Abstract
Olive waste was evaluated as a substitute ingredient for wheat bran in tilapia (Oreochromis niloticus) diets. Five experimental diets viz., 0 (control), 25, 50, 75 and 100% olive waste (OW) replaced with wheat bran were prepared and randomly allotted to triplicate groups with 10 fish in each group. Fish were reared in glass aquaria at a water temperature of 29 1 C with a dark/light cycle of 12 h. Fish were fed at 3% of body weight twice daily for a period of 70 days. The increasing level of olive waste in tilapia diets significantly (P < 0.05) reduced the growth performance and efficiency of feed utilization in fish. However, the replacement of wheat bran with 25% OW did not affect (P > 0.05) the feed intake (FI) weight gain (WG), specific growth rate (SGR), condition factor (k), feed conversion ratio (FCR) and protein efficiency ratio (PER) in fish as compared to fish fed control (100% wheat bran). The replacement of wheat bran with 50, 75 and 100% OW significantly (P < 0.05) reduced the growth performance and efficiency of feed utilization in Nile tilapia in terms of feed intake, body weight gain, SGR, condition factor, FCR and PER. The substitution of olive waste with wheat bran at all levels did not affect (P > 0.05) the moisture and crude protein contents of fish muscles. The fish fed diet containing 100% OW, however, showed significantly higher muscle lipid contents as compared to others. An irregular pattern was observed in the ash content of fish muscles fed various experimental diets. In conclusion, locally produced olive waste in Saudi Arabia can be used as a substitute ingredient for wheat bran only up to 25% level in tilapia diets without compromising their growth performance and efficiency of feed utilization. (C) 2011 Friends Science Publishers