A feeding trial was conducted in Fish Research Laboratory in Kafr EI-Sheikh,
Faculty of Agriculture, Tanta University to study the effect of supplementing betafin as
a pure form of betaine in the diet of monosex Nile tilapia (Oreochromis niloticus)
fingerlings on their growth performance and efficiency of feed and protein utilization. A
set of 195 fingerlings monosex Nile tilapia with about 22 g average initial weight were
taken from the stock of a private hatchary in Kafr EI-Sheikh Governorate. The fish
were transported into glass aquaria in Kafr EI-Sheikh, Faculty of Agriculture and
adapted for one month before the beginning of the experiment. The fish were divided
into 15 similar groups and randomly distributed into 15 glass aquaria (80 x 35 x 40
ern) with 13 fish in each. A basal diet containing about 29 % crude protein was
formulated from the commercial ingredients (Fish meal, soybean meal, yellow corn,
wheat bran, cellulose and vitamin and mineral mixture). Betafin was added to the
basal diet at 0, 2, 4, 6 and 8 g/Kg deit or 0, 0.2,0.4 , 0.6 and 0.8 % of the total diet.
The basal diet without betafin was considered as a control diet. The experimental
diets were fed to fish groups at 3 % of their total biomass for 56 days. The results
showed that growth parameters including body weight gain (BWG), average daily gain
(AOG) and specific growth rate (SGR) were the highest in the groups fed diet
containing 8 g betafin/kg, while the lowest values were obtained in the groups of the
control diet . All betafin supplemented diets significantly improved BWG, AOG, SGR,
FeR, PER and PPV as compared with the unsupplemented diet (control). Fish body
composition was not affected by the supplementation of betafin in the diet. It is recommended to supplement the diet of Nile tilapia with betafin at 4 g/kg