Stimulatory effects of dietary savory (Satureja hortensis L.) ethanolic extract on growth, digestive enzymes, immune parameters, antioxidant defense, and immune and antioxidant-related genes in zebrafish (Danio rerio)

Abstract

The current investigation focused on examining the growth performance, immune and antioxidative factors, and mRNA levels of immune and antioxidant-related genes in zebrafish (Danio rerio) that were fed with different levels of savory (Satureja hortensis L.) ethanolic extract (SEE) for 8 weeks. To achieve this objective, a total of 240 zebrafish with a mean weight of 65.37 ± 5.9 mg were fed on 0.0 (the control; T0), 0.5 % (T0.5), 1 % (T1), and 2 % (T2) of SEE for a period of 8 weeks. The results for the growth performance of zebrafish showed that the final weight (165.20±1.92 mg), Weight gain (147.71±1.15 mg), specific growth rate (1.62±0.03) was significantly (P < 0.05) enhanced with the dietary SEE levels and the best performance was noted in T1 and T2. highest activity levels of α-amylase (53.56±1.21), lipase (3.56±0.16), proteases (13.78±0.21), pepsin (0.31±0.01), chymotrypsin (0.44±0.01), and trypsin (0.68±0.01) were observed especially T2 (P < 0.05). The results of tissue and mucus immune factors revealed that feeding the fish on SEE diets significantly increased the immune activity represented by lysozyme, total Immunoglobulin (Ig), Immunoglobulin M (IgM), total protein, and ACH50 (P < 0.05). The malondialdehyde value was significantly (P < 0.05) affected by experimental diets and its lowest value was notably observed in T1 and T2 than those in T0 and T0.5. The tissue and mucus activity of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and total antioxidant activity (TAC) increased considerably (P < 0.05) in the treatments fed with SEE, and their highest levels were detected in T1 and T2. The relative mRNA expression of CAT, SOD, GPx, and glutathione reductase (GSR) genes in treatments fed with different SEE levels was higher than those in the control group. The relative expression of Lysozyme was notably higher, meanwhile the expression of genes including Interleukin 1β (IL.1B), Interleukin 8 (IL8), and Tumor necrosis factor (TNF-α), significantly decreased in fish fed with SEE; especially at T1 and T2. The present study, 1–2 % savory ethanolic extract of SEE improved the performance, immune, and antioxidant levels.