influence of probiotic, lactobacillus plantarum on serum biochemical and immune parameters in vaccinated rainbow trout (oncorhynchus mykiss) against streptococcosis/lactococosis

this study evaluated the effects of probiotic, lactobacillus plantarum on serum biochemical and some immune parameters of immunized rainbow trout weighting 29.6±1.84 g, with streptococcosis/lactococosis vaccine at 16±1.5°c, for 60 days. a commercial diet was used as the control. fish in the first treatment were immunized with streptococcosis/lactococosis vaccine in bathing route for 1 min. in the second group, the vaccinated trout were also fed diet containing l. plantarum (10 8 cfu g -1 ). in the third treatment, fish were only fed the diet supplemented with l. plantarum (10 8 cfu g -1 ). the results showed that vaccinated trout with or without l. plantarum feeding diets significantly decreased heterophils. meanwhile it enhances serum lysozyme, alternative complement activities, antibody titer, total leukocytes, lymphocytes, and serum biochemical parameters, including alp, igm, and total protein levels compared to control groups. moreover, the highest levels of above mentioned parameters were found in vaccinated fish that fed l. plantarum . in addition, the vaccinated fish that fed l. plantarum showed significantly elevated cholesterol levels compared to the control group. the results showed that the dietary l. plantarum improved the immunity of immunized trout with streptococcosis/lactococosis vaccine.