The aim of this study was to investigate leptin gene polymorphism in Sistani cows and brown swiss cows and relationship between it’s polymorphism with economical traits in them. Blood samples were collected from Sistani cows and Brown Swiss cows. DNA was extracted from the blood samples and then it was amplified by Polymerase Chain Reaction (PCR) technique to amplify a 422 bp DNA fragment. Digestion of amplicons with BstMB1 was done on PCR product. Genotype frequencies were 0.77, 0.22, 0.01 for AA, AB and BB, respectively in Sistani cows and 0.64, 0.35 and 0.01 for AA, AB and BB, respectively in Brown Swiss cows. The populations were in Hardy-Weinberg equilibrium with respect to Leptin gene. The AB genotype had a significant effect on growth traits including weight at 9 and 12 months and age at successful insemination than the other genotypes in Sistani cows. AB genotype also had a significant effect on milk production, days open and milking days compared with other genotypes in Brown Swiss cows.

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