Effects of Dietary Protein Level on Growth Performance, Carcass Composition and Survival Rate of Fry Monosex Nile Tilapia, Oreochromis niloticus Reared under Re-circulating System

Fry monosex Nile tilapia ( Oreochromis niloticus ) were fed in five dietary protein levels (21%, 25%, 32% 37% and 45%) to investigate casual effects on growth performance, carcass composition and survival rate. Tests were carried out in 10 glass tank (50 x 25 x 40 cm) containers (50 L) of reticulating system maintained at 30 ± 1°C. At the beginning of tests, one hundred tilapia fry were randomly divided into five different groups with two replicates. Diets were fed to duplicate groups of ten fry with an initial weight of 1.25 ± 0.25 g/fish during 42 days. The results showed significant effects of dietary protein on growth performance of reared fish. Weight gain (WG) and Specific Growth Rate (SGR) increased significantly with increasing dietary protein levels between 32.38% and 37.63%. However, 45.5% of crude protein showed less important increase in growth parameters. The best Feed Conversion Rate FCR (1.26) was noticed in diet containing 37.63% of crude protein. Accordingly, higher survival rate (%) was recorded in fish fed on diets containing 32.38 and 37.63%. There was no significant difference in protein body content of tilapia fed on five diets as compared to the initial fish. Lipid body content increased significantly with high dietary protein levels from 21.88% to 45.50%. The carcass crude lipid was recorded as higher (9.4%) in the fry fed on diet containing 45.50% protein, followed by fish fed on diet having protein 21.88%. From results, diet containing 37.63% crude protein appears to be more suitable for monosex Nile tilapia growth, in related experience conditions. In this line, it is recommended to feed monosex tilapia fry.