Six objectives will be used to improve the efficiency of trout production by the development of alternative feeds and fish better able to use those feeds. Some ingredients are developed in-house and we have both laboratory and pilot scale production capabilities. Digestibility of nutrients from specific ingredients has traditionally been conducted with large fish. The effect of strain and size will be determined. A tank system is available to collect feces both by sedimentation and stripping. The effect of strain and size on protein and amino acid retention will be conducted to determine the need for strain or life stage specific diets. Most trout culture use water from one raceway to another up to 5 times. A 36 tank system located on a commercial farm that receives water from 1st, 3rd, or 5th use will be used to determine the effect of water quality as a stressor on specific mineral and fat soluble vitamins in the tissues. A strain of trout selected to utilize plant-based diets is available and the effect of the gut microflora communities will be characterized. Fish oil has been the source of the heart/brain healthy fatty acids, EPA/DHA. This source is limited by supply and cost. Variability among trout in a specific strain for their ability to biosynthesize EPA/DHA has been identified. Trout with this trait will be bred to enhance the nutritional quality of the fillet for the benefit of the consumer. Objective 1: Develop and evaluate new ingredients and ingredient processing methods to increase nutritional and economic value. 1.A: Develop an improved soybean processing method to simultaneously separate protein and oil and remove anti-nutrients. 1.B: Development of alternative methods for the concentration of protein from wheat, barley, and oats. 1.C: Determine the nutritional and economic value of new and modified ingredients. Objective 2: Determine whether stage specific and strain specific diets are needed by evaluating nutrient digestibility at key life stages with different strains of rainbow trout. 2.A: Determination of the effect of fish size and strain on nutrient digestibility. 2.B: Evaluate the effect of fish size and strain on protein and amino acid retention efficiency. Objective 3: Improve performance of rainbow trout in serial-reuse raceway systems by improving water quality, particularly through modifications to feed formulations, and testing of fish strains. 3.A: Performance of rainbow trout in a serial-reuse system is improved by feeding diets formulated to mitigate stress. 3.B: Develop feed formulation strategies that prevent diarrhea in trout to facilitate waste management. Objective 4: Determine the genetic, physiological, and gut microflora components for improved utilization of plant-based feeds by rainbow trout. 4.A: Isolation and identification of trout microbiota and evaluation of its role in enhanced tolerance to utilization of plant-based feeds. 4.B: Determine the effect of transplantation of microbiota from selected fish. Objective 5: Develop lines of rainbow trout with enhanced abilities to biosynthesize EPA and DHA from plant oils and deposit these nutrients in muscle tissue.
Objective 1: 1.A: An improved aqueous processing method that results in high oil and protein recovery and removal of anti-nutrients will reduce the diarrheic effect of soybeans for trout. Experiments to optimize pretreatment and extraction conditions will be conducted. 1.B: Improved processing methods will increase the nutritional and economic value of protein concentrates from wheat, barley and oats. Trials will be conducted with wheat to optimize starting material and processing conditions to concentrate to 70% protein, and remove the binding effect. This effect of wheat gluten limits inclusion level in extruded feeds. Protein concentrates of barley and oats will be produced using another aqueous fractionation method that features alkaline extraction, centrifugation, and acid precipitation of supernatant. 1.C: A seven phase program will evaluate the nutritional value of alternative ingredients. Complete nutrient and anti-nutrient analysis, fry screening trials, effect on feed intake and extrusion, nutrient digestibility, growth trials, and effect on fecal size will be conducted. Objective 2: 2.A: Nutrient digestibility is affected by either fish size or strain or both. The ADC’s for major nutrients and amino acids will be determined with four unique strains of trout at three sizes (15, 500, 1500 g, 12 trials). 2.B: Nutrient retention efficiency is affected by fish size or strain or both. The same strains and fish size will be used as in 2.A in 12 week growth studies to evaluate protein and amino acid retention. Four diets varying in protein (40/45%) and lipid (20/25%) will be fed. Objective 3: 3.A: Improved diets containing elevated levels of stress-affected minerals and fat soluble vitamins will improve performance of rainbow trout raised in serial-reuse water. The effect of water source (1st, 3rd, & 5th use) as a stressor in three strains of rainbow trout on tissue concentrations of fat soluble vitamins and minerals will be determined. 3.B: Specific combinations of ingredients and prebiotics affect intestinal inflammation and the consistency of rainbow trout feces. To improve waste management dietary factors that affect fecal particle size will be determined. Objective 4: 4.A: Intestinal microflora community structure in rainbow trout is affected by diet and host genotype. Microbial communities will be identified in two strains of trout, one susceptible to soy enteritis and the other resistant. 4.B: Transplantation of microbiota from selected trout fed plant-based feed into non-selected trout will reduce intestinal enteritis when fed plant-based feeds. A cross-over experimental design will be used to determine if different microbial communities can protect a trout from soy induced intestinal enteritis. Objective 5: The ability to biosynthesize EPA and DHA in muscle tissue of rainbow trout fed diets containing plant oils can be selectively enhanced. To evaluate the potential to increase the ability of trout to biosynthesize EPA and DHA in their muscle, variation among individuals and families of rainbow trout will be determined. Individuals with known performance values for this trait will then be selectively bred.
