In vitro-produced (IVP) bovine embryos are used in a wide range of biotechnologies but develop less well than their in vivo counterparts and can give rise to foetal/neonatal anomalies after embryo transfer. The quality of bovine IVP embryos and the systems in which they are produced are traditionally assessed in terms of morphological and developmental criteria; namely, embryo grade and blastocyst formation rate. Lane and Gardner (1996) showed that mouse embryos selected for transfer on the basis of a low glycolytic activity (conversion of glucose to lactate), measured non-invasively, were 4 times more likely to implant than those selected randomly. Comparable data are not available for bovine embryos. The aim of this study was to assess linear glycolytic index of cattle blastocysts in vitro as a marker of viability. We have measured glucose consumption and lactate production by individual bovine IVP embryos grown in cell-free conditions and in a novel co-culture system (Orsi et al., 2000) involving confluent bovine oviduct epithelial cell monolayers on permeable supports. This preparation allows the epithelial cells to be fed by a nutritionally-rich medium via the physiological, basal, route, while the apical medium, containing the embryos, is more dilute, mimicking oviduct fluid.
