SBIR-STTR Award

The term winter kill refers to a serious disease problem affecting pond-reared channel catfish during the late fall, winter, and early spring. Fish loses can be high and all sizes of fish can be affected. The cause and pathogene 'is of winter kill is largely unknown. It is believed that it is caused by some predisposing condition that decreases the ability of the fish to adapt to stress associated with cold. Nutritional status appears to be a factor. We propose to evaluate the effects by feeding high levels of Vitamin C, Vitamin E, protein, or omega-3 fatty acids, either individually or in combination, to catfish reared in earthen ponds during the winter. We also propose to wloadZ the fish with these critical nutrients prior to onset of winter. The fish will be stressed prior to stocking in order to accentuate the disease process. The fish will be fed on a typical winter feeding schedule from late September until late March. Monthly samples of various tissues will be taken for nutrient analysis. Treatment effects will be evaluated by nutrient storage, histological examination, weight gain, serum electrolytes, and incidence and severity of winter kill.Applications:Information needed to develop catfish feeds and feeding methods to help alleviate winter kill and perhaps other diseases of catfish that occur primarily as the result of stress will be generated. Catfish producers will be the primary benefactors.

Winter kill refers to a serious disease problem affecting pond-raised catfish. Recent research indicated that winter kill is an immunodeficiency disease triggered by onset of low temperatures and that the fungus involved, Saprolegnia sp, may be a true pathogen/parasite and not simply a saprophyte. If the fungus is a primary invader, controlling it offers a means of preventing or treating winter kill. An alternative means of controlling the disease may be to counteract the immunosuppression using nutritional supplements. We have been unable to control winter kill through nutrition; however, dietary menhaden fish oil appeared to increase the severity of the disease. In our proposed study, we will evaluate the use of copper sulfate, potassium permanganate, formalin, and salt to prevent or treat winter kill in catfish. Initially studies will be conducted with channel catfish under controlled conditions in the laboratory to determine efficacy of the chemicals and to established a treatment rate. Studies will then be conducted in earthen ponds to established efficacy of chemical treatment under practical conditions. The effect of dietary fat on winter kill will also be evaluated.

Anticipated Results:
If the proposed studies are successful, the results would offer an effective and economical method to prevent the occurrence of winter kill or allow treatment of outbreaks of the disease. The chemicals under test are commonly used in the catfish industry; thus, their use in commercial catfish culture for alleviating winter kill would be acceptable. Also, the results of the study on dietary fat should provide evidence concerning the suitability of menhaden fish oil for use in catfish feeds. Menhaden fish oil is commonly used in catfish feeds, particularly during winter months.