Interactive effects of dietary ascorbic acid and density on growth parameters of rainbow trout (Oncorhynchus mykiss)

This study was conducted to evaluate the interactive effects of different levels of dietary ascorbic acid and density on growth parameters of rainbow trout. The eighty- one rainbow trout broodstock (812 ± 1.5 g) distributed into six groups as experimental treatments and were fed different levels of ascorbic acid including 0, 100 and 1000 mg/kg L-ascorbyl-2-polyphosphate. The feeding trial was carried out in two different densities (3 and 6 fish/m3) for a 16- week period in triplicates. Each diet was fed to triplicate groups of fish to apparent satiation two times a day. Changes of body weight increase were observed from fourth week to 12th week. The highest amounts of weight gain and specific growth rate were observed in high density (6 fish/m3), but no significant difference was observed between 100 and 1000 mg/kg ascorbic acid in high density. At the end of the experiment, fish fed −C diet had a lowest final mean weight (885.2 ± 2.09 g) than those fed +C diet. These results indicated that dietary ascorbic acid significantly influenced growth performance of rainbow trout broodstock, especially in high density and the level of 100 mg ascorbic acid per kilogram diet can lead to desirable growth of female rainbow trout breeders.