EN
The aim of the study was to determine and evaluate the relationships between the susceptibility of Kołuda sheep to mastitis and the presence of polymorphic forms of haemoglobin (HBB) and transferrin (TF) in their blood. Udder health was evaluated twice during lactation by udder palpation and using milk tests for electric resistance, somatic cell count per cm³ and microbiological analysis for the presence of etiological factors of mastitis. The analysis of haemoglobin and transferrin polymorphism in the population of 231 Kołuda sheep showed the presence of 2 alleles at the HBB locus and 6 alleles at the TF locus, which determine the presence of 3 and 15 genotypes of these proteins respectively. The correlations between the presence of the genotypes (as well as the alleles that determine them) and udder health were analysed statistically using the chi-square (χ²) test. None of the alleles at the HBB locus showed statistical correlations with the incidence of mastitis. The results obtained show that the two alleles of TFᴬ and TFᴾ transferrin can be taken to indicate the susceptibility of Kołuda sheep to mastitis and could be used in genetic selection to improve udder health in Kołuda sheep.