Submitted to: Annual Meeting World Aquaculture Society
Publication Type: Abstract only
Publication Acceptance Date: 9/1/2005
Publication Date: 2/13/2006
Citation: Barrows, F., Gaylord, T.G. 2006. Recent results with a plant-based trout feed and review of work on novel protein sources for trout. Annual Meeting World Aquaculture Society. Interpretive Summary: Several approaches are being used to replace fish-meal harvested from the ocean with plant-derived ingredients. One study demonstrated that trout growth is not reduced when fish meal is replaced with either plant protein concentrates or plant meals. The cost of these feeds were higher, however, so alternate ingredients are being investigated. Soybean meal produced as a by-product to bio-diesel production was evaluated as a replacement for conventional soy-bean meal. The new extraction method used in the bio-diesel soybean meal did not affect growth rate of rainbow trout. As the bio-diesel industry expands more of this meal may be available and can be used in trout diets. Soybean meal and barley meal are too low in protein to be included at high levels in trout feeds. To produce a high protein plant ingredient these two seeds were mixed and fermented using innovative mass production methods. The result is a high protein, highly digestible plant-derived protein source. This ingredient, however, has low palatability to fish and may be more appropriate for other species. Studies are underway to modify the product for increased palatability to trout.
Technical Abstract: A study was conducted to evaluate the effect of protein source and nutrient density on fish growth, feed efficiency, digestibility and plasma amino acid concentrations. A four by two factorial treatment arrangement with four protein sources (fishmeal/barley, plant concentrates, plant meals, animal and plant/ no fish) and two nutrient densities was used. Six of these feeds are fish meal free. Two additional control feeds were fed, a commercial fish-meal trout feed and a fish meal/wheat flour feed. Rainbow trout (House Creek strain, College of Southern Idaho; approximately 20 g initial weight) cultured in 145-L liter fiberglass tanks (50 fish/tank; 3 tank/diet) in a fresh water flow through system (spring water, 14.5ºC at 4L/min) were fed the test diets fed by hand to satiation for 12 weeks. At termination, 10 fish/tank were sampled for determination of proximate composition and blood from 5 fish/tank was collected for determination of amino acid concentrations. There was a significant effect of protein source, but not nutrient density, on fish growth. Growth rate of fish fed 3 of the plant-based diets were equal to the fish fed the fish meal control diet. Nutrient density did have an effect on feed efficiency, with the higher protein and energy levels resulting in higher feed efficiency. Dietary nutrient digestibly, and plasma amino acid concentrations will also be discussed with reference to fish growth and feed efficiency.