|Li, Menghe - AUBURN UNIVERSITY|
Submitted to: Annual Meeting World Aquaculture Society
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 2007
Publication Date: February 9, 2008
Citation: Lim, C.E., Aksoy, M., Li, M., Welker, T.L., Klesius, P.H. 2008. Influence of Dietary Levels of Lipid and Vitamin E on Growth and Resistance of Nile Tilapia to Streptococcus iniae Challenge [abstract]. World Aquaculture Society. p. 210. Technical Abstract: Dietary lipids are an important source of highly digestible energy and are the only source of essential fatty acids required by fish for normal growth, development and maintaining health. Nile tilapia have been shown to have a requirement for linoleic series fatty acids. Linolenic series fatty acids may also be dietary essential for this species because fish fed diets containing soybean oil rich in both linoleic and linolenic acids provided good growth and reproductive performance. Vitamin E (a-tocopherol) which is also dietary essential for tilapia is known for its function as a biological antioxidant, thus plays an important role in fish immune system function. Early studies reported that the dietary requirement of tilapia for vitamin E increased with increasing levels of dietary lipid. Therefore, this study was conducted to determine the effect of increasing dietary levels of lipid on vitamin E requirement and their effect on growth performance and resistance of Nile tilapia to Streptococcus iniae challenge. Basal purified diets (35% protein and 3.4 kcal DE/g) supplemented with 6, 10 and 14% of 1:1 mixture of corn oil and menhaden fish oil were each supplemented with 50, 100 and 200 mg vitamin E/kg (3 x 3 factorial experiment) and fed to Nile tilapia in triplicate aquaria for 12 weeks. Weight gain, feed intake and survival were not affected by dietary levels of lipid, vitamin E or their interaction. Feed efficiency significantly improved in fish fed the 14% lipid diet (relative to fish fed the 6% lipid diet) but was not affected by vitamin E levels or the interaction between vitamin E and oil levels. Whole body moisture significantly decreased and lipid increased in fish fed the highest (14%) lipid diet. Dietary vitamin E levels had no effect on body moisture but body lipid significantly increased in fish fed the diet supplemented with 100 mg/kg of vitamin E. Body protein and ash content were not affected by dietary levels of lipid or vitamin E. There was no significant interaction between dietary levels of lipid and vitamin E on body proximate composition. Hematological parameters (red and white blood cell counts, hematocrit and hemoglobin) and hepatosomatic indices were not affected by dietary levels of lipid, vitamin E or their interaction. Serum protein was not affected by supplemental levels of vitamin E but significantly increased in fish fed the 14%-lipid diet. Lysozyme activity was not affected by dietary lipid levels but increased in fish fed the 200-mg vitamin E diet. Serum complement activity significantly decreased in fish fed 10 or 14%-lipid diets but increased when dietary vitamin E levels wert increased to 100 or 200 mg. These innate immune parameters were not affected by the interaction between dietary levels of lipid and vitamin E. Dietary lipid and vitamin E levels or their interaction had no effect on the resistance of tilapia to S. iniae infection and antibody production against that bacterium.