Evaluation of Lactobacillus plantarum as feed supplement on host associated microflora, growth, feed efficiency, carcass biochemical composition and immune response of giant freshwater prawn, Macrobrachium rosenbergii (de Man, 1879)

Abstract

The present experimentwas conducted to evaluate probiotic effect of Lactobacillus plantarum on giant freshwater prawn, Macrobrachium rosenbergii. A 90-day feeding trial was conducted by feeding prawn juveniles (mean weight ± SE: 0.54 ± 0.03 g) with three experimental diets prepared by supplementing basal diet (Crude protein: 38%; Gross energy: 387 kcal 100 g−1) with different concentrations of probiotics bacteria viz. T1 (107 cfu g−1 diet), T2 (108 cfu g−1 diet), T3 (109 cfu g−1 diet) and control diet (unsupplemented diet). In the present study, growth parameters viz. WG% and SGR and feed utilization parameters viz. FCE, FCR and PER increased significantly (P b 0.05) in all the experimental groups compared to the control whereas, the improvement observed between T2 and T3 was not significant (P N 0.05). The carcass protein content increased significantly (P b 0.05) with concurrent decrease (P b 0.05) in carbohydrate content when prawn juveniles were fed with diet supplemented with higher dose of probiotic bacteria (T3). The Lactobacillus sp. count increased significantly (P b 0.05) in the gastro-intestinal tract with concurrent decrease (P b 0.05) in gram negative bacteria count in all the experimental groups compared to the control whereas, the improvement observed between T2 and T3 was not significant (P N 0.05). However, Lactobacillus sp. count decreased significantly (P b 0.05) within 7 days after switching to basal diet which indicates that probiotic bacteria failed to sustain its population in the digestive tract of prawn. The immune parameters viz. total hemocyte count (THC), phenol oxidase (PO) activity, respiratory burst (RB) activity and clearance efficiency significantly improved (P b 0.05)with concurrent decrease (P b 0.05) in cumulative mortality against A. hydrophila challenge in all the experimental groups except for T1, where PO and RB activity did not improve significantly (P N 0.05) compared to the control. Among the experimental groups, though the improvement in immune parameters was highest (P b 0.05) in T3, no significant difference (P N 0.05) was observed between T2 and T3. The results obtained fromthe present study indicate that L. plantarum can be used to improve the host associated microflora, growth, feed efficiency, carcass biochemical composition and immune response of M. rosenbergii in the laboratory condition.Moreover, though a dose response was observed in the present study, the improvement was not significant between T2 and T3 and therefore, studies with further higher concentration should be conducted for its efficient commercial level field application.