Evaluation of lipid and lipid levels in the diet of pearlspot, (Etroplus surantesis)(Bloch).

Abstract

Seven different oils namely, coconut oil, cod liver oil, gingely (sesame seed) oil, groundnut oil, sunflower oil, soybean oil and sardine oil were evaluated in the diet of pearlspot (Etroplus suratensis). These oils were individually incorporated at 7% level in an iso-nitrogenous diet consisting of a protein base, other ingredients and binder. In the second experiment, a mixture of coconut oil and sardine oil (which gave the best results in the first experiment) in the ratio of 1 : 1 was prepared to study the effect of dietary lipid levels on growth of pearlspot. Seven more iso-nitrogenous diets were formulated with the above mixed lipid supplementation of 0 to 15%.The results of the 35-day feeding trial with test diets having different lipid sources showed that the fish (initial weight 15-20 g) fed with diet containing coconut oil led to significantly (P<0.05) higher weight gain of 23.91±1.92 g followed by the diets with sardine oil (19.2±0.89 g), cod liver oil (19.15±1.24 g), gingely oil (16.52±0.66 g) and the control diet led to a weight gain of 19.24±0.59 g. The specific growth rate also followed similar trend. The weight gain of fish fed with diets having groundnut oil, sunflower oil and soybean oil is marginally less than that of the control diet indicating that dietary addition of these oils had no beneficial effect on growth. The diet with coconut oil led to significantly (P<0.05) lower FGR (1.60) followed by that containing cod liver oil (1.96) and sardine oil (2.0). The growth of fish increased, feed gain ratio (FGR) and protein efficiency ratio (PER) improved with increase in lipid supplementation in the diet up to 5%. The diet with a total lipid content of 8.6%(with 5% supplementation) gave significantly (P<0.05) higher weight gain (18.24±0.84 g), specific growth rate (1.0590) and lowest FGR (1.6). This diet also gave significantly (p<05) better PER (1.94). Further increase in the lipid supplementation in diet had negative effect on growth, SGR, FGR and PER. The results obtained in this study can be utilized for formulating practical feeds using appropriate lipid sources for feeding pearlpsot for its aquaculture. This study also leads to further investigations on more specific dietary fatty acid requirements of Etroplus suratensis.