Optimization of dietary protein requirement for pond-reared mahseer Tor putitora Hamilton (Cypriniformes: Cyprinidae)

Abstract

AbstractAfeedingtrialwasconductedtostudytheeiectofsixiso-energetic diets containing 25, 30, 35, 40, 45 and50% crude protein (CP) ongrowth, survival and feedconversion ratio (FCR) as well as the protein require-mentofanendangeredcyprinid,Torputitora.Triplicategroups of ¢ngerlings with initial total length of10.0^11.0cm and weight of 12.0^12.5g were rearedinearthenpondsandfeddietsat5%ofbodyweightfor120 days. Performance was evaluated on the basis oftotal lengthgain, body weightgain, survival rate, feede⁄ciency,FCR,proteine⁄ciency ratio,speci¢cgrowthrate, energy retention, gross and net yield in kgha 1 .Whole-bodycarcass composition of ¢shwas analysedatthestartandtheendoftheexperiment.GrowthandFCRwere in£uenced signi¢cantly (Po0.05) bydietaryCP contents; higher growth and lower FCRs were ob-tainedwithincreasingdietaryprotein.Dietaryproteinalsoin£uencedthewhole-bodycarcasscompositionofthe ¢sh. Higher protein and ash, and lower moistureand lipid in the whole body were observed with in-creasingdietaryprotein.Broken-lineregressionanaly-sisindicatedthattheoptimumdietaryproteinlevelformaximal growth of mahseer lies between 45% and50% (45.3%). Overall feed utilization and growth per-formance of the ¢sh is comparable to that of otheraquaculture species and the ¢sh oiers high potentialforcommercialaquaculture.Keywords: growth,proteinrequirement,mahseer,Tor putitoraIntroductionTor putitora isahighlyprizedandwidelypopular¢shthroughout the Indian subcontinent including Ne-pal. Natural stocks of the ¢sh have been decimatedto a large extent inthe last few years resulting inanimmediate need for conservation of the ¢sh (Islam2002).Theaquaculturepotentialof the¢sh hasbeenidenti¢ed only recently. Although it is reported thatthe¢shisrelativelyslowgrowing(Pathak1991;Islam2002),thecold-lovingnatureofthe¢shoiersasuita-ble opportunity for rearing during autumn andwinter in tropical countries when traditional aqua-culture species do not grow well. Furthermore, theprobability remains that the species might performwellifpropernutritionalrequirementsaremet.How-ever, most of the aquacultureand growthcharacter-istics, particularly the dietary requirements of the¢sh, arenotwellunderstood.The signi¢cance of qualitative and quantitativeprotein in aquafeeds is well-recognized (Jauncey1982; Cho, Cowey & Watanabe1985; Shiau & Huang1989; Mohanty & Samantaray1996; Gunasekera, DeSilva, Collins, Gooley & Ingram 2000; Yang, Liou L Giri, Sahoo, Sahu & Meher 2003). Dietaryproteinrequirementofa¢shspeciesisoffundamentalimportance in aquaculture, because dietary pro-tein signi¢cantly in£uences growth, survival andyield of ¢shas wellas economics of a farming indus-try by determining the feed cost which is typicallythe largest operational cost inaquaculture. Informa-tion on the eiects of dietary protein on growthperformance as well as the dietary protein require-ments ofT. putitora is scarce, reported by only a fewworkers (Shankar 1988; Joshi, Sehgal & Malkani,1989; Sunder, Raina & Naulia1998; Islam 2002).Thepresent study reports the eiects of six levels of diet-ary protein incorporated insix iso-energeticdiets onfeed conversion ratio (FCR), growth and yield of theendangered golden mahseer,T. putitora , leading to a