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United States Department of Agriculture

Agricultural Research Service

Research Project: Improving Sustainability of Rainbow Trout Production by Integrated Development of Improved Grains, Feeds, and Trout

Location: Small Grains and Potato Germplasm Research

2013 Annual Report

1a. Objectives (from AD-416):
The objective of this research is to improve the sustainability and production efficiency of rainbow trout by developing innovative feeds that reduce dependence on marine fishery resources. Objective 1: Identify and develop grain lines with desirable traits for either direct or indirect use in aquafeeds. Objective 2: Develop mechanical, chemical and biological methods to improve the nutritional and anti-nutritional profile of grains, by-products and other alternative ingredients. Objective 3: Determine nutritional value of alternative ingredients (protein, lipid, energy) and develop practical feed formulations for improved strains of fish. Objective 4: Determine optimal nutrient supplementation levels for specific life stages of improved strains of trout. Objective 5: Use gene expression analyses to advance the understanding of gene targets for improving nutrition, growth, and development processes under production conditions. Objective 6: Identify phenotypic differences in rainbow trout for growth and utilization of plant-based sustainable diets and determine the genetic variation for the identified traits.

1b. Approach (from AD-416):
A multidisciplinary approach will used combining expertise in the fields of plant genetics, grain processing, fish nutrition and physiology, and fish genetics. Grain lines will be identified that have traits desirable for fish feeds. Phenotypic differences in trout for their ability to utilize plant-based feeds will also be identified. Grains will be further modified through physical, biological or chemical methods to improve their nutritional profile for trout. Feeds will be formulated using alternative ingredients to fish meal and to meet the nutritional requirements for improved strains of trout This project will benefit; fish farmers through improved feeds and environmental compliance through reduced nutrient release, identified traits and markers to aid stock improvement efforts, feed manufacturers with alternate ingredients, reduced costs, price stability, and improved diet formulations, and grain farmers with new markets and products, and the consumer with a safe, sustainable, nutritious food supply and cleaner environment. FY99 Program Increase $225,000 Add 1 SY for research on cereal grains & fish FY03 Program Increase $223,537 Add 1 SY FY04 Program Increase $241,566 Add 1 SY FY04 Program Increase $584,232 Add 1 SY FY05 Program Increase $111,600 Replaces 5366-21310-002-00D (12/04). FY06 Program Increase $89,100 Replacing 5366-21310-003-00D 12/11/2009.

3. Progress Report:
Progress was made on Obj. 2-6, and Obj. 1 is not active due to critical personnel vacancy which will not be refilled. Under Objective 2.A, we made significant progress in the development and production of a protein concentrate from oats. Pilot scale quantities were produced and both a digestibility trial with adult rainbow trout and a feeding trial with first feeding rainbow trout were conducted. Progress was made in Objective 2.b, in the fractionization of distillers dry grains with solubles. Pilot scale quantities of both a phosphorus and protein co-product were produced and an invention disclosure was submitted and approved. Feeding trials with trout indicate the protein co-product is highly palatable and digestible. Feeding the phosphorus supplement to young trout resulted in growth depression, perhaps due to concentration of other trace minerals. Research is underway to further improve the product. Under Obj. 3a we made significant progress by determining the availability of nutrients in 26 ingredients to rainbow trout. This information was added to our on-line database. First feeding trout trials screened an additional 32 ingredients to determine if ingredients warrant further evaluation. The technology and information developed in Objective 2 and 3.a, were applied to objective 3.b and significant progress was made. Plant-based and fish meal free diets have been shown to be effective trout for several years, and were applied to Coho salmon and yellowtail, two high value species previously considered carnivorous and to require fish meal. Feeding studies with Yellowtail (known as Kampachi in sushi markets) were conducted at a commercial site in Hawaii, and Coho studies were conducted in-house. Under Objective 4, we conducted an additional trial to determine the optimal supplementation level of zinc to plant based diets for trout. Thirty mg/kg of zinc is required by young trout fed plant based diets for optimal growth and health. For Sub-objectives 4.B and 5.C, construction of the serial reuse system has been completed, and the system has been tested and validated. Trout have been stocked, and the protein source study for Sub-objective 4.B is currently underway. Under objective 5, we developed a panel of metabolic related genes which is being validated to monitor growth and feed conversion in rainbow trout families selected for utilization of a plant-based diet. For sub-objective 5b, genomic libraries are currently being produced from selected and unselected trout lines from three different tissues. Upon completion of libraries they will be sequenced and analyzed for markers linked to enhanced dietary utilization. Under objective 6, we have identified physiological differences related to intestinal tolerance of plant proteins between selected and non-selected lines of rainbow trout and are following this up with sequence analysis between these lines. As part of sub-objective 6.b we have determined that variation exists both between individuals and families of trout for their ability to convert plant oils to the heart healthy fatty acids found in fish oil and then deposit these fatty acids in the muscle tissue.

