Location: Harry K. Dupree Stuttgart National Aquaculture Research Cntr
2017 Annual Report
Objectives
Objective 1: Develop novel ingredients and formulate diets for warmwater finfish. Novel ingredients and new formulations will target reduced reliance on fishmeal in the diets, enhanced nutrient delivery (e.g., better amino acid availability), and reduced anti-nutritional factors.
Sub-objective 1A: Develop and validate practical all-plant protein diets for hybrid striped bass (HSB) and white bass.
Sub-objective 1B: Determine optimal inclusion level of distiller’s dried grains with solubles and high-protein distillers dried grains with solubles in diets for Nile tilapia.
Sub-objective 1C: Determine optimal inclusion level of cottonseed meal and poultry by-product meal in diets for largemouth bass.
Objective 2: Obtain and test white bass broodfish from multiple populations for improved production of hybrid striped bass. Key phenotypic traits will be defined and a white bass broodstock will be established.
Sub-objective 2A: Obtain and produce white bass from multiple geographically distinct populations.
Sub-objective 2B: Conduct white bass strain performance evaluation and selection.
Sub-objective 2C: Hybrid striped bass performance evaluation.
Objective 3: Compare and optimize production of hybrid striped bass in biofloc technology and pond production systems.
Sub-objective 3A: Define stocking rate/initial biomass – yield relationship for HSB in a biofloc technology system.
Sub-objective 3B: Compare production of HSB in biofloc technology and pond production systems.
Approach
Identify promising feed palatants that enhance all plant protein (APP) diet feed intake; identify plant proteins for use in APP test diets; formulate a series of marine fish meal (FM) replacement diets using ideal protein theory, plant protein blends, and feed additives designed to ameliorate ingredient deficiencies; characterize growth performance, nutrient retention, gut microflora, and metabolic gene expression in response to FM replacement diet; and validate promising APP diets in a pond production trial. Feeding studies will evaluate the effect of partial or total replacement of FM by either Distiller’s dried grains with solubles or high protein Distiller’s dried grains with solubles in the diet of Nile tilapia on feed intake, growth, feed conversion, and histology of the intestine. A feeding study will evaluate the effect of substitution of FM by various ratios of poultry by-product meal and cottonseed meal in practical diets for juvenile largemouth bass on growth performance, health status, and body composition. Adult white bass (WB) will be acquired from three distinct regions of the species’ native range (Arkansas River, AR, Central and South TX, and Upper Tennessee River, TN), spawned and the genetic diversity and production performance of multiple strains and families will be compared in tanks and ponds to our domesticated WB broodfish population in order to select superior performing families to use in developing improved synthetic lines. Evaluate production performance of families of hybrid striped bass (HSB) made from the WB improved synthetic lines. Quantify the relationship between the HSB stocking rate/initial biomass – yield relationship to produce advanced fingerlings in the biofloc technology production system and compare to traditional pond production method.
Progress Report
Studies were completed to evaluate the efficacy of feeding stimulants, i.e., palatability enhancers or “palatants” that are typically used to stimulate intake of manufactured feed in fish. As fish diets become less animal meal based and more plant-based, poor feed intake becomes a major bottleneck in the production of some fish and slows producer acceptance of plant-based feeds that are more sustainable. A series of short, 5-day palatability trials were conducted with juvenile hybrid striped bass to assess feed intake of a plant-based diet supplemented with one or more palatants of interest in comparison to unsupplemented plant diets and a well-accepted commercial diet. The compounds of interest include: betaine (trimethylglycine), carboxylic acids, crawfish oil, dimethyl-B-propiothetin (DMPT)/dimethylsulfonyl propionate (DMSP), garlic, inositol monophosphate (IMP), liver by-products, molasses, feed-grade nucleotides, poultry fat, ProOmega 55™, and shrimp oil. (Objective 1)
ARS researchers feel that white bass (WB) may be a valuable domestic food-fish, yet are under-represented in U.S. aquaculture. There is extremely limited data on nutritional requirements of this fish, and on use of different culture methods that might optimize production and improve farm diversity and profitability. Cage culture allows for the growing of fish in ponds that may otherwise be difficult to harvest, either due to irregularly-shaped pond bottoms, shape of the pond, or presence of debris and obstacles on the pond bottom. To investigate whether white bass can be grown in cages with acceptable growth rates and high (>85%) percentage survival, we completed in October 2016 a study to determine the effects of different stocking densities on growth, body composition, and fillet proximate composition. The culture trial was conducted in 12 cages (3.5 m3; 1.2 x 2.4 x 1.2 m). White bass juvenile (60 g) were stocked into nylon-mesh floating cages at four different rates (100, 200, 300, and 400 fish/cage) and were being fed a commercial diet that meets all known nutrient requirements for bass. Sample and data analyses are in progress. (Objectives 1 and 2)
Significant progress was made in a subordinate project at ARS Stuttgart, Arkansas, to replace fish meal in commercial hybrid striped bass diets with newly developed protein blends. Phase one of the two-phase project with a feed ingredient supplier determined the availability of nutrients (protein, lipid, amino acids, minerals, and energy) in four commercial protein blends of interest. In phase 2 beginning this year, digestibility coefficients developed in phase 1 will be used to formulate test diets for an ingredient performance trial in hybrid striped bass. Fish meal in a typical diet will be replaced with each of the protein blends and supplemented with potentially limiting nutrients based on the latest diet formulation theory. The feeding trial will reveal performance advantages, or differences, of the commercial blends in comparison to fish meal, as well as potential strategies for modifying the composition of the blends for greater performance and cost savings. (Objective 2)
