Location: Harry K. Dupree Stuttgart National Aquaculture Research Cntr
2018 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 (WB).
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
ARS researchers at Stuttgart, Arkansas, began a study in ponds to assess hybrid striped bass performance when fed a fish meal-free test diet (containing a mix of animal and plant proteins), as well as an all-plant protein test diet containing no animal products. As control diets for comparison, we also will feed a commercial hybrid striped bass diet currently used in the industry, as well as a diet similar in composition to the two test diets but containing some fish meal. Additionally, we are investigating whether phytase (an enzyme that releases phosphorus bound up in plant proteins) can eliminate the need for phosphorus supplementation of fish diets. This study is the culmination of several projects to maximize replacement of fish meal in hybrid striped bass diets by validating diets in pond production. (Objective 1)
Significant progress was made in a subordinate project to replace fish meal in hybrid striped bass diets with newly developed protein blends. Using digestibility coefficients determined during phase I of this project, test diets in which fish meal was replaced with each of the protein blends and supplemented with limiting amino acids were extruded by our cooperator at the U.S. Fish & Wildlife Service Bozeman Feed Technology Lab, Bozeman, Montana. Juvenile hybrid striped bass were stocked into tanks in June for the feeding trial, which serves as the Master’s thesis project for a graduate student at the University of Arkansas at Pine Bluff, Pine Bluff, Arkansas. (Objective 1)
Significant progress was made on a cooperative project in collaboration with researchers at the University of Arkansas at Pine Bluff, Pine Bluff, Arkansas, and the U.S. Fish & Wildlife Service Bozeman Feed Technology Lab, Bozeman, Montana, to develop alternative, cost-effective ingredients for Nile tilapia diets. Using digestibility coefficients for newly developed protein blends determined in Nile tilapia, test diets were formulated substituting each of the newly developed protein blends for soybean meal. A feeding trial currently is ongoing. (Objective 1)
A feeding trial was conducted to evaluate growth, body composition, and gene regulation in white bass fed diets containing various percentages of fish meal. Animal and plant ingredients, which are environmentally responsible and sustainably produced, were used as alternatives to marine fish meal, which is the most expensive macro-ingredient included in a commercial fish feed. Growth parameters were measured when the study ended, and samples and data are currently being analyzed. (Objective 1)
Phosphorus is present in plant feedstuffs as phytate, which is not available to fish because they cannot digest it. Phytase is an enzyme that releases the phosphorus from the phytate. Reduction of phytate as an anti-nutrient, particularly in the context of iron-sequestration has not yet been considered in catfish or other plant protein-laden aquafeeds. We initiated a study in nylon floating cages to determine if amending a commercially-available catfish diet with different doses of a second-generation phytase affects growth, body composition, hematological parameters, and immune function in channel catfish. This study is continuing through the summer. (Objective 1)
Produced 98 wild and domestic single parent white bass experimental crosses to characterize production traits of interest for the creation of a new synthetic line. Additionally, we developed and implemented a method to further spawn white bass in the offseason (fall) to evaluate additional performance traits, including disease-resistance and tolerance to diet reformulations. Conditioning white bass for fall spawning is ongoing. (Objective 2)
Genetic markers are critical for evaluating population diversity, detecting inbreeding, differentiating unknown individuals by population origin, and, ultimately, selecting for performance traits. In a subordinate project, ARS researchers at Stuttgart, Arkansas, working with researchers from Auburn University, Alabama, examined genetic relationships between a domestic white bass line and five wild populations collected from drainages in Arkansas, Texas, and Alabama. A cost-effective genotyping-by-sequencing (GBS) method was carried out for in-depth genetic analysis, generating 13,872 genome-wide single nucleotide polymorphism (SNP) loci represented across six populations. Stringent filtering of SNP-calling parameters indicated 426 highly informative SNP loci. Population genetic and structure analyses using these loci revealed moderate genetic differentiation between domestic and wild populations (Fst > 0.086), but six clear population clusters. A final set of 57 SNPs was selected for assay design and validation using 96 additional samples. The developed SNP panels could clearly discriminate between domestic stocks and wild-sourced individuals. This study demonstrated the utility of GBS techniques for SNP discovery and the relatively small number of SNPs needed for inference of population structure in white bass. The SNP resources developed in this study will facilitate breeding, genetic tagging, and future selection activities in white bass. (Objective 2)
