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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 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: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 13, 2007
Publication Date: May 22, 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. Animal Feed Science And Technology.

Interpretive Summary: 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. It is important to understand how plant components that are present in low levels, yet have an affect on the physiology of the animal, alter fish health and production efficiency. '-glucans are present in barley, and because both the source and level of '-glucans are believed to determine their effect on immune function, a feeding trial was performed to screen 3 barley genotypes containing different levels of '-glucan for their ability to influence growth, and disease resistance of rainbow trout. 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 which consisted 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 of rainbow trout. 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: Concomitant with the higher inclusion levels and variety of plant-based ingredients in aquaculture feeds, 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 for their ability to influence growth, immune function, and disease resistance of rainbow trout. 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. Rainbow trout (approximately 14.3 g initial weight) cultured in 145-L liter fiberglass tanks (50 fish/tank; 3 tank/diet) in a fresh water flow through system were fed the test diets fed by hand to satiation for 9 weeks. 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 of rainbow trout. 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: 11/27/2014
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