This project builds upon the results of the previous project, 2050-21310-004-00D "Improving Sustainability of Rainbow Trout Production by Integrated Development of Improved Grains, Feeds, and Trout“ and continues to improve the efficiency and sustainability of trout production. Considerable progress was made in each of the five objectives during the first seven months of this new project. As part of Objective 1A, detailed studies were conducted on wheat protein. Wheat is one of the three major cereals and contributes almost a third of the world’s cereal protein production. Wheat is usually separated into different fractions of nutrients such as starch and protein by mechanical methods. Since the composition of protein and other nutrients varies with wheat fractions, the ability to extract protein from these fractions should differ. A study was conducted to directly compare the efficiency of extraction of protein from wheat flour, wheat bran, and whole wheat flour by aqueous solutions at varying pH values. The ultimate objective is to develop a simple method for making protein products from different wheat materials. In another study relating to Objective 1A, two wheat varieties were milled into flour and bran. Protein was extracted from the whole wheat flour using aqueous solutions having a wide range of pH values. Results show that the extraction efficiency is affected by pH of the solution. Optimizing the pH of the solution will improve the efficiency of protein extraction from different wheat products. An experiment with first feeding rainbow trout, relating to Objective 1C, was conducted to screen 11 alternative ingredients for their potential in fish feed.. These ingredients included seven varieties of soybean meal with different nutritional profiles, a meat and bone meal made from fish and poultry processing in Hawaii, a bacterial protein meal, and Asian carp meal derived from fish from the Illinois River. After 6 weeks of feeding, the trout fed the fish meal diet and the soy diets grew at the same rate. Trout fed the fish and poultry processing meal and those fed the Asian carp meal grew a little slower than the trout fed the fish meal diet but faster than the trout the Hawaiian product or the bacterial meal. As a result of this study, the manufacturer of the bacterial protein meal is making adjustments in the production process to improve fish performance. Also as part of Objective 1C, two digestibility trials were conducted to determine the nutrient availability of new ingredients. These included a field pea protein concentrate, two new sources of feed grade soy protein concentrate, a micro-alga, macadamia nut processing meal, fish and poultry processing meal from Hawaii, and four different poultry processing products. The apparent digestibility coefficients for 34 nutrients for each of these ingredients will be added to the project database that currently contains 160 entries and is posted on our website. Also evaluated was the digestibility of a diet processed by a new method to produce high moisture, water stable, soft textured feed. This feed processing technology was developed in our last project and a patent has been submitted. The feed is so water stable there is concern that digestibility might be reduced. Another set of three digestibility trials was conducted for Objective 2A. Using a commercial strain of rainbow trout the digestibility of a standard commercial type trout diet (containing fish meal and animal products) and a plant based diet was measured for fish with an average weight of 15, 500 and 1,500 grams. Since the standard method of hand stripping feces could not be used with the small 15 gram fish, a sedimentation method was used instead. Both methods of fecal collection were compared with the 500 gram average weight fish and it was found that the hand stripping method had less variation than the sedimentation method. As part of Objective 2B, a 12 week feeding trial was conducted to determine the percentage of nutrient fed (i.e. protein and amino acids) that is actually deposited in the fish. This measurement evaluates the efficiency of nutrient utilization by the fish. Both plant-based and fishmeal-based diets were fed to trout obtained from a commercial source. The study used trout averaging 15 grams per fish at the onset, and will also be conducted with fish averaging 300 and 1,000 grams. Three additional strains of fish will be compared to this commercial strain in upcoming years. To reach objective 3B we had to first develop a method to accurately and quantitatively measure fecal size and durability. Management of waste products from any animal production system is vital to the sustainability of the operation. In order to improve waste management we had to develop a method to measure the physical size and durability of fecal material. We used a laser particle size analyser to make these measurements. In an initial trial, we found that feed processing method (cooking extrusion, floating; cooking extrusion, sinking; expanded, sinking) affected both the size and durability of the feces. This information can be used to improve removal of fish wastes from the water before releasing back to the environment. Relating to objective 4A, a feeding trial was conducted to investigate the microbes living in the digestive tract of different strains of trout. This study included two strains of rainbow trout, one selected across eight generations for growth and utilization of plant-based feeds and one reared without election. The fish were grown to 5 grams and then separated into groups of 30 fish and placed into 12 tanks (6 tanks per strain). Three tanks for each group of fish were fed a fishmeal control feed and three tanks were fed a plant-based feed. After 90 days of feeding the experimental diets, five fish per tank were sampled every 30 days. Samples of distal intestine were collected for microbiota isolation as were samples for histochemical analysis. The fish have been sampled three times, with three more sample periods remaining. To reach objective 5, a feeding trial was conducted with rainbow trout from 25 families having an average weight of 15 grams. Each family was placed in a tank with 25 fish per tank. An experimental plant-based diet was formulated to contain primarily flax oil with only a minimum of fish oil (1.5%), and this diet was fed to the fish. As a control, a 26th tank with mixture of fish from all 25 families and was fed a standard fishmeal and fish oil diet. This experiment is currently underway and will be terminated when the fish reach an average weight of 250 grams. Total fatty acid levels will be analyzed to determine relative family differences in their ability to convert flax oil to the longer chain heart and brain healthy fatty acids found in wild fish.
1. Development of a quantitative method to measure fish fecal particle size and durability. The presence of fish waste in fish farm effluent is a major constraint to the expansion of the industry. Also, very small fecal particles suspended in the water are difficult to remove, and reduce water quality and fish well-being. ARS scientists with the Small Grains and Potato Germplasm Research Unit in Aberdeen, Idaho, developed a method using laser diffraction technology to accurately quantify fecal particle size and the durability. This new method enables measurement of dietary factors that affect fecal size and durability and will aid in the optimization of diets to improve waste management, improve rearing water quality and fish health, and improve the quality of water returning to the natural environment.
Johnson, R.B., Kim, S., Watson, A.M., Barrows, F., Kroeger, E.L., Nicklason, P.M. 2015. Effect of dietary taurine supplementation on growth, feed efficiency, and nutrient composition of juvenile sablefish (Anoplopoma fimbria). Aquaculture. 445:79-85.