Stimulatory effect of dietary butyrate on growth, immune response, and resistance of Nile tilapia, Oreochromis niloticus against Aeromonas hydrophila infection

Abstract

Acidifiers could be used as feed additives to stimulant performance, health, and immunity of fish fed plant-based diets. In the present study, sodium butyrate (SB) was incorporated in practical diets for Nile tilapia, Oreochromis niloticus (L.) to alleviate the adverse effects of high contents of plant ingredients in fish diets. However, Gustor BP-70 (Norel Misr), which is a protected SB (70%) coated with 30% of vegetable fat, was incorporated in a practical fish diet at levels of 0.0, 2.5, 5.0, 7.5, and 10.0 g/kg diet. Fish (5.4 ± 0.5 g) were fed the tested diets manually up to apparent satiation twice a day for 90 days in quadruplicates. At the end of the feeding trial, fish were intraperitoneally injected by pathogenic bacteria, Aeromonas hydrophila and kept under observation for 10 days to record any irregular clinical signs and daily fish mortality. Dietary SB showed stimulating-effects on fish growth, feed utilization, and innate immunity of Nile tilapia. Likewise, activities of serum lysozyme and respiratory burst as well as bactericidal and agglutination activities were significantly improved due to dietary SB supplementation in a dose-dependent trend. After A. hydrophila infection, no fish mortality was detected in fish fed 7.5–10.0 g SB/kg diet, whereas fish fed the control diet showed highest mortality (85.0%). Based on the regression curve, it could recommend the use of 6.25 g SB/kg diet as a feed supplement for Nile tilapia to enhance its performance, immunity, and resistance against the possible infection by pathogenic bacteria A. hydrophila.