Submitted to: Aquaculture Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/21/2007
Publication Date: 10/9/2007
Citation: Barrows, F., Gaylord, T.G., Stone, D.J., Smith, C.E. 2007. Effect of protein source and nutrient density on growth efficiency of rainbow trout (Oncorhynchus mykiss). Aquaculture Research.38:1747-1758
Interpretive Summary: Fish meal has been the primary protein source in trout diets for many years. Fish meal is produced form the ocean harvest of species such as sardines, herring or menhaden, and this harvest is at maximum sustainable limit. Incorporation of plant-derived ingredients into fish diets is necessary for the continued viability of aquaculture and to produce new markets for grain producers. A study was conducted to determine the effect of protein source and nutrient density on growth of rainbow trout over 12 weeks. Growth rate of fish fed one of 6 fish-meal free, plant-based feed was compared to fish fed one of two fish-meal based diets. The nutrients in the plant-based diets were slightly less digestible than the fish-meal based diets, and this was reflected in slightly slower yet comparable growth. The nutrients in diets comprised of plant concentrates produced from soybeans and wheat are highly digestible, and are similar to fish-meal based diets. Lower nutrient digestibilties were observed for diets composed of un-refined plant meals or animal by-products. Increasing the dietary concentration of energy and protein did not increase growth, but did improve the efficiency of growth. This study provides further evidence that growth rates of trout fed fish-meal free diets, using conventional and concentrated plant protein ingredients, can be comparable to trout fed fish meal based feeds.
Technical Abstract: The effect of protein source and nutrient density on growth efficiency, nutrient digestibility and plasma amino acid concentrations of rainbow trout were evaluated over 12 weeks. A 4 by 2 factorial treatment design with four protein sources (fishmeal/barley, plant concentrates, plant meals, animal/plant-no fish) and two nutrient densities (43% protein/13% fat, and 48% protein/18% fat) was used. Six of these diets were fish meal free, and a reference diet (commercial fish-meal based trout diet) and a control diet (fish meal/wheat flour based) were fed. Protein source and nutrient density affected feed intake, weight gain, and feed conversion ratio. Weight gain of fish fed three of the fish-meal free diets was equivalent to fish fed the fish-meal based diets. Protein retention was affected by protein source, but not nutrient density, and was highest for the fish fed diets containing fish meal and lowest for the fish fed diets containing plant meals. Differences in weight gain were reflected by differences in apparent digestibility coefficients and apparent amino acid availabilities. This study provides further evidence that growth rates of trout fed fish-meal free diets, using conventional and concentrated plant protein ingredients, can be comparable to trout fed fish meal based feeds.