To advance genetic improvement in white bass, ARS researchers at Stuttgart, Arkansas, evaluated growth performance in domestic and wild strains of white bass under two separate rearing and feeding regimes. In the first study, juvenile white bass growth was evaluated in a tank study where fish were fed to satiation. Wild white bass originating from the Neches River in North Texas were heavier and longer than Stuttgart domestic white bass, with the other wild strains being lighter and shorter than the Stuttgart domestics. In the second study, juvenile white bass were grown in a communal tank and fed a set feed ration. Wild white bass originating from the Neches River in North Texas and the Nueces River in South Texas were significantly heavier than Stuttgart domestic white bass. This is critical to compare the performance of these domestic fish to wild stocks for assessing the impact of selection on important production traits and for the establishment of a new synthetic line of white bass that can reduce the industry’s reliance on wild-sourced broodfish. (Objective 2)
Significant progress was made on a subordinate project in which ARS researchers at Stuttgart, Arkansas, in collaboration with researchers at North Carolina State University, Raleigh, North Carolina, are completing the white bass and striped bass genome sequences. (Objective 2)
Preliminary results of a series of studies in which ARS researchers at Stuttgart, Arkansas, in collaboration with scientists at the University of Arkansas at Pine Bluff, Pine Bluff, Arkansas, and a commercial hybrid striped bass fingerling producer, indicate that cold-shock treatment of hybrid striped bass egg clutches yielded populations of predominantly triploid fish whereas heat-shock treatment did not. Growth characteristics of triploid hybrid striped bass, which are sterile, will be evaluated in the future against diploid hybrid striped bass. (Objective 2)
ARS researchers at Stuttgart, Arkansas, are investigating the effects of diet and the biofloc technology production system on the gut microbiome and the correlation of environmental bacteria and fungus with production traits in tilapia. There has been successful preparation of nearly 1,000 samples for gene sequencing isolated throughout the production cycle. (Objective 3)
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. Completed a follow-up experiment to quantify the relationship between fingerling tilapia growth and yield, and stocking rate in the outdoor BFT production system. Data analyses are in progress and results from this and a previous study should demonstrate the optimal stocking rate to produce an advanced fingerling. (Objective 3)
Fish feed typically is supplemented with inorganic phosphorus 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 a biofloc technology (BFT) production system because of the high quantities of feed fed daily to fish. Completed 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. Fish were fed one of three test diets: the positive control diet, which gave the best results in our 2016 tilapia BFT experiment, contained supplemental inorganic phosphorus to meet the tilapia dietary requirement of available phosphorus; the negative control diet, which was the positive control diet without supplemental inorganic phosphorus; and, the phytase diet, which was the negative control diet supplemented with phytase. Sample and data analyses are on-going. (Objectives 1 and 3)
Accomplishments
1. Heritability of growth in hybrid striped bass correlated liver gene expression. Improved growth rate is a highly desirable trait in aquaculture, but growth of hybrid striped bass can vary greatly throughout the production cycle. In a long-term growth study, ARS researchers at Stuttgart, Arkansas, found that hybrid striped bass growth is a heritable trait and thus, likely can be increased through improved genetics. Between the slowest and fastest growing fish, we further identified differentially expressed genes, several of which were correlated with growth hormone and energy expenditure. A first-generation liver gene expression database was released to the public as well as correlation data to further support a growth selection program. The correlation of growth with key energy expenditure genes will enable breeders to develop predictive markers for use in current breeding programs to include only the top performing individuals in each generation. The development and implementation of these markers is ongoing with University and Industry partners.
2. Phytase enzyme substitutes for inorganic phosphorus in diet for tilapia biofloc production. Fish feed typically is supplemented with inorganic phosphorus 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 biofloc technology production system because of the high quantities of feed fed daily to fish. In a study conducted in an outdoor biofloc production system to investigate the impact of dietary inclusion of phytase on phosphorus retention by tilapia and on water quality, ARS researchers at Stuttgart, Arkansas, found that phytase enzyme can substitute completely for inorganic phosphorus in the fish feed without affecting tilapia growth negatively. Additionally, phosphorus excretion by tilapia was reduced by about 50%, resulting in improved water quality. Reducing potential phosphorus excretion will help fish farmers meet National Pollutant Discharge Elimination System permit requirements.
