Effects of dietary Persian hogweed (Heracleum persicum) powder on growth performance, hematological and immune indices, and resistance against Yersinia ruckeri in rainbow trout (Oncorhynchus mykiss)

The current study was performed to evaluate the effect of dietary Persian hogweed (Heracleum persicum) powder (PHP) on growth, hematological and immunological parameters in rainbow trout. The fish with an average weight of 23.38±0.58 (g) were randomly assigned into five groups in triplicates. Diets were prepared by supplementing five levels of 0 (control), 0.5, 1, 1.5, and 2% PHP to a basal diet and fed for 60 days. The addition of 2% PHP significantly improved weight gain, specific growth rate, and feed conversion ratio compared to 0.5% PHP during 30 days (p<0.05). PHP also diminished whole-body fat, after 30 days (p<0.05). Hematological factors showed the enhancements of white and red blood cell counts in the fish fed 1 and 1.5% PHP (p>0.05). Moreover, the addition of 2% PHP improved Hb (p<0.05) after 30 days. On the day 60th, WBC count was significantly higher in the fish that received 1.5% PHP than 0.5% PHP (p<0.05). According to the biochemical analysis the highest concentration of alkaline phosphatase was observed in the fish fed with the control diet and 0.5% PHP (p<0.05). In contrast, cholesterol and triglyceride values reduced by PHP levels on day 60 (p<0.05). Immunological parameters indicated that total protein and globulin were significantly improved by the addition of 1.5 and 2% PHP during 60 days (p<0.05). Lysozyme activity was enhanced by the diets containing 1 and 1.5% PHP after 30 and 60 days (p<0.05). Besides, higher resistance against Yersinia ruckeri was obtained by the administration of 1 and 1.5% PHP. Altogether, supplementation of 1.5% PHP is suggested in the diet of rainbow trout because of partially increased immune indices without showing damages to the liver during 30 days.