RESUMO
The aim of this study was to evaluate the effect of supplementing serum-containing media with a mixture of cis- and trans-9,11- and -10,12-conjugated isomers of linoleic acid (CLA) during different steps of the in vitro production (IVM, IVC, or IVM + IVC) of bovine embryos on their embryonic development, cryotolerance, and lipid profile. To evaluate the impact of the CLA on membrane lipids, such as phosphatidylcholine (PC) and sphingomyelin (SM), the embryos' lipid profiles were obtained using matrix-assisted laser desorption ionization mass spectrometry. The cleavage rates (78.6%-84.8%) and blastocyst development (44.8%-51.2%) remained unaltered. The postthawing reexpansion rates were higher (P < 0.05) when the CLA was added to the IVM medium (82.6%) or to the IVM + IVC medium (83.8%) than the control (69.3%) or IVC medium (63.0%). Changes in the blastocysts' lipid profile occurred when supplementation was restricted to the IVM or IVC medium. However, the most prominent effects of the CLA on the embryonic PC and SM profiles were observed when the supplement was added to IVM + IVC media, which was an increase in the level of highly unsaturated PCs containing 36 or 38 carbons, which are likely to contain CLA residues. These results showed that the molecular mechanism resulting in the improved cryosurvival, observed with CLA supplementation during bovine embryonic in vitro production, was related to the composition of structural lipids of cellular membranes and is dependent on the treatment length. Monitoring the lipid profile of embryonic membranes may improve the CLA supplementation strategy and facilitate the development of new IVC systems to improve the cryopreservation of bovine embryos and those of other domestic species.