Aviary Caged Hens with Unusual Lymphocytes and Normal H/L Ratios

The aim is to describe hemograms of hens that bear upon interpretation of the traditional H/L stress determination method. Hemograms from aviary caged (AV) commercial hens sampled at 18 wk with low to moderate heterophil/lymphocyte ratios (H/L, range 0.02 – 0.66) were accompanied by slightly elevated total white cell counts (TWBC ~ 30K/μL) to leukocytosis (TWBC ~ 120K/μL) levels. Atypical cells were commonly seen in Wright-Giemsa stained blood by standard differential counts (SDC). Heterophils exhibited signs of toxicity affecting both the nucleus, the cytoplasmic granules, and cell membranes. Many forms of atypical lymphocytes were also detected. These were aggregated small lymphocytes (Ls), medium sized reactive lymphocytes (Lm) plasmacytes (PC) including Mott cells, and other atypical forms. Some PCs contained pink cytoplasmic vacuoles (Russell bodies) an indicating they are IgA types. Developmental PCs rarely found in the circulation of homeostatic avians were also present. Bacteria were commonly associated with the atypical cells. These were both free swimming and cell associated (CAB) types. Fungal forms were also present including yeast-like conidia and hyphae. When microorganisms were in a field the background erythrocytes were in Rouleaux formation, an indication of an inflammatory milieu. In conclusion, it is demonstrated that in the absence of detailed cytological descriptions the H/L ratio can be misleading. Given its wide usage in stress and welfare determinations these observations emphasize some of the difficulties of the simple H/L method. They reinforce earlier observations and draw attention to the necessity of cytological detail before the computed H/L ratio can be accepted as a stress measure.