This study aims to improve water quality and reduce eutrophication downstream when receiving water from aquaculture facilities that can support the aquaculture industry and increase fish production capacity. The primary objective is to investigate a novel approach, using magnesium (Mg)-modified biochar water treatment systems from pinewood, to remove the main eutrophication agents (i.e., phosphorous and nitrogen) from the effluents of aquaculture facilities in Magic Valley, Idaho. The downstream water contains approximately 0.14 mg/L of phosphorous and 2.25 mg/L of nitrogen. The results show that the initial P2O5 concentration between Mg-modified and non-modified biochar is comparable. After exposure to aquaculture production water, the modified biochar is shown to have a significant increase in phosphorous and nitrogen adsorption. Non-modified biochar started with noticeably higher concentration levels of nitrogen than modified biochar. Over time in the treatment water, the modified biochar showed a significant increase in nitrogen concentration. Mg bonded to the modified biochar is shown to decrease drastically after exposure to the effluent. This could be due to the insufficient bonding of the magnesium to biomass feedstocks during pre-processing and biochar production. The amount of biochar near the end of experimentation is almost comparable to the non-modified char. We concluded that the proposed approach, using a Mg-modified biochar water treatment system, could sequester more nitrogen and phosphorous over time.

We hypothesized that a low phytosterol oil, such as soybean oil, in combination with an a-linolenic acid (ALA) rich oil, such as linseed oil, and supplemental cholesterol could effectively replace fish oil in salmonid feeds. As such, the primary objective was to blend soybean oil with linseed oil and supplemental cholesterol to maintain fish growth and increase de novo production of the omega-3 fatty acids (n-3 FA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in trout muscle, since EPA and DHA have been identified as beneficial nutrients in human nutrition, and farmed seafood must meet consumer needs and expectations. To accomplish this, we used soy oil for its low phytosterol properties in combination with linseed oil for its n-3 FA content, with and without cholesterol to improve utilization. Upon conclusion of the study, our results did not support our hypothesis. Trout fed plant-based diets containing any amount of soy oil had reduced growth performance. Only fish fed the plant-based diet with 100% linseed oil plus supplemental cholesterol grew as well as both control groups, fishmeal/fish oil and plant meal/fish oil. Dietary cholesterol supplementation increased plasma cholesterol levels and EPA in fillets (P < 0.05). Two-way ANOVA demonstrated that growth performance and muscle EPA content were significantly increased in fish fed cholesterol-supplemented diets. However, expression of genes involved in fatty acid biosynthesis were not enhanced by cholesterol, suggesting a potential disconnect between gene expression and functional activity. Although our hypothesis failed and soybean oil was found to be less accepted by the fish, resulting in lower growth and feed intake, we were successful in developing a high soy-protein diet (35%) with all-plant ingredients using linseed oil and supplemental cholesterol that resulted in equal fish performance to fish fed a fishmeal/fish oil control diet. More research is needed to identify a cost-effective EPA/DHA source to meet consumer needs and expectations for n-3 FA in trout fillets.

This study aims to construct a novel and sustainable approach for remediating aquaculture-generated water contamination using various engineered biochars. Particularly, this study focuses on capturing nitrogen and phosphorus from downstream water of commercial fish farms in Magic Valley, Idaho, containing approximately 2.26 mg/L of nitrogen and 0.15 mg/L of phosphorous. The results indicate that the proposed approach can improve downstream waters by adsorbing micronutrients (e.g., nitrogen-ammonia, nitrate-n + nitrite-n, and total phosphorus). Water treatment time and biochar pH are two key parameters strongly associated with adsorbed compounds. Molecular-level characterization of solvent-extracted organics from biochar materials (before and after water treatment) suggests increased levels of highly oxygenated molecules as a function of increasing water treatment time. Also, the results show the enrichment in organic species with higher molecular weight and increased double bond equivalents, with a compositional range similar to that of dissolved organic matter. Upon water treatment, extracted organics revealed higher abundances of compounds with higher H/C and O/C ratios. The engineered biochars, after water treatment, can be reused as nutrient-rich fertilizers. This study concluded that the engineered biochars could sequester more nitrogen and phosphorous over time. Also, the proposed approach can simultaneously increase fish production capacity and support the aquaculture industry in different regions by improving water quality and enabling aquaculture expansion.

