Effect of ascorbic acid on respiratory rate, body temperature, heterophil: lymphocyte ratio and microscopic lesion score in lung, liver, kidney, Cardiac muscle and spleen in broilers under chronic heat stress

摘要

The purpose of this experiment was to investigate the effects of ascorbic acid on pathophysiology of broilers under chronic heat stress. Broilers, 28 days old were maintained at 26-28 deg C and subjected to a daily 5 h episode of heat stress at 33+-1 deg C environmental temperature and supplemented with four levels of ascorbic acid i.e. o (control group), 200, 400 and 800 mg/kg in their diets for 21 days. Birds fed with ascorbic acid at 400 and 800 mg/kg of the diets, had a significantly lower respiratory rate than the control group (P<0.05). Broilers fed with ascorbic acid at 400 mg/kg in the diet had an increased body temperature that was significantly higher than the control group (P< 0.05). Feed intake of broilers fed with added ascorbic acidat 0, 200, 400 and 800 mg/kg in their diets were not significantly different (P>0.05). In addition, the heterophil: lymphocyte ratio of the birds that fed on added ascorbic acid at 200 mg/kg in the diet was significantly higher than the control group. Hemorrhagic lung lesion scores of broilers that were under added ascorbic acid at 400 mg/kg in the diet were significantly lower than the control group (P<0.05). Scores of pathological changes in lung tissue of the control broilers were significantly higher than in broilers fed on ascorbic acid at 400 mg/kg in the diet (P< 0.05). Liver cell degeneration scores of birds fed with added ascorbic acid at 200, 400 and 800 mg/kg in diets were significantly higher than the control group (P< 0.05), and liver celldegeneration scores of the group that received ascorbic acid at 800 mg/kg in diets were significantly higher than in birds fed with ascorbic acid at 200 and 400 mg/kg in diets. Birds, receiving ascorbic acid at 200, 400 and 800 mg/kg in diets for 21 day, had kidney hemorrhage scores significantly higher than the control group (P< 0.05). Cardiac muscle damage scores of broilers fed with ascorbic acid at 400 mg/kg in the diet were significantly higher than all other groups (P<0.05). In addition, splenicwhite pulp scores of birds receiving ascorbic acid at 200 mg/kg in the diet were significantly higher than in birds fed with added vitamin at 800 mg/kg in the diet and the control group (P< 0.05). These finding indicated that ascorbic acid added in the diet for 21 days caused liver and kidney injury even though this vitamin could reduce heat stress, respiratory rate and lung damage in broilers under chronic heat stress.