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RESEARCH PRODUCT

Effects of feeding frequency on growth and food utilisation of rainbow trout (Oncorhynchus mykiss) fed low-fat herring or dry pellets

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Abstract One-year-old rainbow trout (weight range 400–700 g) were fed for 18 weeks on low-fat herring or commercial dry pellets 1, 2 or 4 times in a day. Quadratic regression analysis indicated that at least three feedings were required for maximum growth and that fish fed a dry diet could benefit from even more frequent feeding. The proportion of lipid in growth increased with increased number of feedings, but the protein content was not affected (mean 18.6% protein wet basis). Food consumption (dry weight) was affected in a similar manner for both diets and its maximum occurred at slightly higher frequency than for maximum growth. No effects of feeding frequency or type of diet on energy retention efficiency were observed (mean 42.5% of gross energy) but protein efficiency decreased with more frequent feedings. Dry diet protein was retained more efficiently than protein from herring. It is suggested that the number of feedings required for maximum growth may be dependent on the nutrient density of diet.