Growth Rate, Feed Conversion, and Body Composition of Catla catla, Labeo rohita, and Cirrhinus mrigala Fry Fed Diets of Various Carbohydrate‐to‐Lipid Ratios

Abstract

Abstract.Effects of dietary carbohydrate‐to‐lipid (CHO : L) ratios on the growth rate, conversion efficiencies, and body composition were studied in the Indian major carp fry Catla catla, Labeo rohita, and Cirrhinus mrigala. Six isonitrogenous (40% crude protein) and isocaloric (3.46 kcal metabolizable energy/g) semi‐purified diets, with CHO: L ratios of 0.02, 0.60, 1.54, 3.38, 8.93, and 43.00 were fed to triplicate groups of fish in 70‐L flow‐through (1.5–2.0 L/min) indoor circular troughs. Fish were fed to apparent satiation (about 10% body weight), 6 d/wk, twice daily at 0800 and 1600 h for 6 wk. Fish growth rates differed significantly (P < 0.05) with CHO: L ratio in the diets. Maximum weight gain (%) and specific growth rate (SGR %) were observed in C. catla and L. rohita fed a diet with 36% carbohydrate and 4% lipid, corresponding to a CHO: L ratio of 8.93. In C. mrigala, highest weight gain (%) and SGR (%) were noted in fish fed 27% carbohydrate and 8% lipid, corresponding to a CHO: L ratio of 3.38. In all the species, fish fed either diet with the lowest (0.02) or the highest (43.00) CHO: L ratio tended to have significantly lower (P < 0.05) growth and conversion efficiencies. Percentage of dry matter and whole‐body lipid of fish significantly (P < 0.05) increased as CHO: L ratio decreased. However, whole‐body crude protein content of fish significantly (P < 0.05) increased as CHO : L ratio increased. The results of this study indicate that the Indian major carp fry efficiently utilize carbohydrate for energy, and excess dietary lipid resulted in increased lipid accumulation in the body.