The United States (U.S.) has a nearly USD 17 billion seafood trade deficit annually. However, the U.S. aquaculture industry faces strict micronutrient (e.g., phosphorus and nitrogen) level mandates that negatively impact fish production, especially for the state of Idaho, which produces 70–75% of the nation’s rainbow trout. This study investigates the sustainability benefits of producing engineered biomaterials from lignocellulosic-based feedstocks near collection sites via portable biorefineries for use by fish farms to reduce eutrophication (oversupply of micronutrients) impacts. In this study, sustainability assessments are performed on a case study in southern Idaho, the largest U.S. commercial producer of rainbow trout. The results show that 20 and 60 min of water treatment, using small particle size biomaterial from lodgepole pine, has the highest total phosphorus removal rate, at 150–180 g of phosphorus per 1 metric ton of engineered biomaterials. The results of techno-economic and environmental impacts studies indicate that pinewood-based biomaterials production cost ranges from USD 213 USD 242 per ton and reduces the eutrophication potential by 5–17 kg PO4eq/ton. Additionally, the environmental impact results show that the total greenhouse gas emission for biomaterial production is 47–54 kg CO2eq/ton; however, the used biomaterials after water treatment can be sold for around USD 850 per ton as nutrient-rich soil conditioners. This study concluded that engineered biomaterials from lignocellulosic-based feedstocks could be a sustainable solution to the challenge that aquaculture faces, particularly capturing micronutrients from eutrophic water and reusing them as fertilizers.

The aim of this study was to evaluate the effects of Latitude™ oil (transgenic canola) fed to rainbow trout, Oncorhynchus mykiss , for 52 weeks on growth performance, non-specific immune responses, histology, and filet omega-3 fatty acid content. Latitude™ oil (LO) has high lipid digestibility (93%), and contains omega-3 fatty acids eicosapentaenoic acid (EPA, C20:5n-3), docosapentaenoic acid (DPA, C22:5n-3), and docosahexaenoic acid (DHA, C22:6n-3). Three isonitrogenous (49%), isolipidic (20%) and isocaloric (24.2 MJ kg −1 ) diets differing by lipid source (0, 8, or 16% LO, replacing fish oil and poultry fat) were fed over an entire production cycle beginning with 19 g juvenile fish. At the end of the 52-week feeding trial, final body weight, weight gain and specific growth rate of fish fed 8% LO (LO-8) and 16% LO (LO-16) diets were significantly higher than those fed the 0% LO (LO-0) diet ( P < 0.05). Phagocytic respiratory burst in fish fed the LO-16 diet was significantly higher than those fish fed the other 2 diets ( P < 0.05). There were no differences in superoxide dismutase, catalase and lysozyme. Histological examination of the distal intestine indicated reduced inflammation in fish fed the LO-8 diet but not the LO-0 and LO-16 diets. Filet DHA content of fish fed the LO-8 and LO-16 diets were similar to those of fish fed the LO-0 diet. As these diets had lower DHA content, this suggests dietary EPA and DPA from LO was converted to DHA and deposited in the filet. This is supported by increased expression of genes involved in fatty acid elongation, desaturation and beta oxidation in both liver and muscle of fish fed LO ( P < 0.05). Total EPA+DHA content of the edible filet ranged between 1,079–1,241 mg 100 g −1 across treatments, each providing the recommended daily intake for human consumption (500–1,000 mg day −1 ). Overall, this study demonstrated that LO fed over an entire production period is a highly digestible lipid source suitable and sustainable for meeting the fatty acid requirements of rainbow trout, as well as consumer expectations for filet omega-3 fatty acid content.

A strain of rainbow trout at the Hagerman Fish Culture Experiment Station has undergone a long-term selection program for growth on a plant-based diet (HGM strain). Comparing fish from the F-8 generation to a commonly available commercial strain selected for growth (CSS), we sought to investigate potential differences in oral tolerance, intestinal microbiota richness and overall growth when fed a 40% SBM diet. Triplicate tanks (initial mean fish weight 77.9 +/- 1.1 g) of each strain were fed diets containing either 0% or 40% SBM over 12 weeks in a factorial design. Fish were weighed every four weeks and subsampled to assess gene expression in the distal intestine. Fish were also sampled at the beginning and end of the study to assess gut histology and characterize intestinal microbiota. At twelve weeks, the HGM strain showed superior growth on both diets (p < .001). Gene expression related to gut health and inflammation show reduced inflammatory response in the HGM fish compared to the CSS strain. Significant effects of strain and diet were also observed on metrics of gut microbiota diversity. Together, these results suggest selection for growth on a plant-based diet also drives selection for increased oral tolerance for dietary soybean meal inclusion.

The effects of graded levels (0–20% total dietary inclusion) of commercial, solvent-extracted soybean meal (SBM) and expeller sunflower meal (SFM) were investigated on growth, nutrient utilization, and pro-inflammatory gene expression in the distal intestine and spleen of two commercial Canadian strains (Strain 1 and Strain 2) of Arctic charr. Five experimental diets with increasing inclusion of SBM or SFM were fed for 84days to two Canadian strains of Arctic charr (initial body weight=9g/fish). Feeding these diets resulted in no differences in growth rate (measured as final weight or thermal-unit growth coefficient, TGC) in the two strains. Increased inclusion level of plant proteins negatively affected FE (P<0.0001) with effects most commonly observed in groups fed SBM-based diets. The effect of the ingredient was significant (P<0.05) on PXR gene expression in the distal intestine; PXR expression was higher with SBM than with SFM. The effect of the inclusion level of plant ingredients was significant (P<0.05) on IL-Iβ gene expression in the spleen. Feed intake, FE, NRE, ERE, whole body crude protein, lipid, gross energy, and organo-somatic indices were significantly (P<0.05) affected by genetic strain examined. Strain 2 exhibited higher FE and carcass crude protein content and lower carcass lipid content. The difference in FE, protein and lipid content for the 2 genetic strains of charr may indicate variations in efficiency for protein and lipid utilization, with a potential protein-sparing effect of dietary lipid noted in Strain 2.

