Growth Performance, Digestive Enzymes Activities and Gut Microbiota of Malaysian Mahseer, Tor tambroides Fingerlings Affected by Various Probiotics Concentrations

The most valued freshwater fish in Malaysia is the Malaysian mahseer, Tor tambroides, also known as Empurau. Due to the extended growing period, innovative feeding management is required to maintain fish health. This study looked at the effect of Lacto-sacc, a feed additive and antibiotic replacement made up of Lactobacillus acidophilus, Saccharomyces cerevisiae and Enterococcus faecium, on T. tambroides fingerlings’ growth performance, digestive enzyme activities and gut microbiota. A total of 600 fingerlings, each weighing 6.53 g ± 0.17 g, were allocated into twelve 650 L tanks, with 50 fingerlings per tank. Over a period of 20 weeks, the fish were fed four different diets: 0% Lacto-sacc as control (A), 0.5% Lacto-sacc (B), 1.0% Lacto-sacc (C), and 1.25% Lacto-sacc (D), with each diet replicated in three tanks. Although statistic revealed no significant differences in growth performance among treatment group (p>0.05), but it is noteworthy that fingerlings of T. tambroides were fed a diet containing 0.5% Lacto-sacc exhibited a trend toward improved growth performance with value higher SGR, along with elevated lipase and protease activities than other groups. Fusobacteria, Proteobacteria, Bacteroidetes, Firmicutes were the top four phyla in the gut microbiota of T. tambroides, accounting for more than 95%, with Fusobacteria dominating at around 70% of the gut microbiota. Cetobacterium, ZOR0006, Brevinema, and Aeromonas were the most common genera detected. T. tambroides fed a 0.5% Lacto-sacc (B) diet had lower Fusobacteria abundance while increasing other dominating bacteria compared to other treatments. Although there is no significant difference in gut microbiota, the gut microbiota of T. tambroides fed probiotics was more consistently disturbed and diversified, indicating less species dominance. The addition of Lacto-sacc, particularly at a concentration of 0.5%, appeared to enhance growth performance and increase the activity of digestive enzymes compared to the diet without Lacto-sacc, although the results were not statistically significant.