3. Intensive production of stocker size tilapia in the biofloc production system. Market-size fish can be harvested from grow out ponds sooner if larger, advanced fingerlings, or stockers, are stocked. However, optimization of the overall production cycle requires that stockers also be produced efficiently. Stocking rate is one factor that effects fish growth and can be manipulated to obtain stocker size fish. Much greater numbers of fish are stocked in the biofloc technology production system because the fish live within a community of microorganisms in the water – the biofloc – that consume fish waste quickly, removing it as a threat to the fish. ARS researchers at Stuttgart, Arkansas, quantified the relationship between tilapia stocking rate and growth and yield of stocker-size fish in an outdoor biofloc production system. Yield of stocker-size tilapia increased linearly with stocking rate, whereas mean individual weight decreased linearly. However, stocker-size fish were produced at all stocking rates. Using these relationships farmers can optimize annual production of stocker-size tilapia by manipulating stocking rate and production cycle length.
Review Publications
Fuller, S.A., Rawles, S.D., McEntire, M.E., Bader, T.J., Riche, M.A., Beck, B.H., Webster, C.D. 2017. White bass (Morone chrysops) preferentially retain n-3 PUFA in ova when fed prepared diets with varying FA content. Lipids. 52:823-836.
Woods, L., Li, Y., Ding, Y., Liu, J., Reading, B.J., Fuller, S.A., Song, J. 2018. DNA methylation profiles correlated to striped bass sperm fertility. BMC Genomics. 19:244.
Fuller, S.A., Beck, B.H., McEntire, M.E., Peatman, E., Abernathy, J.W. 2018. Heritability of growth traits and correlation with hepatic gene expression among hybrid striped bass exhibiting extremes in performance. Cogent Biology. 4:1453319.
Green, B.W., Rawles, S.D., Webster, C.D., Mcentire, M.E. 2017. Effect of stocking rate on growing juvenile sunshine bass (Morone chrysops x M. saxatilis) in an outdoor biofloc production system. Journal of the World Aquaculture Society. https://doi:10.1111/jwas.12491.
Rawles, S.D., Green, B.W., McEntire, M.E., Gaylord, T., Barrows, F. 2018. Reducing dietary protein in pond production of hybrid striped bass (Morone chrysops x M. saxatilis): Effects on fish performance and water quality dynamics. Aquaculture. 490:217-227.
Roy, L.A., Rawles, S.D., Kelly, A.M., Webster, C.D., Stone, N., Haukenes, A. 2017. Effect of winter feeding frequency on growth, survival, and fatty acid metabolism of juvenile bluegill (Lepomis macrochirus) and hybrid bluegill (L.cyanellus ×L. macrochirus). Aquaculture. 479:780-789.
Hager, J.V., Rawles, S.D., Xiong, Y.L., Newman, M.C., Webster, C.D. 2018. Edible corn-zein-based coating incorporated with nisin or lemongrass essential oil inhibits Listeria monocytogenes on cultured hybrid striped bass, Morone chrysops x Morone saxatilis, fillets during refrigerated and frozen storage. Journal of the World Aquaculture Society. 50(1):204-218. https://doi.org/10.1111/jwas.12523.
Welker, T.L., Overturf, K.E., Snyder, S., Liu, K., Abernathy, J.W., Frost, J.B., Barrows, F. 2018. Effects of feed processing method (extrusion and expansion-compression pelleting) on water quality and growth of rainbow trout in a commercial setting. Journal of Applied Aquaculture. 30(2):97-124. https://doi.org/10.1080/10454438.2018.1433095.
Welker, T.L., Overturf, K.E., Abernathy, J.W. 2018. Effect of water source and trout strain on expression of stress-affected genes in a commercial setting. North American Journal of Aquaculture. 80(3):249-262. https://doi.org/10.1002/naaq.10028.
