Evaluation of the Effect of Extracellular Polymeric Substance (EPS) from Lactobacillus plantarum (LP) on the Disease Resistance of Rice Field Eel (Monopterus albus) Fingerlings

The experiment aimed to determine the appropriate level of EPS to supplement in the feed M. albus to help increase their resistance to diseases caused by the Edwardsiella tarda T4 strain. The experiment included 6 treatments, with 3 repetitions, consisting of 2 control treatments: positive and negative control; and 4 treatments with supplements of 4 g/kg, 6 g/kg, 8 g/kg, and 10 g/kg of feed, conducted at the aquaculture facility of An Giang University. The experiment was conducted over a period of 6 weeks using fingerling M. albus with an average weight of 3–5 g per fish. Each experimental tank was stocked with a density of 250 fish per tank. The results of monitoring environmental factors such as pH, temperature, and dissolved oxygen were all suitable for the growth of M. albus, with values ranging from 25.9 ℃ to 30.6 ℃ for temperature; 4.8 to 6.2 mg/L for dissolved oxygen (DO); and pH ranging from 7.58 to 8.03. The results showed that supplementing with an EPS level of 8 g/kg of feed after 4 weeks was the most effective compared to the other treatments (p<0.05). The survival rate (SR) reached 96.67% after exposure to the pathogenic bacterium E. tarda T4, and the effectiveness of EPS usage relative percentage survival (RPS) was 88.89%. The density of red blood cells and white blood cells reaches the highest levels, respectively 3.03 x 106 cells/mm3 and white blood cells 1,404.63 x 103 cells/mm3; lymphocyte 2,464.35 x 103 cells/mm3 and monocytes 185.84 x 103 cells/mm3. The recorded results indicate that EPS helps stimulate the immune system of the eel and has the potential to prevent disease. Thus, EPS produced from LP bacteria has the ability to resist diseases caused by the E. tarda T4 strain on M. albus, with the most suitable dosage being 8g/kg of feed for 4 consecutive weeks. Keywords: An Giang University, rice field eel fingerling, E. tarda T4, extracellular polymeric substance (eps), hematological parametres.