Location: Aquatic Animal Health Research
Title: Growth, Immune Response and Resistance (Oreochromis niloticus) to Streptococcus iniae Challenge of Nile Tilapia Fed Various Dietary Lipid Sources Authors
Submitted to: Aquaculture Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 15, 2007
Publication Date: August 5, 2007
Citation: Lim, C.E., Aksoy, M., Davis, D., Klesius, P.H. 2007. Growth, Immune Response and Resistance (Oreochromis niloticus) to Streptococcus iniae Challenge of Nile Tilapia Fed Various Dietary Lipid Sources. Aquaculture Conference Proceedings. p.5. 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 vitamins (A, D, E and K), and serve as a source of phospholipids that are important components of cellular structure. There is evidence that dietary lipids 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. The effect of dietary lipid sources on immunity and disease resistance in tilapia has not been examined. This experiment was conducted to determine the effect of dietary lipid sources on growth performance, body proximate composition, hematology, immune response and resistance of Nile tilapia, Oreochromis niloticus, to Streptococcus iniae infection. Six isocaloric (3.2 kcal/g) and isonitrogenous (34% crude protein) semi-purified diets were supplemented with 7% of various sources of lipid: corn oil (CO), beef tallow (BT), menhaden fish oil (FO), linseed oil (LO), and equal combinations of FO+CO+BT or LO+CO+BT. Each diet was fed to tilapia in quadruplicate aquaria to apparent satiation twice daily for 12 weeks. Fish fed the BT-diet exhibited significantly lower weight gain, diet intake, feed and protein efficiency ratios, apparent protein utilization, and survival. Whole-body protein and ash were significantly (P < 0.05) lower and higher, respectively for fish fed the beef tallow-diet compared to those of other diets, but the values of these variables did not differ among fish fed other diets. No significant differences (P > 0.05) were found among hematological values, except for fish fed the FO-diet which had abnormally high red and white blood cell counts. Serum protein concentration, lysozyme activity, and natural hemolytic complement activity were significantly (P < 0.05) reduced in fish fed the BT-diet. The values of these parameters did not differ among fish fed other diets. Post-challenge antibody titer was not influenced by dietary lipid sources. Cumulative mortality 15 days post-challenge with S. iniae was significantly lower (P < 0.05) for fish fed the BT-diet compared to those fed FO- or FO+CO+BT-diets. No significant differences were observed in fish fed other dietary lipid sources.