Evaluation of the Effects of Extracellular Polymeric Substance (EPS) Produced from Lactobacillus plantarum on Growth Performance and Survival Rate of Ricefield Eel (Monopterus albus) Fingerlings

The experiment was conducted by supplementing EPS derived from Lactobacillus plantarum into the feed of ricefield eel fingerlings at concentrations of 0 (control), 4, 6, 8, and 10g/ kg. After continuous feeding for two and four weeks, 90 ricefield eel fingerlings from each treatment group were challenged with the pathogenic bacterium Edwardsiella tarda. The results indicated that the optimal EPS supplementation was 8g/ kg of feed for at least 2 consecutive weeks or 6g/ kg for at least 4 consecutive weeks. At 8g/ kg over 2 weeks, the survival rate reached 93.3%, the specific growth rate (SGR) was 2.81%/day, and the feed conversion ratio (FCR) was 2.35. The relative percent survival (RPS) reached 84.6%, which was significantly higher compared to groups receiving lower EPS levels. Furthermore, prolonged supplementation for four weeks at a dose of 6g/ kg also produced effective results. The survival rate was 93.3%, SGR reached 2.24%/day, FCR was 2.37, and RPS achieved 77.8%, all are significantly different from lower-dose treatments. In conclusion, EPS produced from Lactobacillus plantarum can be effectively supplemented into the feed of ricefield eel fingerlings at 8g/ kg for at least 2 weeks, or 6g/ kg for at least 4 weeks, to achieve optimal growth performance, feed efficiency, survival rate, and disease resistance (RPS).