Comparative performance of Eucalyptus globulus Labill. and Allium sativum Linn. extracts in reducing the fungal and bacterial load of Persian sturgeon (Acipenser persicus Borodin) eggs during the incubation period

Medicinal plants have a much healthier effect than chemical drugs, and due to the presence of various effective substances, they can be used in the prevention and treatment of many diseases. This research aims to compare the performance of hydroalcoholic extracts of eucalyptus and garlic in reducing the fungal and bacterial load of Persian sturgeon (Acipenser persicus) eggs during incubation. At first, enough sperm and eggs were obtained from Persian sturgeon male and female breeders after artificial propagation stages. After fertilization, the eggs were weighed by a digital scale. The number of eggs per gram, the total weight of eggs per tray, and the final number of eggs stored in the incubator were calculated. Considering the allocation of three trays for each treatment, the number of stored eggs for each treatment was 15000. The total number of stored eggs for five treatments was 75000. Hydroalcoholic extracts (70% ethanol solvent) of eucalyptus (appearance: clear, color: brown, pH=5.02) and garlic (appearance: clear, color: light brown, pH=6.49) were prepared. Five experimental treatments containing control (no extract), Eucalyptus 50 mg.l-1, eucalyptus 100 mg.l-1, Garlic 50 mg.l-1, and 100 mg.l-1 were designed in three replicates by the short-term bath method in three stages (days). At the end of the three disinfection stages, eggs were randomly sampled from each replicate for the total bacterial and fungal count. No significant difference was observed in the water's physical and chemical factors, such as pH, dissolved oxygen, and temperature, during the disinfection stages of eggs (p<0.05). The results showed that treatments containing eucalyptus and garlic extracts at 50 and 100 mg/l showed lower total bacterial and fungal counts than the control treatment (P<0.05). Still, the eucalyptus extract at 100 mg/l performed much better than the rest of the experimental treatments (P<0.05). In incubation indices such as hatching rate and healthy larvae, statistically significant differences were observed in four treatments containing garlic and eucalyptus extracts (50 and 100 mg.l-1) with the control (P<0.05). Based on Duncan's test, the average rate of hatching and the number of healthy larvae were more in eucalyptus at 100 mg.l-1 than in other studied treatments (P<0.05). Egg hatching rates were equal in garlic and eucalyptus at 100 and 50 mg.l-1, respectively. During the research, there was no change in the appearance of the larvae, which can be considered the safety of plant extracts. Various factors such as the type and compounds in the plant, the amount of used concentration, the type of microorganism, the pH level, and the environment's temperature can influence the antimicrobial potential of herbal extracts and compounds. According to the obtained findings, it can be stated that hydroalcoholic extracts of Garlic and Eucalyptus played a very decisive role in reducing the fungal and bacterial contamination of Persian sturgeon eggs during the incubation period.