Received: 17 June 2019 Accepted for publication: 10 January 2020 Slov Vet Res 2020: 57 (1): 25 –31 DOI 10.26873/SVR-914-2020 UDC 636.2.09:57.083.3:591.151:575.117 Original Research Article Introduction As an effect of antagonistic genetic correlations between milk yield and immunity, a decline in resistance to disease has been observed in highly productive herds (1, 2). The goal of high proftability has complicated the issue of selecting the most appropriate method for production as well as fertility management, udder health, and resistance to disease while maximising proft without compromising animal welfare. Recent INVESTIGATION OF G+265C AND G-1539A SINGLE NUCLEOTIDE POLYMORPHISMS OF TOLL-LIKE RECEPTOR 4 GENE (TLR4) IN SOME CATTLE BREEDS RAISED IN TURKEY Özgecan Korkmaz Ağaoğlu 1 *, Bilal Akyüz 2 , Emel Zeytünlü 3 , Ali Reha Ağaoğlu 4 1 Department of Animal Science, 4 Department of Obstetrics and Gynecology, Faculty of Veterinary Medicine, Burdur Mehmet Akif Ersoy University, Burdur, 15030, 3 Department of Animal Science, Institute of Health Sciences Burdur Mehmet Akif Ersoy University, Burdur, 15030, 2 Department of Genetics, Faculty of Veterinary Medicine, Erciyes University, Kayseri, 38039, Turkey *Corresponding author, E-mail: ozgecanagaoglu@mehmetakif.edu.tr Abstract: Toll-like receptors play an essential role in how the innate immune system reacts to pathogens. These receptors help the innate immune system recognise the antigenic structure of pathogens and initiate the inflammatory response. TLR4 is one of these receptors, and it has been identified as a candidate molecular marker for resistance to mastitis in cattle. This study aimed to describe G-1539A (BgII) in promoter and G+265C (MspI) in 5’-UTR polymorphisms in the TLR4 gene using Zavot (n=60), East Anatolian Red (EAR, n=49), Anatolian Black (AB, n=59), South Anatolian Red (SAR, n=42), Turkish Gray (TG, n=60) and Holstein (n=218) cattle breeds. For this purpose, we used polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) to genotype a total of 488 cattle. Two alleles (A and G) and three genotypes (GG, GA and AA) were examined by digestion of the PCR product with BgII restriction enzyme. The frequency of the G allele was higher in all investigated breeds except Zavot. The GA genotype was found to be the most common genotype in the EAR, SAR, TG, AB, Holstein, and Zavot breeds. Two alleles (C and G) and three genotypes (GG, GC and CC) were examined by digestion of the PCR product for the G+265C SNP with the MspI restriction enzyme. The most prevalent in terms of frequency was the C allele in all breeds with regard to G+265C SNP. All examined breeds were within the Hardy-Weinberg equilibrium (p>0.05). Consequently, the existence of two SNPs of the TLR4 gene has been reported for the first time in six cattle breeds raised in Turkey. The study demonstrated that the investigated breeds continue to exhibit variation in terms of these two SNPs. It might be possible to utilise these polymorphisms in efforts to breed herds resistant to significant breeding diseases, such as mastitis. Key words: cattle; PCR-RFLP; promoter; SNP; TLR4 studies have shown that creating herds resistant to serious breeding diseases, such as mastitis, tuberculosis, and brucellosis, could increase the proftability of livestock enterprises (3, 4). However, creating healthy herds with genetic improvement programmes in dairy populations takes a long time. Nowadays, it is thought that some genes, such as toll-like receptor genes, could be used to increase immune resistance in livestock. In mammals, the immune system is divided into the innate and adaptive immune systems. Toll-like receptors (TLRs), an essential component of the immune system, activate innate immune reactions, which then cause adaptive immune