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 be 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.
3. Progress Report
Progress was made on all 6 objectives, all of which fall under National Program 106, in Component 1, Understanding, Improving, and Effectively Using Animal Genetic and Genomic Resources, Component 2, Enhancing Animal Performance, Well-being, and Efficiency in Diverse Production Systems, or Component 3, Defining Nutrient Requirements and Nutrient Composition of Feedstuffs and Expanding Alternative Ingredients. Under objective 1B, Develop and Implement Genetic Improvement Programs, we made significant progress in identifying families of trout that demonstrate improved growth and feed efficiency when fed plant-based feeds, compared to unselected trout fed the same diets. This research was conducted both in-house and at a commercial 3rd party site. Progress has also been made under Objective 2A, Improve Growth, Nutrient Utilization, and Well-being to understand the role of feed composition and genetics in protein and energy retention. Interactions of trout family by diet composition on nutrient retention have been investigated and the selected fish have improved protein retention, but not energy retention, compared to the unselected strains. Under objective 3A, Determine Nutrient Requirements, studies have been completed to determine the optimal supplementation level of copper, magenesium and zinc to plant-based or fish meal based diets. Progress was made in several areas under Objective 3b, Evaluate the Nutritional Value of Alternative Sources of Protein and Lipid. Several studies have been conducted examining the processing characteristics and nutritional value of improved lines of soybeans, and 3 forms of corn protein concentrate. A method was also developed to produce a feed grade soy protein concentrate. Significant progress has been made at increasing production to a pilot scale. To assist in supplying affordable grain based products for aquafeeds, two high beta-glucan varieties of barley were developed. Beta-glucan is beneficial for trout under stressful conditions and is also need in the human nutracuetical industry. Distiller dried grains with solubles (DDGS) is a co-product of industrial ethanol production from corn and other cereal grains. Methods have been developed to improve the nutritional value of DDGS for aquafeeds. Laboratory results have been transferred to industry by conducting “on-farm” trials with commercial trout producers evaluating alternative protein ingredients. Significant progress was made in the development of Alternative Feeds by combining the results of many studies with trout and applying them to other commercially important species including Atlantic salmon, arctic char, cobia, yellowtail, and white seabass and evaluated in extended growth studies. Good growth and feed conversions were observed further proving that aquaculture feeds can utilize high levels of plant ingredients and do not need to depend on fish meal. A trial is currently underway and pilot screening conducted at a commercial trout farm, evaluating fish meal and fish oil free diets. The essential fatty acids for the fish are supplied by algal sources.
1. ARS trout lines incorporated into commercial lines. Plant-based fish feed reduces dependence on marine fishery resources. ARS researchers in Hagerman, Idaho, have selected lines of rainbow trout for several generations for improved performance when fed fish-meal free, barley containing diets. Working jointly with their CRADA partner, these trout were incorporated into the breeding program. During the next production cycle these fish will account for at least 15% of commercially produced rainbow trout in the United States. Improved genetic trout lines from the ARS broodstock program are available to the trout industry and to trout researchers nationwide.
2. Development of a standardized digestibility database for traditional and alternative feed ingredients. In order to successfully substitute ingredients in fish feed diets, the availability of the nutrient needs to be known. This information is not available using standarized laboratory methods with commercial processing. ARS scientists in Hagerman, ID, compiled a first of its kind database with 80 ingredients and digestibility coefficients for macro-nutrient, amino acids, and minerals for rainbow trout and 26 ingredients for hybrid bass. This information has been transfered to commercial feed producers and is posted on the internet and will allow for more efficient feed utilization by the aquaculture industry.
3. New analytical method developed for measuring the degree of starch gelatinization. Starch gelatinization plays an important role in determining the structural and textural properties of processed foods and feeds. It also affects human and animal nutrition through changing enzymatic access to glucosidic linkages and consequent digestibility of starch. Several methods are available to measure the degree of starch gelatinization, but some of them require costly instrumentations while others are applicable only to purified starch. ARS researchers at Aberdeen, Idaho, have developed a new rapid and low cost enzymatic method that can measure the degree of starch gelatinization, not only for purified starch, but also for processed feed or food. This new method will speed development of new feeds.
4. Identification of potential commercial use for the low beta-glucan line of M351. Beta-glucan decreases the processing efficiency of ethanol production with barley. We have identified a low beta-glucan barley line from our mutant treatment materials and are working in collaboration with the National Corn to Ethanol Research Center (NCERC). The test results showed that M351 produced significantly better quality of feed by-product without compromising the ethanol production. The demonstrated higher value of the M351 has resulted in a material transfer agreement with Osage Bio-energy Inc.Liu, K. 2011. Chemical composition of distillers grains, a review. Journal of Agricultural and Food Chemistry. 59:1508-1526.