4. Accomplishments
1. Method to produce feed grade soy protein concentrate shown to be effective for trout. Soy protein concentrate has been used as an ingredient in fish feeds for years, but only food grade product is available in the US. Scientists with the Small Grains and Potato Germplasm Research Unit in Aberdeen, Idaho, developed a low cost method for increasing the protein in soybean meal from ~46% to over 60% and eliminating compounds detrimental to fish. Trout feeding studies have demonstrated high digestibility, palatability and growth of first feeding and juvenile trout. This technology is currently being negotiated for licensing. Development of a U.S. soy protein concentrate will benefit soy farmers and consumers, and will increase the profitability and sustainability of aquaculture production.

2. Fish meal-free diets developed for Coho Salmon and Yellowtail. Fish meal has been the primary protein ingredient in fish feeds for decades but increasing demand and static supply is limiting expansion of aquaculture production. Scientists with the Small Grains and Potato Germplasm Research Unit in Aberdeen, Idaho, applied information and technology developed with rainbow trout to two marine species. Feeding studies with each species demonstrated that as long as all essential nutrients are supplied and balanced, fish meal is not needed for optimal growth and health of the fish. Reducing or eliminating the dependence of aquaculture feeds on marine harvested ingredients will increase profitability and sustainability of aquaculture.

3. Determination of variation in rainbow trout for production of healthy omega-3 fatty acids. The increase in price and static supply of fish oil is forcing aquaculture to find alternative and sustainable oil sources to substitute for fish oil in aquaculture feeds. The problem is that removal of fish oil from the diets of these fish restricts the level of heart healthy omega-3 fatty acids in the fillet which decreases benefit to the consumers. In prior studies we have determined that variation exists between families and that genetic improvement through selection is possible. During the last year we have determined there is variation within family’s as well and validated methods for measuring fatty acid levels in live fish. This methodology will provide us with the ability to accurately assess improvement through breeding, determine the physiological basis behind the trait, and ultimately produce a fish with greater health benefits.

Review Publications
Ohs, C.L., Dimaggio, M.A., Grabe, S.W., Broach, J.S., Watson, C.A., Breen, N.E., Barrows, F. 2013. Effects of increasing docosahexaenoic acid and arachidonic acid in brood diets of monodactylus sebae on fecundity, egg and larval quality, and egg fatty acid composition. North American Journal of Aquaculture. 75:285-294, 2013.

Rawles, S.D., Fuller, S.A., Beck, B.H., Gaylord, T.G., Barrows, F., McEntire, M.E. 2013. Lysine optimization of a commercial fishmeal-free diet for hybrid striped bass (Morone chrysops x M. saxatilis). Aquaculture. 396-399:89-101.

Liu, K., Barrows, F. 2013. Methods to recover value-added co-products from dry grind processing of grains into fuel ethanol. Journal of Agricultural and Food Chemistry. 61.7325-7332.

Last Modified: 06/25/2017
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