Growth, reproductive performance, muscle and egg composition in grass carp, Ctenopharyngodon idella (Valenciennes), fed hydrilla or formulated diets with varying protein levels
2004
Khan, M.A. | Jafri, A.K. | Chadha, N.K.
Growth, reproductive performance, muscle and egg composition were investigated in grass carp, Ctenopharyngodon idella (Valenciennnes), fed hydrilla or formulated diets with varying protein levels. Five experimental diets, with varying levels (20%, 25%, 30%, 35% and 40%) of crude protein (CP), were used. One of the fish groups was fed hydrilla. Fish (44.1±0.3 cm; 913±9 g) were stocked (20 tank-1) in outdoor concrete tanks (20 x10 x 1.5 m) in duplicate, and fed to satiation, twice daily, at 09:00 and 17:00 hours for the experimental duration of 360 days. High (P<0.05) weight gain was recorded in fish fed 30% and 35% CP diets. However, values for gonadosomatic index (GSI), egg diameter, relative fecundity (eggs kg-1 body weight), fertilizability and hatchability (%) were comparable (P>0.05) in fish at > or = 25% of dietary protein intake. Hydrilla-fed fish exhibited lower (P<0.05) values for the measured parameters. Crude protein content in muscle increased with dietary protein level. Highest (P<0.05) muscle protein was obtained in fish fed 35% CP diet. Muscle fat was comparable (P>0.05) among fish receiving formulated diets. Ash content was not significantly (P>0.05) different among fish of different dietary groups. Moisture content in fish fed formulated diets, with the exception of 20% CP diet, did not vary significantly (P>0.05). Eggs of fish fed formulated diets contained higher CP and fat contents than those of hydrilla-fed fish. High (P<0.05) moisture content was noted in the eggs of hydrilla-fed fish. Ctenopharyngodon idella fed formulated diet, with a minimum of 25% CP, showed better reproductive performance than those fed hydrilla.
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