To better understand gut microbe dynamics of tilapia under various culture conditions and dietary treatments, ARS scientists at Stuttgart, Arkansas, and Hagerman, Idaho, in collaboration with researchers at Wageningen University, Netherlands, mapped the gut microbial communities in early life tilapia larvae grown in various culture environments with and without probiotic treatment. Additionally, gut microbial communities were mapped in tilapia fed a sludge-infused diet. Generated microbial datasets were released to the public. (Objectives 1 and 3)
We successfully produced 71 experimental crosses from amongst each of the five wild white bass strains and the domestic white bass strain resulting in over 3.6 million fry. The resulting fry are being raised in preparation for inclusion in Fall 2017 production performance trials. Broodfish are currently being conditioned for the next phase of the plan in FY 18. (Objective 2)
Working closely with researchers at Auburn University (School of Fisheries, Aquaculture, and Aquatic Sciences; Center for Advanced Science, Innovation, and Commerce), ARS researchers in Stuttgart, Arkansas, are currently examining the genetic relationships, using high-throughput genotyping-by-sequencing (GBS), between the domestic white bass currently housed at Stuttgart and five populations of white bass collected by ARS researchers from drainages in Arkansas, Texas, and Alabama. These analyses are expected to generate over 5,000 high quality single nucleotide polymorphism (SNP) markers suitable for downstream applied applications in broodstock selection and parentage analyses for cultured white bass populations. These markers will greatly enhance researchers’ ability to create, evaluate, and maintain improved lines of hybrid striped bass for the benefit of the burgeoning hybrid striped bass industry. (Objective 2)
Hatchery-reared tilapia, which is the sole source available to U.S. farmers, weigh about 0.2 ounces when purchased by the farmer. Stocking these small fingerlings into food fish production units is an inefficient use of production inputs, but is practiced by many farmers. More efficient use of production inputs would be to produce an advanced fingerling using more intensive production practices such as the biofloc technology (BFT) production system. We initiated in May 2017 a follow-on an extended range-finding experiment to quantify the relationship between fingerling tilapia growth and yield, and stocking rate in the outdoor BFT production system. Fish will be grown until October 2017. Results from this and a previous study should demonstrate the optimal stocking rate to produce an advanced fingerling. (Objective 3)
Tilapia grown in the BFT production system are able to derive nutrition by consuming the biofloc and because of this some researchers advocate lowering the protein content of formulated rations. However, the optimal protein content has not been determined for tilapia in BFT production. We completed a study October 2016 to quantify the relationship between formulated diet protein content and tilapia growth (to a 1-lb market size) and yield, and water quality in an outdoor BFT production system. We used the ratios and levels of essential amino acids in tilapia muscle, i.e., the ideal protein model we chose, as the targets for optimizing diet formulations. Diets were formulated using the digestible, as opposed to total, nutrient levels found in the feed ingredients and supplemented with limiting essential amino acids to meet the target levels suggested by the muscle profile. (Objective 3)
Fish feed typically is supplemented with inorganic phosphorus (e.g., dicalcium phosphate) to ensure adequate dietary phosphorus availability, especially in diets that contain high percentages of plant feedstuffs, which is the case for diets formulated for tilapia. Phosphorus is present in plant feedstuffs as phytate, which is not bioavailable to fish because their digestive system lacks sufficient phytase enzyme. Thus, phytate is excreted unmetabolized and accumulates to high concentrations in the BFT production system because of the high quantities of feed fed daily to fish. In May 2017, we initiated a study in an outdoor BFT production system to investigate the impact of dietary inclusion of phytase on phosphorus retention by tilapia and on water quality. Three diets were formulated: the positive control diet, which gave the best results in our 2016 tilapia BFT experiment, contains supplemental inorganic phosphorus to meet the tilapia dietary requirement of available phosphorus; the negative control diet, which is the positive control diet without supplemental inorganic phosphorus; and, phytase diet, which is the negative control diet supplemented with phytase. All diets will contain 27.7% digestible protein and 6% lipid. The production goal for this study is to produce a market-size fish (minimum of 454g or 1lb) by the end of our growing season in October 2017. (Objective 3)
Accomplishments
1. Feed palatants for all-plant hybrid striped bass diets. Plant-based aquaculture feeds are more sustainable than fish meal or animal product-based feeds, and increasingly desired by millennial generation fish consumers. However, as fish diets become more plant-based, hybrid striped bass reject the flavor, feed consumption drops dramatically, and fish production and performance suffer. ARS researchers at Stuttgart, Arkansas, assessed feed intake of an all-plant diet supplemented with one or more flavor attractants of interest and compared that to feed consumption of an un-supplemented plant diet, as well as to a well-accepted commercial diet (containing fish meal). The attractants, or “palatants” as these potential feed stimulants are called, include natural plant and animal extracts, or blends, that increase feed consumption in some land animals. In short feeding trials with juvenile hybrid striped bass, we identified several attractants that dramatically increased consumption of the all-plant diet to levels comparable to fish eating the commercial diet. This research paves the way for significant advancements in developing and testing commercial, least-cost, all-plant diets for hybrid striped bass.
