Submitted to: Aquaculture America Conference
Publication Type: Abstract only
Publication Acceptance Date: 12/13/2005
Publication Date: 2/3/2006
Citation: Lim, C.E., Aksoy, M., Shelby, R.A., Li, M.H., Klesius, P.H. 2006. Influence of dietary levels of fish oil and vitamin E on growth and resistance of channel catfish to Edwarsiella ictaluri challenge. Aquaculture America Conference. Las Vegas. NV. Interpretive Summary:
Technical Abstract: Dietary lipids are an important source of energy and essential fatty acids that are required for normal growth, development and maintaining health. Channel catfish have a requirement for linolenic acid or eicosaenoic acid and docosaenoic acid. However, fish tissues and diets containing large quantities of these highly unsaturated fatty acids are more susceptible to lipid peroxidation. Vitamin E (a-tocopherol) which is also dietary essential for catfish is known for its role in the prevention of lipid peroxidation. Early studies reported that the requirement of vitamin E in some fish species is affected by dietary levels of polyunsaturated fatty acids. Thus, this study was conducted to determine the effect of increasing dietary levels of fish oil on vitamin E requirement and their effect on growth performance and resistance of channel catfish to Edwardsiella ictaluri challenge. Basal purified diets (32% protein and 2900 kcal DE/kg) supplemented with 6, 10 and 14% menhaden fish oil were each supplemented with 50, 100 and 200 mg vitamin E/kg (3 x 3 factorial experiment) and were fed to juvenile channel catfish in triplicate aquaria for 12 weeks. Weight gain, feed consumption and feed efficiency were not affected by dietary levels of lipid or vitamin E or their interaction. Survival rate at the end of week 12 was significantly lowest for fish fed the diet containing 14% fish oil, regardless of vitamin E content. Whole body moisture significantly decreased and lipid increased when dietary lipid levels were increased to 10%. Increasing dietary lipid to 14% did not further affect body moisture and lipid contents. Dietary vitamin E levels had no effect on body proximate composition. Lipid content of liver was not influenced by dietary fish oil and vitamin E levels or their interaction. Hepatosomatic index was not affected by vitamin E levels but significantly decreased with increasing lipid levels. Liver vitamin E content was significantly affected by dietary levels of fish oil, vitamin E and their interaction. Tissue (liver and whole body) n-3 fatty acids increased whereas n-9 fatty acids decreased with increasing dietary fish oil levels. Neither fish oil nor vitamin E levels and their interaction affected hematological parameters, serum protein, total immunoglobulin, lysozyme activity and antibody titer against E. ictaluri. Natural hemolytic complement activity increased in fish fed the 14% fish oil. High level (200 mg/kg) of vitamin E decreased natural hemolytic complement activity but increased superoxide anion production of leukocytes. However, fish oil at the 10% level was sufficient to stimulate macrophage chemotaxis and phagocytosis. Both lipid and vitamin E levels and their interaction had no effect on the resistance of channel catfish juveniles to E. ictaluri infection.