Effects of walnut (Juglans regia) green peel extract on growth performance and challenge to enteric redmouth disease (Yersinia ruckeri) in rainbow trout (Oncorhynchus mykiss)

This study aimed to investigate the effects of walnut (Juglans regia) green peel extract on growth performance parameters growth performance and challenge to enteric redmouth disease (Yersinia ruckeri) in rainbow trout (Oncorhynchus mykiss). The triplicate experimental study was performed for 105 days to evaluate the effect of 1, 2, and 4 mg kg-1 of walnut green peel extract (WPE). Although there was no significant difference in growth performance between the groups, the growth performance and survival rate of the extract-added groups were slightly better than the control group. Some blood parameters procalcitonin (PCT), platelet large cell ratio (P-LCR), and cholesterol (CHOL) values significantly improved in walnut green peel extract-added groups. Phagocytic activity (PA), lysozyme activity (LA), and myeloperoxidase activity (MPO) were significantly increased between all groups compared with the untreated group. Although respiratory burst activity (RBA) increased, no significant difference existed between groups. As a result, it was determined that although walnut green peel extract does not directly affect growth performance, it can be used as a feed additive with its immunomodulatory aspect.