Ameliorative effects of irradiated rosemary (Rosmarinus officinalis) alcoholic extract on serum biochemical parameters and digestive enzyme activities in rainbow trout (Oncorhynchus mykiss)

There are numerous studies about the positive effects of rosemary on growth performance, digestive enzyme activity, antioxidant and immune systems, and disease resistance in different fish species. On the other hand, the efficacy of γ-irradiation to enhance the biological activities of rosemary has been demonstrated. Therefore, this study aimed to evaluate the potential of rosemary in three forms (crude powder, alcoholic extract, and irradiated alcoholic extract) on rainbow trout (Oncorhynchus mykiss) serum antioxidant system, liver-related enzyme activities, some metabolites and digestive enzyme activities. After synthesizing the alcoholic extract of rosemary, γ-irradiation was performed at 30 kGy with a Cobalt-60 gamma irradiator. In the in vivo trial, fish specimens (~225.36 g) were randomly distributed into four groups with three replicates. After the seven-day adaptation period, fish were fed with the control diet or the treatment diets (crude powder= T1, alcoholic extract= T2, or irradiated alcoholic extract = T3) for 50 days. The results showed that the highest serum glucose level was seen in the control group (118.43±4.16 mg dl-1) whereas the lowest level was noted in the T3 group (41.25±1.59 mg dl-1). In parallel, triglyceride levels decreased in the T2 and T3 groups compared with the control group. Digestive enzyme activities also improved in all treated groups, especially in the T2 and T3 groups, compared to the control group. Liver-related enzyme activities also decreased following the administration of the T3 group. Serum antioxidant enzyme activities also increased in T2 and T3 groups compared with the control group with the highest SOD and CAT activities shown in the T3 group. In conclusion, the present study showed that 50-day dietary administration of rosemary alcoholic extract, especially in the irradiated form, could enhance some serum metabolites, antioxidant enzyme activities, liver-related enzyme activities as well as digestive enzyme activities in rainbow trout.