We examined the expression of 11 genes in ovine whole blood by using two commonly accepted softwares (geNorm and NormFinder). Both software algorithms are frequently used and freely available but have a different working rationale. NormFinder selects out of a set of potential reference genes one single best-performing reference gene that shows the least variation within the analysed group. GeNorm focuses on pairwise comparisons of reference gene expression in the experimental samples and so is less appropriate for identifying co-regulated genes [18] . To avoid possible bias, we therefore selected the candidate reference genes on the basis of differences in their physiological functions.