Forty Nellore heifers were fed (73days) with different diets: with or without essential oils (clove and/or rosemary essential oil) and/or active principle blend (eugenol, thymol and vanillin). The pH, fat thickness, marbling, muscle area and water losses (thawing and drip) were evaluated 24h post mortem on the Longissimus thoracis, and the effects of aging (14days) was evaluated on the meat cooking losses, color, texture and lipid oxidation. Antioxidant activity was also evaluated. Treatments had no effect (P>0.05) on pH, fat thickness, marbling, muscle area, thawing and drip losses. However, treatments affected (P<0.05) cooking losses, color, texture and lipid oxidation. The diets with essential oil and the active principle blend reduced the lipid oxidation and reduced the color losses in relation to control diet. Aging affected (P<0.05) texture and lipid oxidation. The essential oil and active principles or its blend have potential use in animal feed aiming to maintain/improve meat quality during shelf-life
