Protective effect of herbal and probiotics enriched diet on haematological and immunity status of Oplegnathus fasciatus (Temminck & Schlegel) against Edwardsiella tarda

This study determines the effect of diet enriched with the herb Baical skullcap Scutellaria baicalensis, and/or probiotics Lactobacillus sakei BK19 in rock bream, Oplegnathus fasciatus (32 ± 3 g) against Edwardsiella tarda. The changes in haematological parameters, innate immune response, and disease resistance were investigated after 1, 3, and 6 weeks. The white blood cell count (WBC: 104 mm−3), red blood cell count (RBC: 106 mm−3), and haemoglobin (Hb: g dl−1) levels significant increased (P < 0.05) with mixed diet on 3rd and 6th week and probiotics enriched diet on 6th week. The haematocrit (Ht: %) level significantly increased (P < 0.05) when fed with mixed diet on weeks 1–6. Interestingly, in mixed diet group the lymphocytes (LYM), monocytes (MON), and neutrophils (NEU) significantly increased from week 1–6. The eosinophils (EOS) significantly increased in all the treated groups. In the probiotics or mixed diet groups the total protein (TP: g dl−1) increased significantly on weeks 3 and 6. The serum lysozyme activity significantly was enhanced in all the treated groups indicating an increase in the innate immunity level. Serum complement, antiprotease activities, reactive oxygen species (ROS) and reactive nitrogen species (RNS) production significantly increased from week 1–6 with mixed diet. The maximum protection against E. tarda was recorded in mixed diet group with a minimum cumulative mortality of 20% and a high relative percent survival (RPS) of 72.84. In the probiotics and herbal diet groups the cumulative mortality was 25% and 35% and RPS was 68.63 and 59.42, respectively. This study indicates that administration of probiotics or mixed diets can effectively minimize the mortality and restore the altered heamatological parameters and enhancing the innate immunity in O. fasciatus against E. tarda.