2. Dietary protein can be reduced in tilapia biofloc production. There is a trade-off between feeding for high fish yields vs. water quality deterioration in all aquaculture production systems. This is because fish only convert a portion of the protein in their feed into edible flesh. Feed protein not converted to flesh is excreted as waste that deteriorates water quality in the system and can become toxic to the fish. Biofloc technology production systems, on the other hand, contain not only the fish being grown, but a community of microorganisms suspended in the water —the biofloc—that quickly consume fish waste, thus removing it as a threat to the fish. Also, certain fish like tilapia, may be able to get some of their nutritional needs by eating the biofloc. Researchers at Stuttgart, Arkansas, quantified the relationship between diet formula, particularly diet protein content, and tilapia yield and water quality in an outdoor intensive biofloc system. The test diets were balanced for limiting nutrients using the latest diet formulation theory for fish. Fish were raised to market size on considerably less protein (5% less than stated protein needs) than previously thought while maintaining better water quality and optimum diet nutrient retention in the fish. This diet formulation represents a good trade-off between economic and environmental risks and maximum production potential for intensive tilapia farmers.
3. Female white bass females preferentially incorporate fatty acids from their diet into eggs. The type of feed fed to commercial broodfish prior to the spawning season, as well as the length of time the feed is fed, tremendously influences the quality, composition, and performance of the resulting eggs and newly hatched fish (fry). In particular, the composition of the dietary fat, i.e., the fatty acid (FA) profile, is one of the most influential factors that determine spawning success. White bass females are one half of the parents used to produce commercial hybrid striped bass fingerlings that supply the U.S. grow-out industry. ARS researchers in Stuttgart, Arkansas, evaluated the fatty acid composition of broodfish white bass ova fed one of six commercial diets which varied significantly in FA composition for four and eight weeks prior to sampling. Fatty acid profiles of eggs from brooders fed each of the six diets were significantly altered according to statistical canonical discriminant analysis. There were also some fatty acids that were preferentially, and rather uniformly, stored in the eggs even though there were large variations in the availability of those FA in the diets, particularly n-3 polyunsaturated FA (so called "heart healthy" fatty acids) such as docosahexaenoic acid (DHA;22:6n-3). By formulating broodfish diets using these results, increases in fry survival and performance are expected by providing 1) greater energy stores for developing fry, e.g., monounsaturated fats, as well as 2) building blocks for brain, eye, and nervous system development (e.g., long chain omega 3 polyunsaturated fatty acids).
4. Hybrid striped bass advanced fingerlings produced successfully in biofloc production system. The goal of the ARS "Grand Challenge" is to produce more food in less space. Stocking an advanced, i.e., larger, hybrid striped bass (HSB) fingerling into production ponds improves fish yield and survival, but production of advanced fingerlings has not been optimized. During advanced fingerling production, a certain percentage of the HSB fingerling population gains an early growth advantage and becomes cannibalistic towards conspecifics. These larger, cannibalistic HSB must be sorted from the population before advanced fingerlings can be stocked for grow-out to market size. Biofloc technology production systems can be used as a water quality management tool to increase fish productivity per unit volume of water because the community of microorganisms suspended in the water – the biofloc – quickly consumes the waste excreted by the intensively fed fish. However, HSB had never been grown in the biofloc production system. Researchers at Stuttgart, Arkansas, quantified the relationship between advanced fingerling yield and stocking rate in an outdoor intensive biofloc system. High yields and survivals of advanced HSB fingerlings were obtained at all stocking rates tested; additionally, the proportion in the population at harvest of larger, cannibalistic fingerlings decreased from 40% to 6% as stocking rate increased. This accomplishment demonstrates, for the first time, that advanced HSB fingerlings can be produced in the biofloc production system and paves the way for HSB farmers to intensify production of advanced fingerlings.
