Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2007
Publication Date: May 16, 2007
Citation: Shelby, R.A., Lim, C.E., Aksoy, M., Welker, T.L., Klesius, P.H. 2007. Effects of yeast subcomponent diet supplements on growth, stress resistance and immune response in Nile tilapia. 32nd Fish and Feed Nutrition Workshop. Auburn University, Auburn, AL. Technical Abstract: Yeast cells contain glucan and mannan subcomponents which have been reported to boost immunity in several fish species. We prepared diets using a commercial feed supplemented with 4 different yeast or yeast subcomponents obtained from commercial sources. These were added at rates recommended by suppliers. Juvenile Nile tilapia (mean weight 6.7 g) were placed in 4 replicate aquaria and fed twice daily to apparent satiation for a period of 4 weeks. Sampling was conducted for serum immune parameters including protein, immunoglobulin, lysozyme and complement. Data were also collected for feed consumption and weight gain. Fish were fed control diet for an additional 2 weeks, after which final serological testing, cortisol response to low water stress, and a disease challenge with Streptococcus iniae were conducted. Betagard (purified beta-glucan) supplemented feed caused an increase in immunoglobulin when compared to those receiving the control diet after 4 weeks. There were no differences in serological parameters after additional 2 weeks of feeding the control diet. Weight gains and feeding efficiency were not different among the diets. Cortisol levels were elevated due to stress, but not related to diet. Ten days following challenge the overall mortality was 36%, with no differences among treatment groups with respect to morbidity or mortality. Specific immunity to S. iniae, measured by ELISA, did not reveal differences in the sera of fish surviving the challenge. We conclude that the incorporation of these products into the diet of Nile tilapia at these rates and for this duration of feeding had a minimal effect on immune function and no effect on growth or mortality following S. iniae challenge.