Inclusion rates of soybean meal in salmonid diets are currently kept low to minimize detrimental effects on growth, enteritis and immune responses. Probiotics have been used to treat both infectious and noninfectious enteritis in humans and other terrestrial animals and may represent a feasible method for increasing soy utilization in soy-sensitive aquatic species. To test the hypothesis that probiotics incorporation in rainbow trout starter diets can induce immune-mediated soybean tolerance, a two-phase experimental design was employed. In the starter phase (first feeding, 0.13 +/- 0.01 to 6.5 +/- 0.32 g fish(-1)), a practical-type diet was formulated to contain 48% crude protein and 20% crude fat containing either 0 (S0), 10 (S10) or 20% (S20) soybean meal (SBM) and supplemented with (S0P, S10P, S20P) or without a commercially available probiotic (Mycolactor Dry Probiotic (R)) in a 3 x 2 factorial design. Diets were fed to four replicate tanks of fish per treatment (300 fish tank(-1); House Creek strain) for E weeks. Trout were reared in 150 L tanks supplied with 4 L min(-1) of constant temperature (14.8 degrees C) flow-through spring water. Potentially soy tolerant rainbow trout produced by feeding probiotics and increased levels of soybean meal in starter diets as described above were then fed the industry standard level 15% (G15) or a diet with a challenge level of 43% (G43) of soybean meal during a 12 week grow-out and digestibility trial. Pathological changes were observed in intestines of fish fed the 43% SBM during grow-out; however, these changes were less severe when fish had been exposed to soybean meal in starter diets. The addition of probiotics to starter diets appeared to improve soybean meal utilization by first feeding rainbow trout, but probiotic use had only limited benefits when they were not continuously provided in the diet. (C) 2009 Elsevier B.V. All rights reserved.

We evaluated the ability of partially autolyzed yeast and Grobiotic-A to improve immune response and disease resistance in rainbow trout Oncorhynchus mykiss. Experimental diets were prepared by adding partially autolyzed yeast or Grobiotic-A to a practical trout diet at the manufacturer-recommended level of 2%; the control was the same diet without supplementation. Rainbow trout (initial weight = approximately 14.3 g) were cultured in 145-L fiberglass tanks (50 fish/tank; 3 tanks/diet) in a freshwater flow through system. Fish were hand-fed the diets to apparent satiation 3 times/d, 6 d/week for 9 weeks. At 3 and 9 weeks postweighing, fish were sampled to determine respiratory burst activity, plasma protein, total immunoglobulin and lysozyme, and tumor necrosis factor-alpha (TNF-alpha) expression. At the conclusion of the feeding trial (9 weeks), fish remaining after sampling were pooled by diet; one subsample was examined for the ability to respond humorally to infectious hematopoietic necrosis virus (IHNV), and another subsample was challenged by intraperitoneal injection with IHNV. Dietary inclusion of 2% partially autolyzed yeast or Grobiotic-A had no negative impacts on health or growth of rainbow trout. In contrast, although substantial variability was observed for immune response variables, use of 2% partially autolyzed yeast or Grobiotic-A produced striking improvements in survival of rainbow trout after experimental challenge with IHNV.

Continued growth and intensification of aquaculture production depends upon the development of sustainable protein sources to replace fish meal in aquafeeds. This document reviews various plant feedstuffs, which currently are or potentially may be incorporated into aquafeeds to support the sustainable production of various fish species in aquaculture. The plant feedstuffs considered include oilseeds, legumes and cereal grains, which traditionally have been used as protein or energy concentrates as well as novel products developed through various processing technologies. The nutritional composition of these various feedstuffs are considered along with the presence of any bioactive compounds that may positively or negatively affect the target organism. Lipid composition of these feedstuffs is not specifically considered although it is recognized that incorporating lipid supplements in aquafeeds to achieve proper fatty acid profiles to meet the metabolic requirements of fish and maximize human health benefits are important aspects. Specific strategies and techniques to optimize the nutritional composition of plant feedstuffs and limit potentially adverse effects of bioactive compounds are also described. Such information will provide a foundation for developing strategic research plans for increasing the use of plant feedstuffs in aquaculture to reduce dependence of animal feedstuffs and thereby enhance the sustainability of aquaculture.