EVALUATION OF THE ABILITY OF BARLEY VARIETIES CONTAINING DIFFERENT AMOUNTS OF B-GLUCAN TO ALTER GROWTH, IMMUNE FUNCTION, AND DISEASE RESISTANCE OF RAINBOW TROUT ONCORHYNCHUS MYKISS.

Authors: SEALEY, WENDY - UNIVERSITY OF IDAHO; Barrows, Frederic; Hang, An; Johansen, Katherine; Overturf, Kenneth - Ken; LAPATRA, SCOTT - CLEAR SPRINGS FOODS; HARDY, RONALD - UNIVERSITY OF IDAHO

Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: 9/1/2005
Publication Date: 2/13/2006
Citation: Sealey, W.M., Barrows, F., Hang, A., Johansen, K.A., Overturf, K.E., Lapatra, S., Hardy, R.W. 2006. Evaluation of the ability of barley varieties containing different amounts of b-glucan to alter growth, immune function, and disease resistance of rainbow trout oncorhynchus mykiss.. Book of Abstracts Aquaculture America.

Interpretive Summary: '-glucans are a structural component of some organisms and have been shown to improve the immune response of fish. An experiment was conducted to compare the effect of feeding high beta glucan varieties of barley to beta-glucans derived from other sources, including commercial products. Fish fed diets containing the average or high '-glucan containing barley varieties had survival similar to those fed the Macrogard® diet and significantly better than trout fed the wheat control diet following IHNV challenge. These results indicate that barley can be substituted for wheat without significant detrimental effects on production efficiency while potentially increasing resistance to viral pathogens

Technical Abstract: '-glucans are structural components of the cell wall of bacteria, fungi, yeast and some plants. In contrast to '-glucans from fungi and yeast which contain ' 1,6 and ' 1,3 linkages, '-glucans from plants such as barley, oats, rye and wheat primarily consist of mixed ' 1,3 and ' 1,4 linkages at levels of 6, 5, 2, and less than 1%, respectively. However, within plant species, '-glucan composition can vary substantially based on growing conditions as well as variety. Because both the structure and level of '-glucans are believed to determine immunostimulatory function, a feeding trial was performed to screen 3 different barley varieties for their ability to alter growth, immune function, and disease resistance of rainbow trout when barley was substituted for the wheat portion of a practical-type diet. A practical-type control diet that met or exceeded all the known dietary requirements of rainbow trout was formulated with approximately half of the protein from fish meal and half from plant sources with wheat flour as the carbohydrate source. Three experimental diets were prepared by substituting each of three barley varieties 3.8% (low), 5.2% (average) and 8.2% (high) '-glucan barley 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. Rainbow trout (House Creek strain, College of Southern Idaho; approximately 20 g initial weight) cultured in 145-L liter fiberglass tanks (50 fish/tank; 3 tank/diet) in a fresh water flow through system (spring water, 14.5ºC at 4L/min) were fed the test diets fed by hand to satiation for 9 weeks. At 3 and 9 weeks post weighing, 9 fish/tank were sampled for determination of plasma total protein and antibody levels, respiratory burst activity, lysozyme and TNF-' expression. At the conclusion of the feeding trial, fish remaining after sampling were challenged by intraperitoneal injection with infectious haemopoeitic necrosis virus (IHNV) and mortality was monitored for 14 days. Substituting barley for the wheat portion of a practical-type diet did not substantially alter growth efficiency, weight gain, or tissue proximate composition of rainbow trout. In contrast, some positive effects of barley variety on immune function and disease resistance were observed. Fish fed diets containing the average or high '-glucan containing barley varieties had survival similar to those fed the Macrogard® diet and significantly better than trout fed the wheat control diet following IHNV challenge. These results indicate that barley can be substituted for wheat without significant detrimental effects on production efficiency while potentially increasing resistance to viral pathogens.