Comparison of phosphorus retention efficiency between rainbow trout (Oncorhynchus mykiss) fed a commercial diet and a low fish meal based diet
2003
Satoh, S. | Hernandez, A. | Tokoro, T. | Morishita, Y. | Kiron, V. | Watanabe, T.
Aimed at developing environment-friendly aquatic feeds, a trial on rainbow trout to reduce phosphorus (P) loading is reported. Growth, feed quality performance, whole body P retention and the calculated P loading were compared between triplicate groups of fish reared with a commercial feed and an experimental diet formulated with low level of fish meal (FM, 20%) and low-P ingredients: defatted soybean meal (20%), corn gluten meal (25%) and blood meal (5%). The total P content was 18.1 and 9.9 g/kg, for the commercial and experimental diets, respectively. Fifty fish with an average weight of 1.9 g were allotted in tanks of 60 l and maintained at water temperature ranging between 12 and 20 °C. Fish were hand-fed twice a day to apparent satiety for 48 weeks. At the end of the trial, growth was comparable among fish from different treatments, although it was highest for commercial feed. Dietary treatments did not affect final specific growth rate (SGR), thermal-unit growth coefficient (TGC) or feed gain ratio (FCR). P retention levels were found to be significantly higher in the fish fed the experimental diet (35.9%) than those fed the commercial diet (18.5%). Moreover, P loading was much lower for this group than for fish fed the commercial feed (7.8 kg/ton of fish produced versus 17.3 kg/ton). The results indicate that practical low-P loading diets can be developed for rainbow trout through combinations of alternative protein sources. Furthermore, an optimal combination of diverse low-P protein sources could enhance the feed performance to a level comparable to conventional fish meal (FM) based diets.
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