Ovary fragments from six sexually mature cats were vitrified in the presence or absence of betaine or ascorbic acid, loaded (7.4 or 74µM betaine; 20 or 200µM ascorbic acid) or not (1mM betaine or 0.3mM ascorbic acid) into CaCO3 microparticles, and assessed for follicular morphology, oxidative stress and mitochondrial activity Feline ovarian tissue was successfully preserved after vitrification in the presence of 74µM betaine loaded in CaCO3 microparticles, as confirmed by morphological analysis and the density of preantral follicles and stromal cells, as well as by the increased mitochondrial activity and decreased production of reactive oxygen species.