Effect of growth rate on quality traits and feed ž / utilisation of rainbow trout

Ž . Rainbow trout Oncorhynchus mykiss of initial average weight 150 g and brook trout Ž . SalÕelinus fontinalis initially weighing 124 g on average, were reared at different growth rates Ž . Ž . by feeding either a high H, close to satiation or low L, half of H ration of a commercial diet. Fish were reared for 6 to 15 weeks in order to reach same size class. Fast growth increased whole Ž . Ž . body lipid and dry matter P-0.01 but reduced ash in both species P-0.01 . Brook trout were both more fat and had higher protein content, lower moisture and lower ash content than the Ž . Ž rainbow trout P-0.01 . Neither the feed conversion ratio FCRsg feed intakeP g weight y1. Ž . increase nor protein retention efficiency PRE was affected by growth rate. The brook trout, Ž . however, were more efficient in retaining protein than the rainbow trout P-0.01 . Enhanced Ž . growth increased fat content in fillets P-0.01 . Like in whole body protein and dry matter was Ž . higher P-0.01 in brook trout fillets than in fillets from rainbow trout. Carcass percentage was Ž . in overall lower P-0.01 at high growth rates compared to slow growth while both carcass Ž . Ž . percentage P-0.01 and fillet yield P-0.01 was lower in brook trout than in rainbow trout. q 2000 Elsevier Science B.V. All rights reserved.