Automated blood cell count: a sensitive and reliable method to study corticosterone-related stress in broilers

In chickens the heterophil/lymphocyte ratio (H/L) has proved to be a valuable tool in stress related research. In general, H/L is determined with the microscopic differential count on a blood film. We evaluated automated analysis for measuring blood cell parameters in relation to corticosterone in a recently introduced corticosterone model. Discrepancies between microscopic and automated counts were found for the percentage of monocytes and basophils. The relative H/L ratio appeared to be sensitive for increased plasma corticosterone levels. However, the increase in heterophil frequencies measured with the hematology analyzer proved to be the most sensitive method for the measurement of changes in plasma corticosterone concentrations. We therefore propose automated hematological analysis as a simple and sensitive tool to study the effects of physiological corticosterone concentrations on blood cell parameters in relation to stress in broiler chickens.