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United States Department of Agriculture

Agricultural Research Service

Research Project: INTEGRATION OF NUTRITIONAL, GENETIC AND PHYSIOLOGICAL APPROACHES TO IMPROVE PRODUCTION EFFICIENCY OF RAINBOW TROUT

Location: Small Grains and Potato Germplasm Research

Title: Evaluation of the Ability of Barley Genotypes Containing Different Amounts of ¿-Glucan to Alter Growth and Disease Resistance of Rainbow Trout Oncorhynchus Mykiss

Authors
item Sealey, W. - UNIV OF ID, HAGERMAN
item Barrows, Frederic
item Hang, An
item Johansen, K. - FORMER USDA ARS EMPLOYEE
item Overturf, Kenneth
item Lapatra, S. - UNIV OF ID, HAGERMAN
item Hardy, R. - UNIV OF ID, HAGERMAN

Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: November 18, 2006
Publication Date: June 1, 2007
Repository URL: http://riley.nal.usda.gov/nal_web/digi/submission.html
Citation: Sealey, W.M., Barrows, F., Hang, A., Johansen, K.A., Overturf, K.E., Lapatra, S., Hardy, R.W. 2007. Evaluation of the ability of barley genotypes containing different amounts of ¿-glucan to alter growth and disease resistance of rainbow trout oncorhynchus mykiss. Global Aquaculture Advocate.10(3):70-74

Interpretive Summary: As aquaculture strives to maintain profitability and sustainability in an era of escalating competition for fishmeal and fish oil, plant-based feedstuffs are being incorporated into fish feeds at an increasing rate. Along with the higher inclusion levels and increased variety of plant-based ingredients in these feeds, there is a vital need to understand how minor biologically-active plant components alter fish growth and health. Also lacking is information regarding how levels of these bio-active components differ between plant sources. This information is necessary to avoid ingredient substitutions which could reduce fish performance. Three experimental diets were prepared by substituting each of three barley genotypes containing different amounts of '-glucan, 3.8% (low), 5.2% (average) and 8.2% (high) '-glucan barley, respectively, for the entire wheat portion of the diet. An additional test diet, consisting of the control diet supplemented with a commercially available yeast '-glucan product (MacroGard®) at the manufacturer’s recommended level, also was evaluated. Substituting barley flour for wheat flour in a fish-meal based diet did not substantially alter weight gain or proximate composition. In contrast, positive effects of barley genotype on disease resistance were observed. Fish fed the average or high '-glucan barley genotypes had survival similar to those fed the commercially available yeast '-glucan supplemented diet and higher than trout fed the wheat control diet following IHNV challenge. These results indicate that select barley genotypes can be substituted for wheat without significant detrimental effects on production efficiency while potentially increasing resistance to viral pathogens.

Technical Abstract: The composition of trout feeds is changing from high fish-meal levels to high levels of plant-derived ingredients such as corn, soybeans, and barley. There is a pressing need to understand how quantitatively minor, yet biologically-active, plant components such as '-glucans alter fish health and production efficiency. Because both the source and level of '-glucans are believed to determine their immunostimulatory function, a feeding trial was performed to screen 3 barley genotypes containing different levels of '-glucan. Three experimental diets were prepared by substituting each of three barley genotypes containing different amounts of '-glucan, 3.8% (low), 5.2% (average) and 8.2% (high) '-glucan barley, respectively, for the entire wheat portion of the diet. At 3 and 9 weeks post weighing, fish were sampled for determination of respiratory burst activity, and lysozyme and TNF-' expression. At the conclusion of the feeding trial, fish remaining after sampling were pooled by diet; one subsample was examined for their ability to respond humorally to infectious hematopoietic necrosis virus (IHNV) and two other subsamples were challenged by intraperitoneal injection with IHNV. Substituting barley flour for wheat flour in a fish-meal based diet did not substantially alter weight gain or proximate composition. In contrast, positive effects of barley genotype on disease resistance were observed. Fish fed the average or high '-glucan barley genotypes had survival similar to those fed the commercially available yeast '-glucan supplemented diet and higher than trout fed the wheat control diet following IHNV challenge. These results indicate that select barley genotypes can be substituted for wheat without significant detrimental effects on production efficiency while potentially increasing resistance to viral pathogens.

Last Modified: 9/22/2014
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