Multi-species probiotics enhance survival, growth, intestinal microbiota and disease resistance of rohu (Labeo rohita) larvae

Abstract

Multi-strain probiotics provide the most dependable approaches to improve health, immune response, and disease resistance in farmed fishes. In the present study, we examined the effects of multi-species probiotics on the survival, growth, immune response, and disease resistance of rohu (Labeo rohita) larvae. Newly hatched larvae from the day of first feeding (average weight of 0.003 ​g) were reared with multi-species probiotics having a combination of Bacillus subtilis (10⁹ colony forming units (cfu)/mL) and Lactobacillus spp. (Lactobacillus plantarum, Lactobacillus buchneri - 10¹¹ ​cfu/mL) in water containing doses of 0 (control-C), 0.5 ​mL/L (treatment 1-T1), and 1.0 ​mL/L (treatment 2-T2) in triplicates for 90 days. After the experiment, a challenge test was performed to assess the fish's resistance to pathogenic Aeromonas veronii. Significantly higher survival was recorded in larvae of treated groups (87% in T2 and 79% in T1) compared to the control (62%). Significantly higher growth performance (weight gain and specific growth rate—SGR) was shown by the probiotic-treated larval groups compared to the control. Probiotic supplementation resulted in significantly higher counts of total viable colony (TVC) and lactic acid bacteria (LAB) in the intestine. Some immunological parameters (mucosal fold fattening, goblet cell abundance, expansion of lamina propria and enterocytes) of the gut were significantly better in probiotic-treated fish. The liver of treated fish showed irregular shape nuclei turning into regular shape and reducing spaces between the hepatic cells. Probiotic-treated fish had the highest post-challenge survival rate (90%) against A. veronii infection. The erythrocytes of challenged fish treated with probiotics had significantly lower frequencies of various nuclear and cellular abnormalities. These findings suggest that multi-species probiotic supplements could improve the survival, growth, health status, and immune response of rohu in the early stages of its development.