Comparative ability to tolerate heat between thai indigenous chickens, thai indigenous chickens crossbred and broilers by using heterophil/lymphocyte ratio.

The effects of high environmental temperature on the heterophil/lymphocyte ratio were determined for a comparison of the ability to tolerate heat between Thai indigenous chickens, crossbred Thai indigenous chickens and broilers. One kilogram of the representative males and females of each of the three breeds were maintained in an environmental temperature range of 26 +/- 2 and 38 +/- 2 degrees C. Heterophil/lymphocyte ratio was investigated on day 1, 7, 14, 21 and 28 of the experimental period. The results revealed the following information: For those chickens maintained in an environmental temperature at 38 +/- 2 degrees C, the heterophil/lymphocyte ratio was higher than that of chickens at 26 +/- 2 degrees C. With the environmental temperature at 38 +/- 2 degrees C, the heterophil/lymphocyte ratio of the broilers was significantly higher than that of the Thai indigenous chicken crossbreds and Thai indigenous chickens (p < 0.05), respectively. The heterophil/lymphocyte ratio of the chickens for the environmental temperature of 38 +/- 2 degrees C was significantly increased on day 7 and then significantly decreased to day 14 and 21 of experimental period (p < 0.05). This finding indicated that when chickens were maintained in high environmental temperatures, they were under heat stress. Chickens could adapt to high environmental temperatures. Finally, Thai indigenous chickens and Thai indigenous chicken crossbreds tolerated higher environmental temperatures than the broilers.