Effect of Aloe vera and Salvia officinalis extract supplemented diet on hematology, histopathology, and hypoxia resistance in rainbow trout

This study investigated the effects of Aloe vera and Salvia officinalis extracts on hematological and haemato-biochemical parameters, histopathology, and resistance against hypoxia stress in Oncorhynchus mykiss. The rainbow trout (10 ± 0.1 g) were fed seven different diets supplemented with 0% (control), 0.5%, 1% and 1.5% of A. vera or S. officinalis extract for 30 days. The feeding in all treatments was continued for 2 weeks using control diet. The fish blood samples were collected on days 30th and 45th, and total red blood cells, hematocrit and hemoglobin were measured. The glucose and cortisol of serum were examined just before and one hour after hypoxia stress (3 mg L-1) at days 30th and 45th. The gill tissue samples were taken from all treatments for histopathological study at the end of experimental period. The S. officinalis (0.5%) treated group showed a significant increase (p < 0.05) in red blood cells, hematocrits and hemoglobin compared to control group. While the A. vera (1 and 1.5%) treatments revealed significant increase in hematocrit and hemoglobin concentration compared to the control group (p < 0.05). Moreover the glucose and cortisol levels of serum were increased significantly only in S. officinalis (0.5%) treated group after hypoxia stress on days 30th and 45th compared to the control group (p < 0.05). No serious histopathological changes were observed in any treatments and control group. Based on the results obtained, dietary S. officinalis (0.5%) hydroethanolic extract improved the haematological and haemato-biochemical parameters and increased the rainbow trout resistance against hypoxia stress.