Growth and feed conversion of juvenile winter flounder (Pleuronectes americanus) in relation to different protein-to-lipid levels in isocaloric diets

摘要

Winter flounder show good potential for culture in Atlantic Canada. Information about their nutritional requirements is necessary in order to be able to formulate cost-effective feeds that produce acceptable growth rates. Fish meal, the principal protein source in most fish feeds, is one of the more expensive ingredients. Reduction of the amount of protein in diets would reduce the cost of feed. Therefore, a 10-week feeding trial was conducted with juvenile winter flounder (initial weight 0.8 g) in order to determine the effect of reducing digestible protein-to-energy levels in diets on specific growth rates (SGR), feed efficiency (FE) and respiration rates. Experimental diets were formulated to contain dietary protein-to-lipid levels of 50:10%, 45:15% and 40:20%. There were significant differences in final weights and percent weight gain among all three dietary treatments. Winter flounder fed the 50: 10 diet (26.6 mg kJ(-1) digestible protein to energy) had the highest specific growth rate (2.1 +/- 0.2% weight day(-1)), which was significantly greater (P < 0.05) than those receiving the 40:20 diet, 20.9 mg kJ(-1) (1.1 +/- 0.3% day(-1)), but not significantly different from those that fed the 45:15, 23.5 mg kJ(-1) diet (1.7%). The 50:10 diet-fed fish had a feed efficiency ratio (0.7 +/- 0.1) which was significantly better than the 40:20 group (0.2 +/- 0.1, P < 0.05), but not significantly different from the 45:15 diet-fed fish (0.5 +/- 0.1). While not significantly different (P = 0.06), the protein efficiency of the 50: 10 diet-fed fish tended to be higher than the other two groups.