Abstract

The present study evaluated the effects of a commercial phytogenic feed additive (PFA) on Salmo salar growth, immune response and its susceptibility to Piscirickettsia salmonis infection. Preliminary in vitro trials in SHK-1 cells showed higher expression levels for il-12 and ifn-I genes at 12 h post-treatment, also a protective cellular effect against the P. salinonis infection was observed. Subsequently, in vivo trials with the PFA supplemented diet (0.5 g/Kg) were conducted to corroborate the fish immune modulation and protection against P. salmonis. Diets with and without the PFA were used to fed triplicate groups of 35 juveniles salmon during 14 days. Afterwards, fish from all dietary groups were equally redistributed in tanks and challenged by cohabitation with P. salmonis infected fish (donors), recording mortalities after 70 days post-infection. Survival percentages of 79.1 +/- 3.7 and 52.7 +/- 2.78% were observed in the cohabitant fish fed with PFA and control diets, respectively. PFA dietary administration, preceding the cohabitation challenge, contributed significantly in the protection against P. salmonis as suggested by the Relative Percent Survival (RPS) values of 48.1% after 70 days post-infection. Furthermore, we also demonstrate that dietary supplementation with the PFA stimulates the expression of keys genes involved in the S. solar immune response against P. salmonis infection.