Effect of a Monoglyceride Blend in Nile Tilapia Growth Performance, Immunity, Gut Microbiota, and Resistance to Challenge against Streptoccocosis and Francisellosis

This study evaluated the effects of supplementing the diet of juvenile Nile tilapia (Oreochromis niloticus), which weighs approximately 20 g, with a blend of monoglycerides (glycerides linked to a fatty acid molecule) for 20 days during a pre-experimental challenge via the intraperitoneal route (IP). Growth performance, immunological parameters, intestinal microbiota, tissue damage, and resistance against the pathogens Streptococcus agalactiae serotypes Ib and III and Francisella orientalis were evaluated. The experimental design included a negative control (NC), a product control (NPC), a positive control for each pathogen (PC), and three groups treated with different doses (0.15, 0.25, and 0.5%). After the challenge, mortality was significantly lower in the groups treated and challenged with S. agalactiae. The treated groups showed better weight gain and food conversion rates. Innate immunity parameters showed no differences between treatments, and there was no good stimulation of diversity in the intestinal microbiota. However, in treated groups, there was a reduction in opportunistic bacteria that could cause secondary infections and increased the presence of beneficial bacteria in the intestinal tract. In this way, it is possible to validate the beneficial effects of monoglycerides as a nutritional additive for tilapia farms against streptoccocosis.