Optimum inclusion level of cotton seed meal as a source of protein in the diets of Nile tilapia, Oreochromis niloticus diet.

The present study was designed to investigate the effect of incorporation of cotton seed meal CSM in the diets of Nile tilapia Oreochromis niloticus. A set of 108 fish of O. niloticus L. mono-sex male fingerlings with average initial weight of 11.60 ±0.72 g was used in this trail. Twelve fish were randomly stocked into each aquarium with three replications for each treatment and fed the experimental diet (295 g kg^-1 crude protein) and isocaloric (18.76 MJ kg^-1 gross energy). The first diet CSM1 which contained (fish meal : cotton seed meal 2:1), the second CSM2  which contained (fish meal : cotton seed meal 2:2) and the third CSM3 which contained (fish meal : cotton seed meal 1:2). Results of the present experiment indicated that, inclusion of cotton seed meal CSM had slightly significant effect on final body weight BW between groups CSM1(FM: CSM; 2:1) and CSM2 (FM:CSM; 2:2),  but had no significantly effect on final BW between groups CSM1(FM: CSM; 2:1) and CSM2 (FM:CSM; 2:2). Weight gain (WG) and specific growth rate (SGR) were significantly higher in fish fed diet containing (FM: CSM 2:1) ratio, but no significant differences in WG, SGR and survival rate (SR) values of groups received the ratios of FM: CSM (2:2 and 1:2). The best feed conversion ratio (FCR), and protein productive value (PPV) were obtained by fish fed containing (FM: CSM= 2:1) followed by (FM: CSM= 2:1). There were no significant differences in protein efficiency ratio (PER). The highest apparent digestibility dry matter (DM) was obtained from fish fed diet containing (FM: CSM= 2:1) followed by (FM: CSM= 2:1), with significant (P>0.005) differences between FM: CSM = 2:1 and 2:2 ratio. The opposite trend was observed in apparent digestibility of protein. Meanwhile, there was no significant differences in apparent digestibility of lipid and energy.