratios the best feed efficiency parameters (feed conversion ratio and protein efficiency ratio) were obtained with the diet containing 35% crude protein and 3200 kcal ME/k g (P/E ratio of 110.3 mg protein/kcal) but the diet contained 25%. Crude protein and 3200 kcal ME/100 g (P/E ratio of 77.9) had the worst FCR. Increasing dietary protein and energy content in red tilapia fry and fingerlings significantly decreased protein and increased fat contents of red tilapia bodies. Generally, based on the present results, the experimental diet containing 35% crude protein and 3200 kcal ME/kg (P/E ratio of 110.3 mg protein/kcal) considered the most suitable diet for red tilapia fry and fingerlings reared in tanks. |
