[EN] The ageing process after animal slaughter enhances tenderness and influences the value of meat. Horse meat is becoming more popular but lacks standardized ageing practices that should be supported by a better understanding of post-mortem muscle biochemistry. Steaks from Longissimus Thoracis et Lumborum (LTL) of eight Hispano-Bret ' on horses were aged for 0, 7, 14 and 21 days and myofibrillar proteins were resolved by one dimensional gel electrophoresis (1-DE). Ten protein bands were found to change (p < 0.05) among ageing periods. Most changes were observed between days 0 and 14, suggesting that tenderization occurred primary during the first two weeks. Liquid isoelectric focusing (OFFGEL) technology was applied to better resolve myofibrillar sub-proteome and evidenced fourteen protein bands that changed (p < 0.05) between 0 and 21 days. Three of them were protein fragments coming from troponins T and I and from creatine kinase. Identified molecules could be further studied as potential markers for horse meat tenderness.