Gary S. Burr

Baking Reduces Prostaglandin, Resolvin, and Hydroxy-Fatty Acid Content of Farm-Raised Atlantic Salmon (Salmo salar)

The consumption of seafood enriched in n-3 polyunsaturated fatty acids (PUFA) is associated with a decreased risk of cardiovascular disease. Several n-3 oxidation products from eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (22:6n-3) have known protective effects in the vasculature. It is not known whether the consumption of cooked seafood enriched in n-3 PUFA causes appreciable consumption of lipid oxidation products. We tested the hypothesis that baking Atlantic salmon (Salmo salar) increases the level of n-3 and n-6 PUFA oxidation products over raw salmon. We measured the contents of several monohydroxy-fatty acids (MHFA), prostanoids, and resolvins. Our data demonstrate that baking did not change the overall total levels of MHFA. However, baking resulted in selective regioisomeric loss of hydroxy fatty acids from arachidonic acid (20:4n-6) and EPA, while significantly increasing hydroxyl-linoleic acid levels. The contents of prostanoids and resolvins were reduced several-fold with baking. The inclusion of a coating on the salmon prior to baking reduced the loss of some MHFA but had no effect on prostanoid losses incurred by baking. Baking did not decrease n-3 PUFA contents, indicating that baking of salmon is an acceptable means of preparation that does not alter the potential health benefits of high n-3 seafood consumption. The extent to which the levels of MHFA, prostanoids, and resolvins in the raw or baked fish have physiologic consequence for humans needs to be determined.

Dose-Dependent Consumption of Farmed Atlantic Salmon (Salmo salar) Increases Plasma Phospholipid n-3 Fatty Acids Differentially

Enhanced n-3 fatty acid intake benefits cardiovascular disease (CVD) risk reduction. Increasing consumption at a population level may be better addressed by diet than through supplementation. However, limited data are available on the effect of the dose response to fish intake on plasma levels of n-3 fatty acids. To compare the effects of different doses of farmed Atlantic salmon on plasma phospholipid fatty acid proportions and CVD risk biomarkers (eg, glucose, insulin, homeostasis model of assessment-insulin resistance, high-sensitivity C-reactive protein, and interleukin-6) in healthy subjects we performed a randomized three-period crossover-designed trial (4-week treatment, 4- to 8-week washout) to compare the effects of twice per week consumption of farmed Atlantic salmon at doses of 90, 180, and 270 g in 19 apparently healthy men and women (mean age 40 to 65 years) and a body mass index between 25 and 34.9. All study visits were conducted at the US Department of Agriculture Agricultural Research Service Grand Forks Human Nutrition Research Center. Eicosapentaenoic acid and total n-3 concentrations were increased (P<0.05) by all treatments in a dose-response manner, with total n-3 of 8.03% ± 0.26% and 9.21% ± 0.26% for 180- and 270-g doses, respectively. Linoleic acid did not change in response to treatment, whereas arachidonic acid (P<0.05) and total n-6 fatty acids decreased dose dependently (<0.0001). The addition of farmed Atlantic salmon to the diet twice per week for 4 weeks at portions of 180 g and 270 g modifies phospholipid fatty acid proportions of n-3 and n-6 in a level associated with decreased risk for CVD.

A transdisciplinary approach to the initial validation of a single cell protein as an alternative protein source for use in aquafeeds

The human population is growing and, globally, we must meet the challenge of increased protein needs required to feed this population. Single cell proteins (SCP), when coupled to aquaculture production, offer a means to ensure future protein needs can be met without direct competition with food for people. To demonstrate a given type of SCP has potential as a protein source for use in aquaculture feed, a number of steps need to be validated including demonstrating that the SCP is accepted by the species in question, leads to equivalent survival and growth, does not result in illness or other maladies, is palatable to the consumer, is cost effective to produce and can easily be incorporated into diets using existing technology. Here we examine white shrimp (Litopenaeus vannamei) growth and consumer taste preference, smallmouth grunt (Haemulon chrysargyreum) growth, survival, health and gut microbiota, and Atlantic salmon (Salmo salar) digestibility when fed diets that substitute the bacterium Methylobacterium extorquens at a level of 30% (grunts), 100% (shrimp), or 55% (salmon) of the fishmeal in a compound feed. In each of these tests, animals performed equivalently when fed diets containing M. extorquens as when fed a standard aquaculture diet. This transdisciplinary approach is a first validation of this bacterium as a potential SCP protein substitute in aquafeeds. Given the ease to produce this SCP through an aerobic fermentation process, the broad applicability for use in aquaculture indicates the promise of M. extorquens in leading toward greater food security in the future.

Growth of Atlantic Salmon, Salmo salar, Fed Diets Containing Barley Protein Concentrate

A 16-week feeding trial was conducted with juvenile Atlantic salmon (123 g/fish initial weight) to determine the effects of adding either 11% or 22% barley protein concentrate (BPC) to the diet compared to salmon fed a reference diet (0% BPC) containing mostly fishmeal. The fish were stocked into twelve 0.264 m3 tanks, providing 40 fish per tank with an average density of 18.55 kg/m3. Temperature was maintained at ˜12°C and salinity at ˜2 ppt using ground water during the study. There were no significant differences in specific growth rate (0.62 basal, 0.60 11% BPC, 0.72 22% BPC), feed conversion (1.06, 1.37, 1.09), weight gain (124.3 g, 113.5 g, 155.3 g), proximate composition of the salmon for lipid (8.4%, 7.8%, 9.8%), protein (17.3%, 17.1%, 18.6%), moisture (71.4%, 72.3%, 69.4%), and ash (6.5%, 6.1%, 6.9%) among any of the treatment groups. Salmon fed the diet containing 22% barley protein concentrate, however, had significantly greater energy retention (34%) compared to the fish fed the other diets (23%–28%). The results of this study indicate that barley protein concentrate is an acceptable feed ingredient for Atlantic salmon that should provide performance similar to fishmeal at inclusion rates below 22%.

Characteristics and Modification of the Intestinal Tract Microbiota of the Channel Catfish Ictalurus punctatus

Catfish is the leading commercial aquaculture enterprise in the United States, and many of the issues that have been important for other mass-produced food animals have become areas of research focus for potential improvement in the growth performance and health of catfish. A critical component that can influence both the health and nutrition of catfish is the intestinal tract. The intestinal tract, in addition to being the point of origin for digestion and absorption of nutrients derived from consumed diets, harbors an indigenous microflora that can interact with the host. The composition and role of the intestinal microbial communities in fishes remain poorly understood. To understand the effects of the entire microbial community on the host, additional studies and improved isolation methods are recommended. Along with the lack of knowledge about the composition of the community, little is known about the role of these microorganisms in the intestinal tract. An increased understanding of the intestinal microflora in catfish has potential for manipulation or alteration to improve disease resistance and growth performance, allowing the channel catfish to consume diets made with less expensive ingredients, such as crop residues, already fairly cheap. Recent aquaculture feed trials using prebiotics and probiotics report enhanced physiological and immune responses that contribute to improvements in aquaculture health. These trials are reviewed.