Effect of dexamethasone on differential white blood cell counts and heterophil / lymphocyte ratio in Japanese quails (Coturnix coturnix japonica)

Laying Japanese quails (n = 60), 30 weeks of age reared at the experimental laboratory unit of the Faculty of Technology, Maha Sarakham University, Maha Sarakham province, Thailand. Birds were in cages with wire floors. Randomized Complete Block was the design of the experiment. During the first 4 days of experimental period, quails were fed on a standard commercial diet with four treatments: supplemented with dexamethasone at 4 levels namely 0 (control group), 1.25, 2.50 and 5.00 mg/kg diet. On days 1, 3, 7, 10 and 14 of the experimental period, percentage of heterophil, lymphocyte, monocyte, basophil, eosinophil, and heterophil/ lymphocyte ratio values of laying quails were examined. The results revealed that percentage of heterophil of laying quail with added dexamethasone at 1.25 and 2.50 mg/kg in diets were significantly higher than others (P<0.05). Percentage of lymphocyte of Japanese quails receiving dexamethasone at 1.25 and 2.50 mg/kg was significantly lower than birds receiving dexamethasone at 0 and 5.00 mg/kg (P<0.05). Heterophil: lymphocyte ratio of laying birds supplemented with dexamethasone at 1.25 and 2.50 mg/kg in diets was significantly higher than that of laying quail that added dexamethasone at 0 and 5.00 mg/kg in diets (P<0.05). The percentage of monocyte, basophil and eosinophil after receiving dexamethasone each levels were not significantly different (P>0.05). After discontinuing dexamethasone administration on day 4 of the experimental period, percentage of heterophil, lymphocyte and eosinophil, monocyte, and heterophil: lymphocyte ratio, of quails recovered to normal within 10 days.