© 2022 Namik Kemal University - Agricultural Faculty. All rights reserved.The study aimed to determine the MSTN gene variation in 90 donkeys reared in the Thrace region of Turkey. Myostatin (MSTN), also named GDF-8 (growth differentiation factor 8) is a part of the transforming growth factor β (TGF-β) superfamily and it has a negative regulator role on muscle mass, growth and development in mammalian species. MSTN gene regulates the skeletal muscle growth in a negative way and has a significant role in homeostasis of skeletal muscles. Also, in muscle fibers balance of protein has been promoted by Myostatin factor. The total of 866 bp long partial intron 1 and 2, whole exon 2 regions of MSTN gene was amplified and PCR products analysed using DNA sequencing. In this study, a novel synonymous SNP was determined as g.4183919 G>A in the second exon region of the MSTN gene which does not cause an amino acid change in the protein. The G>A transition caused a silent mutation in leucine (leu) amino acid. Alterations in mRNA level and functionality of protein can occur due to synonymous mutations. Since leucine is an important amino acid that can avoid muscle mass loss and inhibits the expression of Myostatin, it can be said that silent mutation of Leu in donkeys may have altered the muscle mass and physical factor of donkeys in this study. Mutant leucine may have a lower efficient effect on preventing loss of muscles and causes more Myostatin protein expression. The identified SNP was firstly released and the DNA sequences of the MSTN gene in Turkish donkeys was revealed for the first time with recent study. Turkish donkeys lacked these mutations that were identified before in horses, which cause for the less might require for race ability of donkeys. The sequences of MSTN gene were submitted to the NCBI GenBank with the accession number: MW970078- MW970079. Further studies are needed to conduct, on protein and molecular levels, SNPs on the MSTN gene and their association with the morphological characters that may affect economic traits in donkey breeds.