Effects of dietary Pennyroyal essential oil on growth performance, digestive enzymes' activity, and stress responses of common carp, Cyprinus carpio

This study aimed at assessing the effects of dietary Pennyroyal essential oil (PE) supplementation on growth performance, digestive enzymes, and stress, antioxidant, and immunological responses to an acute stress. Four experimental diets containing 0 (C), 100 (100PE), 250 (250PE), and 500 (500PE) mg/kg PE were used in this experiment. The fish were fed with these diets for eight weeks, followed by a 3-h crowding stress (40 kg/m3) and 24-h recovery. Growth performance, intestinal amylase, lipase, and protease activities, plasma total protein, albumin, and globulin levels were determined before stress, whereas plasma cortisol, glucose, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lysozyme, alternative complement (ACH50), total immunoglobulin (Ig), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and malondialdehyde (MDA) were measured before and after stress. Dietary PE supplementation significantly increased growth performance and digestive enzymes of the fish. The highest growth performance was observed in 250PE treatment. Highest amylase, lipase and protease activities were observed in 500PE, 250PE, and 250PE/500PE treatments, respectively. Dietary PE significantly increased plasma total protein, albumin, and globulin and decreased plasma triglyceride and cholesterol levels. Dietary PE supplementation significantly decreased cortisol, glucose, ALT, AST, and MDA before the crowding stress and mitigated the elevations in these parameters after stress. On the other hand, dietary PE significantly increased plasma lysozyme, ACH50, total Ig, SOD, CAT, and GPx before stress and mitigated the alteration in these parameters after stress. In conclusion, dietary PE at 250 mg/kg is recommended for common carp feed, as it improve growth performance, digestive enzymes’ activities, and physiological and immunological responses to acute stress in fish.