|Davis, D. Allen - AUBURN UNIVERSITY|
Submitted to: Global Aquaculture Advocate
Publication Type: Abstract Only
Publication Acceptance Date: April 10, 2008
Publication Date: July 1, 2008
Citation: Lim, C.E., Aksoy, M., Davis, D., Klesius, P.H. 2008. Effects of Varied Dietary Lipid Sources Tested in Tilapia Study. Global Aquaculture Advocate. 11(3): 68-70. Technical Abstract: Dietary lipids are an important source of highly digestible energy and are the only source of essential fatty acids required for normal growth and development. They are also carriers and assist in the absorption of fat-soluble nutrients, such as sterols and vitamins A, D, E and K, serve as a source of phospholipids and participate in the synthesis of hormones, prostaglandin and other metabolically active compounds. There is evidence that dietary lipids and their constituent fatty acids influence immune response and disease resistance in fish. A deficiency or an excess of n-3 fatty acids have been shown to suppress immune function and increase the susceptibility of fish to infectious pathogens. A study was conducted to evaluate the effects of different lipid sources, namely corn oil (CO), beef tallow (BT), menhaden fish oil (FO), linseed oil (LO), and combinations of equal levels of FO+CO+BT or LO+CO+BT on the growth performance, whole body proximate composition, immune responses and resistance of Nile tilapia to Streptococcus iniae infection. Results show that tilapia appear to have dietary requirements for both linoleic (n-6) and linolenic (n-3) series of fatty acids. Fish fed the BT-diet that are low in these fatty acids had poorer survival and growth performance than fish fed diets containing other lipid sources. High dietary levels of either n-6 or n-3 may spare the requirement of the other, but n-6 appeared to have a better growth promoting effect than n-3. Excessive levels of n-3 highly unsaturated fatty acids in the diet with fish oil may lead to abnormally high red and white blood cell counts, and excessive mucus production. Deficiency of essential fatty acids (BT-diet) leads to decreased immune responses. However, this did not translate into reduced resistance of fish to S. iniae challenge.