Effects of Vitamin C and E Administration on Leukocyte Counts in Rainbow Trout (Oncorhynchus mykiss)

White blood cells (WBC) or Leukocytes are defense mechanism indicators in fishes. Vitamins C and E are among the most important nutrients, providing protection to the leukocytes and subsequently nfluence the fish health and immune system. This study was conducted to investigate the effects of different levels of vitamins C and E (0, 100, 200 and 1000 mg/kg diet) on leukocyte counts of rainbow trout fingerlings during 60 days of feeding trials. The results showed that vitamin E administration increases significantly (P< 0.05) the percent of the lymphocytes at 200 and 1000 mg/kg treatments. In addition, a significant increase (P< 0.05) was found in lymphocytes of fish fed with 1000 mg/kg vitamin C administration. No significant effects of different levels of Vitamins C and E on neutrophils, eosinophils and monocytes were found during the 60 days experiment (P>0.05). The results revealed that administration of Vitamins C and E can be led to a significant increase in lymphocytes that may influence immune response and resistance against disease.