FRY TILAPIA (Oreochromis niloticus) ANTIBODY IMPROVEMENT AGAINST Streptococcus agalactiae THROUGH BROODSTOCK VACCINATION

Abstract

Maternal immunity through brood stock vaccination could improve antibody of seed to pathogenic infections. This study was aimed to determine the appropriate time to vaccinate tilapia brood stock using a combination of extracellular product and formaline-killed whole cells S. agalactiae. Therefore, experiments were divided into brood stock injected on day seven after spawning (Group 1), brood stock injected on day 14 after spawning (Group 2) and non-vaccinated brood stock as a control group. Vaccination was performed according to gonadal development stages. Macroscopic observation of gonadal development was conducted on the field using fresh specimen, and then analyzed using histological method. The second stage of gonadal development was observed on day seven, and the third stage (peak of vitellogenesis) on day fourteen post-spawning. The results indicated that vaccination time directly affects the antibody accumulation in fish eggs and seeds and the appropriate time to vaccinate broodstock was on the second stage of their gonadal development.