Effect of dietary lipid levels on growth, nutrient digestibility and digestive enzyme activity of the peninsular carp Hypselobarbus pulchellus (Day, 1870)

Dietary lipid requirement of Hypselobarbus pulchellus was investigated through a feeding trial conducted for 90 days with five isonitrogenous diets formulated to contain lipid levels ranging from 2.5 to 12.5%. Fingerlings (initial weight 1.33±0.06 g and length 5.14±0.32 cm) were fed to apparent satiation twice daily. The final weight and length gain (%) decreased at 12.5% lipid incorporation level with no difference among other treatments. Food conversion and protein efficiency ratios of the experimental diets were the best with 2.5% diet and decreased significantly with 12.5% diet. Fish carcass crude protein values reduced and fat values increased at 10% lipid feeding. Crude protein digestibility was higher with diets 2.5, 5.0 and 7.5% compared to 10 and 12.5% lipid levels. Fat digestibility value was lowest under 2.5% lipid level and comparable among other treatments. Highest activity of gut protease, amylase and lipase was observed at 7.5% lipid level with the lowest activity of protease and amylase at 12.5% level and that of lipase at 2.5% level. The study indicated that the species has relatively low capacity to endure high-energy intakes. Nevertheless, considering the higher activity of digestive enzymes and digestibility of dry matter and crude protein, a dietary fat level ranging between 5 to 7.5% is recommended for the species. A second- order polynomial regression analysis indicated an optimum dietary lipid level of 6.6% in the feed for the species. Keywords: Dietary fat, Lipid requirement, Puntius pulchellus, Species diversification