Observed variation in the heterophil to lymphocyte ratio values of birds undergoing investigation of health status

Analysis of blood has been commonly used in the clinical assessment of the health status of birds and typically encompasses a suite of haematological assays. Determination of the heterophil to lymphocyte (H/L) ratio has been commonly reported as an alternative measure of leukocyte values, particularly in studies of naturally occurring physiological influences on birds. Relatively few studies have assessed the H/L ratio values of birds undergoing haematological assessment as part of an investigation of health status. In the current study, the H/L ratio was retrospectively determined for birds that had undergone a haematological assessment as part of a clinical investigation of health. Of the 176 adult birds assessed, encompassing 70 species and 17 orders within the Aves, the H/L ratio was between 0.19 and 64.67 and was greater than 2.0 in 68.8 % of birds. The current study illustrates that the H/L ratio of birds can be markedly affected by disorders of health which should be considered when interpreting any H/L ratio value. © 2014, Springer-Verlag London.