NormFinder ranks a set of candidate genes according to their expression stability measure (ρ) based on the similarity of their expression profiles. Lower values are assigned to the most stable genes. Table 2 reports the results of the NormFinder analyses. The ranking appears to be consistent to the one previously determined using geNorm. SDHA, YWHAZ and HPRT still occupy the highest positions in control animals, with stability values of 0.068, 0.125 and 0.132, respectively; while YWHAZ, GAPDH and SDHA shows the highest stability values in disease-stressed sheep (ρ values = 0.046, 0.064 and 0.188, respectively). When expression data from control and disease-stressed animals were combined, the resulting ranking confirmed SDHA and YWHAZ in the top positions with stability values of 0.093 and 0.096, respectively, followed by ACTB (ρ value = 0.099). TFRC and PGK1 are equally defined as the least reliable controls by both software and in all sheep groups. 