Feed regimen affects growth, condition index, proximate analysis and myocyte ultrastructure of juvenile spinefoot rabbitfish Siganus rivulatus

The present work was designed to evaluate the effects of various feeding regimens on rabbitfish growth and condition. Twelve juvenile rabbitfish Siganus rivulatus (7.3 +/- 0.1 g) were stocked into each of 15 tanks. Tanks were randomly assigned one of five treatments with three replicate tanks per treatment. Treatments were G-I: fish fed once daily at 08.00; G-II: fish fed once daily at 17.00; G-III: fish fed twice daily at 08.00, 17.00; G-IV: fish fed three times daily, at 08.00, 13.00, 17.00; G-V: fish fed three times daily at 08.00, 13.00, 17.00 for six consecutive days, followed by 1 day of fasting. Fish were offered a commercial diet (Golden Extruded, 450 g kg(-1) protein, 200 g kg(-1) lipids) to apparent satiation. At the conclusion of the study, weight gain of rabbitfish fed three times daily (273.1%) was significantly greater than weight gain of fish in all other treatments. Feed conversion ratio (FCR) of fish fed once per day (1.5) was significantly greater than FCR in all other treatments. Proportion of lipids in fish fed three times per day was significantly greater than in fish from other treatments. Ultrastructure of muscle of fish offered feed three times daily had a better organized appearance and better defined striation than muscle of fish in other treatments. Accordingly, feeding rabbitfish three times daily is better than feeding them once or twice daily and also improves muscle ultrastructure and quality.