Effect of dietary fishmeal replacement in the formulated food by heat processed soybean meal on growth, survival and crude protein level of fingerling
M.D.M.D.W.M.M.K.YATAWARA* AND M. HETTIARACHCHI
A feeding trial was conducted to evaluate the effect of dietary fishmeal replacement in the formulated food by heat processed soybean meal on growth, survival and crude protein level of fingerlings of Genetically Improved Farm Tilapia (GIFT). Six experimental diets were formulated to be isonitrogenous approximately. The diet 1 (control diet) contained 100% fishmeal and 0% soybean meal. Fishmeal was partially replaced by 10%, 25%, 30%, 40% and 50% of heat-treated soybean meal in the diets 2 to 6. Early GIFT fingerlings (body weight 1.92 ± 0.10 g) were reared in 164 L indoor fiberglass tanks and 3 replicates were arranged for each experimental diet. Each tank was provided with continuous mild aeration. Feed ration was 10% of total fish biomass over the first 30 days which was divided and offered at 09:00 h, 12:00 h and 16:00 h daily and the amount was reduced up to 8% of total fish biomass for the next 30 days. Results showed that percentage weight gain recorded in fish fed with the experimental diets 4, 5 and 6 (where fish meal was replaced by 30%, 40% and 50% soybean meal respectively) were not significantly different from that of fish fed with the control diet (P<0.05). There was no significant difference in specific growth rate of fish fed with the control diet and any of the experimental diets (P<0.05). Survival of the fish fed with the control diet and the fish that received the diet 5 was 100% at the end of 60 days study period. The lowest feed conversion ratios were recorded for the control diet (1.44) and for the experimental diet 5 (1.49). The fish fed with the diet 5 had the highest percentage of crude protein (59.35%), which was significantly higher (P<0.05) than that of the fish fed with diet 1 (control diet), 2 and 4. Cost of producing 1 kg of feed also was considerably low for the diet 5 compared to the control diet. The results show that 40% of fishmeal in a formulated diet for early fingerlings could be replaced by heat processed soybean meal with no adverse effects on growth, survival, FCR and crude protein level of young GIF tilapia at the end of 60 days of experimental period.