IMMUNOSTIMULANTS FOR GROWTH, INTESTINAL HEALH, IMMUNE RESPONSE AND STREPTOCOCCUS AGALACTIAE CHALLENGE SURVIVAL OF TILAPA (OREOCHROMIS NILOTICUS)
Introduction
The gut barrier function is vital in gut health and maintaining the general health of fish (Jutfelt, 2011, Sundh, 2009). Impairment of the intestinal barrier is a key even in various gastrointestinal diseases (Mennigen and Bruewer, 2009). In fish, the gastrointestinal tract is the site of food digestion and nutrient uptakes as well as a primary barrier that prevents entrance of harmful agents (Niklasson et al., 2011). In depth knowledge about the intestinal health of fish is essential. PresanTM-FX a commercial Feed Additive from Selko, a Nutreco company, is a synergistic blend of phenolic compound, slow release C12, target release butyrate, MCFAs and organic acids. Studies suggests PresanTM-FX stabilise the gut microbiota and boost the gut barrier integrity. Glucan Plus is an immunostimulant combination including 1,3 - 1,6 ß-Glucan and essential oil property of Skretting, a Nutreco company. Glucan Plus is designed to stimulate non-specific immunity and inhibit pathogenic bacteria. The purpose of the present study is to further evaluate the effects of immunostimulants containing either fermentable saccharides and short chain medium fatty acids or ß-Glucan and essential oil on tilapia gut health, in terms of intestinal histology, immune balance and disease resistance. The secondary effects on growth performance also determined.
Materials and Methods
Nile tilapia (47.74 ± 1.1g) were randomly allocated to 3 prelicate 170L tanks of 45 fish for each of three diet treatments in running water. A basal diet (30% crude protein, 8% fat) with and without either 2% PresanTM-FX or 0.05% Glucan Plus were fed to the animals for 10 weeks. At the end of feeding trial, from each of tank, 28 fish were selected for a challenged by immersion in 109 CFU/ml Streptococcus agalactiae for 1 hour. Rate or mortality is observed and compared for 14 days. At the end of feeding trail, growth performance and feed utilisation are assessed. At week 2, 6, 10, 11 and 12 fish per replicate tank were sampled for immune assays and gut histology analysis. The proximal, middle and distal intestine were also processed for quantitative histology.
Results
Conclusion
Supplementation of PresanTM-FX in Nile tilapia diets for 10 weeks has been shown to significantly enhance gain weight and feed conversion ratio. Although ssupplementation of Glucan Plus in diets did not affect growth but significantly improve immune balance indicated by lysozyme activity and gut health. Glucan Plus significantly reduced mortalities of Nile tilapia against Streptococcus agalactiae by 68.6 %.
References
Jutfelt, F. (2011) INTEGRATED FUNCTION AND CONTROL OF THE GUT | Barrier Function of the Gut In Encyclopedia of Fish Physiology (Editor-in-Chief: Anthony, P.F. ed.), pp. 1322-1331. Academic Press, San Diego.
Mennigen, R. & Bruewer, M. (2009) Effect of Probiotics on Intestinal Barrier Function. Annals of the New York Academy of Sciences, 1165, 183-189.
Niklasson, L., Sundh, H., Fridell, F., Taranger, G.L. & Sundell, K. (2011) Disturbance of the intestinal mucosal immune system of farmed Atlantic salmon (Salmo salar), in response to long-term hypoxic conditions. Fish & Shellfish Immunology, 31, 1072-1080.
Sundh, H. (2009) Chronic stress and intestinal barrier function. Implications for infection and inflammation in intensive salmon aquaculture In Department of Zoology, Vol. PhD, pp. 72. University of Gothenburg, Sweden, Department of Zoology.
