Thyroid hormone-inducible hepatic protein is involved in the de novo synthesis of fatty acids in the lactating mammary gland. Different variants of the gene that encodes this protein may be associated with its different activity. The primary aim of this study was to find polymorphism in the THRSP gene and estimate the relationship between individual genotypes and fatty acid composition in milk. Investigations were carried out on 224 cows represented by two breeds—Jersey (n = 80) and Polish Holstein-Friesian (n = 144). Polymorphism in THRSP was detected by Sanger sequencing; however, genotypes were determined by the PCR-RFLP method. It was shown that the analyzed variant had a significant (p THRSP gene (rs42714482) may be considered as a potential marker for fatty acid composition in milk
