Stress Assessment by the Hemogram Method - Circulating Cells Complicating Reliance on Heterophil/Lymphocyte (H/L) Ratio

The subject is a reexamination of the utility of the heterophil/lymphocyte ratio as a stress measure. The data are obtained from blood films of non-experimental chickens at 3 weeks of age and housed in isolator units. Standard differential counts of 2 x 200 cells indicated total white blood counts (TWBC) were in the range of 30-200(K) with an average of ~100(K); normal to leukemoid reaction levels (N= 23 samples). The H/L average of ~ 0.5 was typical of a non-stress hemogram. However, many atypical cells were identified including small lymphocytes with irregular cell membranes (zeiosis) reactive lymphocytes, resting (small) or activated NK (natural killer lymphocytes) unusual heterophils of three types: classic (HC), typical (HT), variant (HV), and early stages of the granulocyte series. Aggregates of atypical cells (reactive clusters) were also common. Atypia were present in blood samples at all TWBC and H/L levels. These hematological conditions suggest that estimates of stress status solely reliant on H/L data may not convey an accurate blood picture. It is necessary to integrate the calculated H/L with the TWBC and the occurrence of atypical cells to more accurately determine homeostasis.