A study of blood eosinophil counting in calves

Blood eosinophils were determined in eight 7--13-month-old calves that had been reared under parasite-free conditions. Eosinophil counts were obtained by three methods, a) a direct count, b) a differential count and c) an indirect count (i.e. differential count x total leucocyte count). Methodological errors of these methods were determined. Upper limits of 1,000 eosinophils/micronl (direct count) and 9.5 per cent eosinophils (differential count) have been estimated an suitable working standards for calves of this age group. The distribution of eosinophils was skew, most direct counts being below 700 cells/micronl and most differential counts being below 7.5 per cent. A high degree of correlation was found between results obtained by either method, but an even higher correlation was found between direct and indirect counts.