Myostatin is an extracellular negative regulator of muscle growth. It is a member of the growth factor family TGF‑β, having similar structural and functional characteristics. Based on these structural and functional characteristics we have designed several gene constructions in order to create a series of dominant negative alleles of murine myostatin. Our aim is to obtain double‑muscled calves in the first generation by mating a modified sire carrying a dominant negative allele with non‑modified cows.