A 30-day experiment involving 720 White Leghorn layer hens was carried out to evaluate the effects of vitamins C and E on leukocyte and heterophil/lymphocytes ratios of the layer hens during the natural summer conditions. The birds were divided into 4 groups, one control with basal diet and three experimental with diet supplemented with vitamin C, vitamin E, or combination of both vitamins. Each group was divided into 4 subgroups. Exposure of layer hens to 31 ± 3 °C and 33 ± 0 °C ambient temperature and 84.6% and 81.5% relative humidity during the experiment caused an increase in the value of temperature humidity index of 15.5 above the threshold value of 70 established for this species. Total white blood cells, lymphocytes, and eosinophil levels were significantly (p < 0.001) higher in all treated groups compared to control. Similarly, heterophil/lymphocyte ratios of 0.51, 0.52, and 0.50 for groups with diet supplemented with vitamin C, vitamin E and vitamins C + E, respectively, were significantly (p < 0.001) lower compared to 0.59 recorded in the control group. However, heterophil, basophil and monocyte values were significantly (p < 0.001) higher in the control group compared to all treated groups. The results of the present study showed that dietary supplementation of vitamins C and E, or their combination, reduces the harmful effect of high ambient temperature and humidity on the leukocyte indicators of exposed layer hens, thereby alleviating the stress imposed on their thermoregulatory mechanism and physiological status.
Effects of vitamin C and E dietary supplementation on erythrocyte parameters of layer chickens reared in high ambient temperature and humidity
