|Rawles, Steven - Steve|
Submitted to: Journal of the World Aquaculture Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2012
Publication Date: 10/8/2012
Citation: Trosvik, K.A., Rawles, S.D., Thompson, K.R., Metts, L.A., Gannam, A., Twibell, R., Webster, C.D. 2012. Growth and body composition of nile tilapia, Oreochromis niloticus, fry fed organic diets containing yeast extract and soybean meal as replacements for fish meal, with and without supplemental lysine and methioninemethionine. Journal of the World Aquaculture Society. 43(5):635:647. Interpretive Summary: There is a growing segment of consumers who want organically-grown food and seafood. While the U.S. does not currently have established guidelines for organic aquaculture products, the European Union has adopted standards that are being scrutinized as a potential model for U.S. organic aquaculture. In brief, fish will most likely have to be fed fishmeal-free diets that are made from organically certified ingredients in order to be certified organic. Tilapia might fill that niche as it is one of the most farmed fish in the world with good markets in the U.S. Tilapia are also semi-herbivorous, i.e., plant-eaters, in their natural feeding habits. So it might not be difficult to develop diets composed of organic plant proteins that allow tilapia farmers to enter the organic food market. An organic diet already exists for growing tilapia once they have been moved out of the hatchery and have some size on them. But newly-hatched tilapia, called fry, require high-protein starter diets, and those diets contain high percentages of fishmeal. Two potential candidates for replacing fishmeal in fry diets are soybean meal and yeast protein. Soybean meal is the most widely-used plant-protein in animal feeds and there are plenty of organic suppliers. Yeast protein results from extracting yeast at the end of brewing and ethanol production and organic yeast protein is beginning to show up in the ingredient market. We evaluated nine different combinations of organically produced soybean meal and organic yeast protein extract as complete replacements for fishmeal in tilapia fry diets. Additionally, a duplicate set of the test diets contained added lysine and methionine because yeast protein and soybean meal are deficient in these amino acids. Without the added amino acids, fry fed the soy-yeast diets were smaller than those fed a control diet containing fishmeal. With added lysine and methionine, however, fry fed a diet containing 45% organic yeast protein and 36% organic soybean meal grew as well as fry fed the fishmeal control diet. Therefore, an organic diet is commercially feasible for tilapia fry if amino acids can be certified organic and added to the diet.
Technical Abstract: Quantities of fishmeal (FM) have remained level for the past several decades; however, demand has dramatically increased due to its inclusion in all animal production as a high quality protein source. Soybean meal (SBM) is the most widely-used plant-protein ingredient for replacing various proportions of FM in aquatic animal diets. However, use of SBM as the sole protein source has often resulted in reduced fish growth. There is a growing segment of consumers who desire organically-grown seafoods and tilapia is one of the most-cultured fish in the world. Since tilapia have herbivorous/omnivorous feeding habits, tilapia fed organic diets may allow producers to enter this rapidly-developing market. A feeding experiment was conducted to evaluate the combination of organic SBM and an organic yeast extract (YE) as complete replacements for FM in Nile tilapia, Oreochromis niloticus, fry diets. Nine diets were formulated to contain various percentages of organic YE (0, 15, 30, and 45%) in combination with organic SBM (84-34%) with and without amino acid (methionine and lysine) supplementation. At the conclusion of the study, fry fed a control diet containing 20% FM and fry fed a diet containing 45% YE/36%SBM with amino acid supplementation showed no significant differences (P > 0.05) in final weight, weight gain, and SGR compared to those fed all other diets. Based on these data, an organic diet which replaces FM with a combination of SBM and YE with added methionine and lysine is commercially feasible and further investigation into the increased use of these two ingredients as protein sources in aquaculture diets is warranted.