he main objective of this study was to evaluate the effect of partial and total replacement of fish meal protein by sesame seed meal (SSM) protein in commercial diets on growth performance, feed utilization and body
composition of juvenile mono sex Nile tilapia, Oreochromis niloticus (L.). Fish of an average initial weight of 0.60 ± 0.01 g were stocked in 15 glass aquaria (80 l each) at a rate of 15 fish per aquarium. Fish meal protein (18% of the diet) was
used as the sole source of animal protein in the control diet. Percent replacements of fish meal by sesame seed meal on the basis of crude protein were as follows: 0 % (control diet A), 25 % (diet B), 50 % (diet C), 75 % (diet
D) and 100 % (diet E). All tested diets were almost isonitrogenous and fed at a rate of 4 % of fish body weight, and then gradually reduced to 3 % of the total fish biomass daily, for a period of 16 weeks. The results of this study revealed
that, fish fedon diet A (100 % FM) had the highest average body weight, specific growth rate (SGR), weight gain %, feed conversion ratio (FCR), and protein efficiency ratio (PER), but the lowest was obtained with fish fed diet E (100 %
SSM). The same parameters of fish fed on diets B (25 % SSM) and diet C (50 % SSM) were not significantly different (P > 0.01) from those of fish fed on the control diet A. Proximate composition of the whole body moisture and ash
contents were not significantly affected (P>0.05) by the dietary treatments.Whole body protein contents for fish fed on diets B, C and D were superior to the control diet. Incorporation of sesame seed meal in the fish diets increased
significantly whole body fat content. Incorporation of sesame seed meal in the diets significantly increased apparent digestibility coefficients of crude protein, crude fat and energy. Therefore, these results suggest that up to 50 % of fish
meal protein can be replaced by sesame seed protein in mono sex Nile tilapia diets without any adverse effect on growth performance and feed utilization,body composition and digestibility.