Effect of vitamin solution on growth, health and stress response of Nile Tilapia challenged with streptococcus agalactiae

Abstract

Stress on Nile tilapia (Oreochromis niloticus) can impact growth and overall health during sensitive circumstances. This study overviews the different lines of fish defenses and illustrates other elements involved in innate and specific immune responses, which various factors (e.g., stressors or environmental aspects of natural origin) could influence. The study has been conducted to evaluate the effect of a vitamin solution on the growth, health, post-injection stress, and resistance of tilapia that were challenged with Streptococcus agalactiae, which has not been investigated before. White blood cells were evaluated to determine stress in the fish at different time intervals following placebo vaccination (saline solution) before challenging Streptococcus agalactiae. Here, fish in treatment Vi 10 were applied at 10 mL/kg of a vitamin solution top coated on commercial feed pellets and no saline injection during 3 weeks of the trial, while fish in Vi 10-Saline treatment was fed similarly but with saline injection on the seventh day to compare sampled cortisol levels as an indication of the stress response. Besides, a Control treatment in which no product application nor injection was included in the experimental design. Finally, 30 fish of each replication per treatment were challenged with S. agalactiae on day 22, and the mortality was followed up for 7 days. There were no significant differences in weight gain, feed intake, and feed efficiency ratio between the three treatments. The hematological parameters and blood cell counts recorded in fish fed with and without a vitamin diet had similar results. The results indicated that adding vitamin solution is essential for tilapia to maintain relative cortisol levels in stressful conditions and potentially improve survival after a pathogenic challenge. Further studies are recommended to optimize the vitamin supplementation regime and rearing conditions for better influence on growth performance.