The fish (84±1.02 g mean±SEM) were divided into 3 groups (N=15 in each group) as
control (CNT), infected with Yersinia ruckeri (INF), and infected and essential oils (+EO).
The CNT and INF groups were fed only with commercial fish feed. The +EO group was
fed with feeds prepared with the rate of 10 ml herbal essential oils (mixed thyme and
fennel) / 100 g feed during 21 days. The liver tissue (0.4 g) of fish was dissected in third
day of the experimental period and mRNA transcription levels in liver tissue were
determined by Real Time PCR analysis. INF and + EO groups exhibited decreased
immunity against the challenging with Y. ruckeri infection (53.57 and 42.85 % mortality,
respectively) when compared with CNT group (93.33 %). Gene mRNA transcription
levels of tumour necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), inducible nitric
oxide synthesis (iNOS), serum amyloid A (SAA), that are responsible during the initiation
and continuation of the inflammation increased in 1.86, 2.46, 1.62 and 55.7 fold change,
respectively in INF group, whereas mRNA expressions of haptoglobin (Hp) decreased
(1.2–fold change) in 3th day of experimental period. The +EO group eliminated the
increase in all of the gene expressions
