Determination of Optimum Dietary Carbohydrate Level of Long Whiskers Catfish, Mystus gulio Fry

The objective of the present study is to evaluate the optimum dietary carbohydrate level of M. gulio fry, which will form the basis for formulating the nutritionally adequate, cost-effective nursery diet. Five iso-proteinous (400 g kg-1 diet) and iso-lipidic (120 g kg-1 diet) semi-purified diets with  100, 150, 200, 250 and 300 g carbohydrate kg-1 diet were fed ad libitum to Mystus gulio fry (0.33 ± 0.004 g)  for 90 days in triplicates (10 fish/replicate). Fifteen fibre-reinforced plastic tanks (50 L) with flow-through system (water flow rate of 0.5 L min-1) were used for rearing the fish. At the end of the feeding period,  the diet containing 200 g kg-1 carbohydrate diet had significantly higher (P = .05) weight gain (8.39 g), Specific Growth Rate (SGR; 3.62 %/day), Protein Efficiency Ratio (PER; 1.52), Protein Productive Value (PPV; 24.08%), Lipid Productive Value (LPV; 27.13%), Energy Productive Value (EPV; 66.89%) and lower Food Conversion Ratio (FCR; 1.65) as compared to other diet fed groups. The fish fed with carbohydrate beyond 200 g kg-1 diet had significantly higher (P = .05) Hepatosomatic index (HIS) and Visecerosomatic index (VSI) than the lower carbohydrate fed groups. Second order polynomial regression analysis of weight gain, SGR, FCR, PER and PPV against the dietary carbohydrate had showed that the optimum dietary carbohydrate requirement of M. gulio fry is 197.8-207.3 g kg-1 diet.