Abstract
AbstractGrowth, reproductive performance, muscle and eggcomposition were investigated in grass carp, Cteno-pharyngodon idella(Valenciennnes), fed hydrilla orformulated diets with varying protein levels. Fiveexperimental diets, with varying levels (20%, 25%,30%,35%and40%)ofcrudeprotein(CP),wereused.One of the ¢sh groups was fed hydrilla. Fish(44.1 10.3 cm; 913 9g) were stocked (20tank )inoutdoorconcretetanks(20 10 1.5m)induplic-ate, and fed to satiation, twice daily, at 09:00 and17:00 hours for the experimental duration of 360days.High(Po0.05)weightgainwasrecordedin¢shfed30%and35%CPdiets.However,valuesforgona-dosomatic index (GSI), eggdiameter, relative fecund-ity (eggskg 1 body weight), fertilizability andhatchability (%) were comparable (P40.05) in ¢shat 25% of dietary protein intake. Hydrilla-fed ¢shexhibited lower (Po0.05) values for the measuredparameters. Crude protein content in muscle in-creased with dietary protein level. Highest (Po0.05)muscle proteinwas obtained in ¢sh fed 35% CPdiet.Muscle fat was comparable (P40.05) among ¢sh re-ceiving formulated diets. Ash content was not signi-¢cantly (P40.05) diierent among ¢sh of diierentdietary groups. Moisture content in ¢sh fed formu-lated diets, with the exception of 20% CP diet, didnot vary signi¢cantly (P40.05). Eggs of ¢sh fed for-mulated diets contained higher CP and fat contentsthan those of hydrilla-fed ¢sh. High (Po0.05) mois-turecontentwasnotedintheeggsofhydrilla-fed¢sh.Ctenopharyngodon idellafed formulated diet, with aminimumof25%CP,showedbetterreproductiveper-formancethanthosefedhydrilla.Keywords: dietary protein, hydrilla, Ctenopharyn-godon idella, reproductive performance, proximatecomposition, eggsIntroductionGrass carp, Ctenopharyngodon idella (Valenciennes),feeds naturallyon avariety of macrophytes and hasbeenwidely used for biological control of aquatic ve-getation in various parts of the world (Cross 1969;Chaudhuri, Murty, Dey & Reddy 1976; Leslie Jr, VanDyke, Hestand III & Thompson1987; Jagdish, Rana A Rath, Gupta & Dasgupta1999). Studies on b roodstock nutrition are relatively
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