Abstract
Background:Alternative protein sources to fishmeal in fish feeds are needed.Objectives:Evaluate rearing performance of adult rainbow trout (Oncorhynchus mykiss) (initial weight 139.0 ±1.5 g, length 232.9 ± 0.8 mm, mean ± SE) fed one of the two isonitrogenous and isocaloric diets (46% protein, 16% lipid) and reared at one of the two levels of exercise (water velocities of either 3.6 cm/s or 33.2 cm/s).Methods:Protein in the control diet was based on fishmeal. In the experimental diet, bioprocessed soybean meal replaced approximately 60% of the fishmeal. Fish were fed by hand once-per-day to near satiation, and the food was increased daily. The experiment lasted 90-days.Results:There were no significant differences in gain, percent gain, or specific growth rate between the dietary treatments. However, the amount of food fed and feed conversion ratio was significantly lower in the 60% bioprocessed soybean meal diet. Intestinal morphology, relative fin length, splenosomatic index, hepatosomatic index, and viscerosomatic index were not significantly different in the trout fed either diet. Fish reared at 3.6 cm/s had a significantly lower feed conversion ratio (1.02 ± 0.02) than fish reared at 33.2 cm/s (1.13 ± 0.02). However, there were no significant differences in gain, percent gain, specific growth rate, or percentage mortality in fish reared with or without exercise. No significant interactions were observed between diet and exercise (higher water velocity).Conclusion:Based on these results, at least 60% of the fishmeal in adult rainbow trout diets can be replaced by bioprocessed soybean meal, even if higher water velocities are used to exercise the fish.
Highlights
The use of soybean (Glycine max) meal in carnivorous fish diets has been subjected to considerable research [1, 2]
Based on these results, at least 60% of the fishmeal in adult rainbow trout diets can be replaced by bioprocessed soybean meal, even if higher water velocities are used to exercise the fish
There were no significant differences in gain, percent gain, Specific Growth Rate (SGR), and percent mortality between the tanks of fish receiving the fishmeal reference diet or the 60% bioprocessed soybean meal (BSM) diet at the end of the experiment (Table 4)
Summary
The use of soybean (Glycine max) meal in carnivorous fish diets has been subjected to considerable research [1, 2]. Just as dietary ingredients can impact fish growth, using higher water velocities to exercise fish can positively impact rearing performance [17 - 20]. A few studies evaluating forms of bioprocessed soybean meal (BSM) in rainbow trout diets have been conducted, but novel BSM products continue to be developed. Very little research has been published examining the potential interaction between exercise (increased water velocities) and diet, in relation to non-fishmeal based diets in any fish species. The objective of this study was to evaluate the use of a propriety BSM product as the primary dietary protein source, in conjunction with exercise (increased water velocity), during rainbow trout rearing. Alternative protein sources to fishmeal in fish feeds are needed
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