Animal Nutrition and Feed Technology

Nile tilapia (Oreochromis niloticus) is important as a newly introduced species to inland aquaculture industry of Iran. Feed is the most important economic factor, and protein, the most expensive ingradient represents more than 50% of expenses was investigated. All male Nile tilapia (180) with initial weight 13.85±1.01 g divided randomly in 12 tanks (150 L, 3 L/min water flow) and fed with 4 diets (15, 22, 29 and 36% crude protein) during 8 weeks. Survival did not affect by increasing protein level. Growth, food and protein performance indices improved significantly (P<0.01) up to CP 29. The most economical diet for getting convince growth, food and protein performance was 29% crude protein. Mathematical model (polynomiyal) between PCE and protein level showed the maximum protein efficiency appeared in 35.3% crude protein.