The objective of the research was to analyze the relationship between leptin genotypes and reproduction indices in cold blood mares. The statistical analysis was conducted on 65 mares from a stud farm in Nowe Jankowice. Based on reproductive outcomes we calculated basic reproduction indices. The leptin polymorphism was determined using the PCR-RFLP method. In the examined population, A and B allele frequencies were identical (0.50). Three genotypic forms of the leptin gene were found to occur: AB, AA, and BB. The most frequently noted form was heterozygotic AB (frequency of 0.47), whereas homozygotic AA and BB occurred with equal frequency of 0.26. The most favourable results for the majority of the other reproduction indices were observed in the AB heterozygotic mare group, whereas the least favourable in the AA mares. The said differences were not statistically significant. No significant effect of the leptin genotype on the reproduction traits in mares was found.