5. Striped bass male fertility is correlated to patterns of sperm DNA methylation. Striped bass (Morone saxatilis) spermatozoa are used to fertilize the eggs of white bass (Morone chrysops) to produce the preferred hybrid for the striped bass aquaculture industry. A major constraint in producing hybrid striped bass is suboptimal production efficiency due to differential fertility from both male and female broodfish. Sperm epigenetic modification has been predicted to be associated with fertility, which could switch genes on and off without changing the DNA sequence itself, with DNA methylation one of the most common modification types which could be associated with sub-fertility or infertility in male striped bass. ARS researchers at Stuttgart, Arkansas, with university collaborators, performed DNA methylation analysis of high fertility and low fertility striped bass spermatozoa and discovered 171 differentially methylated regions (DMRs) were correlated to fertility. These DMRs were associated with proteins involved in forming the sperm flagella apparatus in vertebrates and in hormonal signaling and regulation of tissue development, proliferation and differentiation. The results contribute insights into understanding the mechanism of fertility in striped bass, which will provide powerful tools to identify those males with superior fertility to be integrated in the selective improvement program for this important aquaculture species, and using these results producers will improve their fertilization and hatch rates, ultimately improving profit margins.
6. Mapping gut microbial communities during tilapia larvae culture with probiotic. Bacteria in the gut can have a significant impact on animal health and are heavily influenced by the aquaculture environment. Probiotics are beneficial bacteria that have been demonstrated to improve economically-important traits in fish during continuous administration, such as feed value and enhanced immune response; however, the potential for lasting effects of probiotics administered during early fish development is not fully understood. ARS researchers at Stuttgart, Arkansas, and Hagerman, Idaho, and university collaborators examined the composition of gut bacteria during initial life-stages of tilapia cultured in various environments and with the addition of a probiotic. Probiotic was found to be successfully transferred to tilapia gut via water with high relative abundance and could influence microbial communities. Probiotic was not lasting however and did not colonize gut after discontinuation of administration when transferred to culture conditions. This information is useful for our understanding of the early colonization of gut bacteria along with the persistence of specific populations after probiotic treatment in an effort toward more cost-effective administration practices in aquaculture.
7. Winter feeding for bluegill, an emerging food fish. Demand for bluegill has moved beyond sport fishing to an emerging food-fish market for this and other related Centrarchid fish – i.e., bluegill, crappie, and largemouth bass. Little is known about optimum feeding or nutrient requirements of these fish. Fingerling growers lose millions of dollars yearly to a phenomenon called “winter mortality”. ARS researchers at Stuttgart, Arkansas, and university collaborators, evaluated alternate feeding schedules in commercial stocks of bluegill. Monthly, weekly, and twice weekly feeding schedules were evaluated in cold temperature-controlled tanks using fish survival, growth, and whole body fatty acid profiles as markers of fish performance. Feeding frequency did not improve fish performance significantly, but body fat profiles suggest diet composition is a more important factor to optimize for future improvements. This collaborative work has motivated commercial Centrachid growers to rethink feed and feeding practices, and has prompted future research to improve diet formulas, eliminate winter mortality, and enhance production success in this emerging industry.
Review Publications
Cummins, V., Rawles, S.D., Thompson, K.R., Kobayashi, Y., Hager, J., Webster, C.D. 2017. Evaluation of black soldier fly (Hermetia illucens) larvae meal as partial or total replacement of marine fish meal in practical diets for Pacific white shrimp (Litopenaeus vannamei). Aquaculture. 473:337-344.
Farmer, B.D., Beck, B.H., Mitchell, A.J., Rawles, S.D., Straus, D.L. 2016. Dietary copper effects survival of channel catfish challenged with Flavobacterium columnare. Aquaculture Research. 48(4):1751-1758. doi:10.1111/are.13012.
Beck, B.H., Fuller, S.A., Li, C., Green, B.W., Rawles, S.D., Webster, C.D., Peatman, E. 2016. Hepatic transcriptomic and metabolic responses of hybrid striped bass (Morone saxatilis × Morone chrysops) to acute and chronic hypoxic insult. Comparative Biochemistry and Physiology. 18(Part D):1-9.
Giatsis, C., Ramiro-Garcia, J., Abernathy, J.W., Verreth, J., Smidt, H., Sipkema, D., Verdegem, M. 2016. Probiotic legacy on gut microbial assembly in fish larvae. Scientific Reports. 6:33965.
