Effect of dwarf elder (Sambucus ebulus) to improve hemato-immunological and biochemical parameters and resistance against Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss)

The present study examined the effects of dietary dwarf elder (Sambucus ebulus) on hemato- immunological and biochemical parameters and protection against Yersinia ruckeri in rainbow trout. The fish were divided into four groups (in triplicate) and fed diets supplemented with 0, 2.5, 5, and 10% of the powdered leaf of dwarf elder for 8 weeks. The blood samples were taken on weeks 4 and 8 of the trial. The use of dietary dwarf elder did not significantly affect the red bloo cells (RBC), hematocrit, hemoglobin, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC), lymphocytes percentage, glucose, and alanine transaminase (ALT) levels of all the treated groups compared to the control group on weeks 4 and 8. At the same time, the total count of white blood cells (WBC) and the neutrophil percentage in the fish receiving the herb powder were significantly higher than the control group. The highest total protein, albumin, immunoglobulin levels, and respiratory burst activity were observed in 5% group after 4 and 8 weeks. On the 8th week, the lysozyme activity was significantly increased and the triglyceride was significantly decreased in 5 and 10% groups compared to the control group. After 4 and 8 weeks, the treated groups exhibited a significant decrease in the cholesterol and alanine aminotransferase levels compared to the control group. The lowest number of bacterial colonies in the serum antibacterial activity belonged to 5 %, 10 %, 2.5 %, and control groups, respectively. At the end of 8 weeks, the fish were challenged with Yersinia ruckeri and the survival rates of the control, 2.5 %, 5 %, and 10 % groups that were 22.2 %, 60.3 %, 79.5 %, and 68.5 %, respectively. The present findings indicate dwarf elder possesses beneficial dietary effects on immune responses and resistance against Y. ruckeri in rainbow trout.