Effects of dietary Shirazi thyme (Zataria multiflora Boiss) and vitamin E on growth and biochemical parameters in common carp (Cyprinus carpio)

Using phytobiotics as fish feed additives has interestingly increased during the recent decade. The aim of the current study was to evaluate the effect of individual and combined levels of thyme and vitamin E in common carp. Juveniles were separately fed four distinct diets including a control diet (commercial diet without any additive), a diet supplemented with 1% ground Shirazi thyme, diet supplemented with 100 mg/kg vitamin E and a mixture of Shirazi thyme and vitamin E (TE) with mentioned concentrations for 45 days. Sampling was done on days 15, 30 and 45 after the feeding trial duration and some growth and plasma biochemical parameters were evaluated. The individual thyme supplementation significantly increased weight gain (%), feed conversion efficiency and decreased feed conversion ratio (p<0.05). Plasma enzymes (AST, ALT, ALP and LDH) were not affected in all experimental groups. Compared with the control, triglyceride and glucose were significantly elevated in TE complex at all sampling times. Plasma proteins (total protein, albumin and globulin), cholesterol and creatinine were not altered in all treatments. In conclusion, dietary supplementation with individual 1% Shirazi thyme had no harmful effects on plasma biochemical parameters and increased growth performance of the fish. Moreover, positive effects of thyme on fish growth were more than with vitamin E. Supplementation with a mixture of vitamin E and thyme also displayed no superiority than the individual use of Shirazi thyme in the diet.