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Most of the Western European cattle breeds consist of standardised breeds with a definite coat colour (Renieri et al., 1984). Thus coat colour could be useful to detect genetic markers for cattle breed identification. In cattle the pigmentation is determined by the distribution of two pigments: eu- and pheomelanin, producing brown or black and red to yellow pigmentation respectively. Tyrosinase, the rate-limiting enzyme involved in the synthesis of both melanins, is regulated by the melanocyte stimulating hormone (αMSH). This hormone and several other melanotropic peptides stimulate melanin formation in melanocytes by binding to the melanocortin-1-receptor (MC1R), a G-protein-coupled receptor encoded by the Extension gene (Robbins et al., 1993). In addition, the amounts of eu- and pheomelanin in the melanocyte are controlled by the agouti gene encoding the Agouti Signal Protein (ASP), that acts as an antagonist of MSH signalling through the MC1R, even if its mechanism of action is controversial (Furumura et al., 1998)..........