Effects of dietary earthworm (Eisenia fetida) meal and garlic (Allium sativum) powder on hematological parameters of Rainbow trout (Oncorhynchus mykiss)

Abstract

Finding the suitable substitution for fish meal without any negative effect on fish performance is especially important for aquaculture development. In this research, the effect of substitution of fish meal with different levels of earthworm (Eisenia fetida) meal and garlic (Allium sativum) powder were studied on hematological and serum parameters of rainbow trout (Oncorhynchus mykiss) fingerlings. For this purpose, various diets were prepared containing different levels of substitution of fish meal with 0, 25, 50 and 75% of earthworm meal accompanied by 0 and 2.5% of garlic powder. Fingerlings with the average initial body weight of 30±0.27 g were reared in equal conditions for 56 days in 8 treatments and each treatment had three replicates. At the end of the experiment, the results of blood and serum biochemical indices assessments showed that the highest amounts of hemoglobin, hematocrit and WBC were observed in the treatments containing 25% earthworm meal with garlic powder, 25% earthworm meal with and without garlic powder and 75% earthworm meal without garlic powder, respectively whereas the lowest amount of RBC was observed in the treatment containing 50% earthworm meal without garlic powder. MCV, MCH and MCHC values in the treatment containing 0% earthworm meal with 2.5% garlic powder were significantly higher as compared to those of the other treatments except the control treatment (P<0.05). The highest serum protein level was observed in the treatments containing 0% earthworm meal with 0 and 2.5% garlic powder. The lowest amounts of serum glucose and triglyceride were observed in the treatment containing 25% earthworm meal with 2.5% garlic powder. The lowest amount of cholesterol was observed in the treatments containing 75% earthworm meal with 0 and 2.5% garlic powder. Results showed that different levels of earthworm meal with or without garlic powder improved the amounts of WBC, triglyceride, glucose and cholesterol as compared to those of the control treatment. Serum biochemical indices were significantly affected by the diets containing earthworm meal and garlic powder (P<0.05). It was found that the lowest variations in blood and serum parameters were observed in the treatments containing 25% earthworm meal, whereas garlic powder supplementation improved the negative effects of substitution of fish meal with 50% earthworm meal on some of the hematological parameters.