This study evaluates the effect of probiotics, Zymetin, on the immune efficiency of Macrobrachium rosenbergii juvenile against pathogenic Vibrio spp. and Aeromonas spp. The experiment was conducted in glass aquaria with same level of feeding under different treatments, that is, negative control (Cn), positive control with Vibrio spp. (Cv) and Aeromonas spp. (Ca), prawn juveniles fed with probiotics (Zymetin) at 5 g/kg of feed but without pathogen (T1), probiotic fed prawn challenged with Vibrio spp. (T2) and Aeromonas spp. (T3). The results demonstrated that T1 showed higher survival rate, total haemocyte count, non-granular haemocyte count, phagocytic activity, and clearance efficiency compared to other treatment groups. In contrast, decreased number of small and large granular haemocyte was observed in T1.Despite that, THC was found to be significantly different (p < 0.05) among all the controls and lowest was in Cv, followed by Ca. Besides, phagocytic activity and clearance efficiency against Vibrio spp. and Aeromonas spp. decreased significantly in Cn, Ca, and Cv fed M. rosenbergii juvenile, while the values were found to be higher in T1 followed by T2 and T3, in that order. In addition, the challenge test showed an increasing trend of total and beneficial bacterial density as well as declining trend of some harmful bacteria in the water and gut of prawn in all the groups tested (p < 0.05).
K E Y W O R D Sclearance efficiency, Macrobrachium rosenbergii, phagocytic activity, probiotics wileyonlinelibrary.com/journal/are Aquaculture Research. 2019;50:644-657. 2 | MATERIALS AND METHODS 2.1 | Pathogen isolation, culture, and biochemical confirmation Before conducting the challenge test, the pathogenic bacteria (i.e., Vibrio spp. and Aeromonas spp.) were isolated from four diseased prawns which displayed typical symptoms of inactivity, poor growth leading to weight loss, anorexia, and frequent mortality. All the diseased GFP were collected from the farmer's pond of Dumuria, Khulna, Bangladesh. Infected prawns were brought to the Fish Pathology Laboratory of Fisheries and Marine Resource Technology AZAD ET AL.| 645
