Restrepo Betancur, GiovanniGiraldo Giraldo, John JairoGómez Oquendo, JorgeVásquez Araque, NeilVásquez Correa, Eliana MaríaOrtega Flórez, Jorge AndrésCórdoba, Luís Fernando2011-06-032011-10-142011-06-032011-10-142011-06-03978-958-8406-12-1http://hdl.handle.net/10567/71Abastract: Introduction. The production of embryos in horses is a technique that provides higher reproduction efficiency for animals with a high genetic value. The access to it and its success are limited, though, due to the difficulties to reach efficient fertilization rates by the use of in vitro conventional fertilization, and given the need of many technical and economic resources for ICSI (intracytoplasmic sperm injection), among other limitations for embryo development in vitro. A fundamental step for embryo production in horses is the in vitro maturation, because it determines the capability an egg has to become an embryo. Several media, fluids and molecules have been evaluated, aiming to improve this process, but an optimal composition of the maturation medium for horse oocytes is not yet known. Objective. To evaluate two components for in vitro maturation: The bovine fetal serum and the horse’s follicular fluid, to understand the physiological reproductive conditions of mares in our environment and what component is better for the maturation as an indicator of the oocyte´s ability to develop itself as an embryo. Materials y Methods. For the in vitro maturation, the bovine fetal serum and the horse´s follicular fluid, they were individually included in a 20% proportion in TCM-199 medium, additionally supplemented with gonadotropins (FSH and LH), antibiotics, glutamine, insulin, transferrin and selenium. Groups of 5 oocytes were incubated during a 36 hours period in controlled environmental conditions, at 39°C, 5% of CO2 and 90% of relative humidity. Results. Higher percentages of maximum expansion of the cluster could be seen for oocytes supple mented with bovine fetal serum (47.5%) compared with those maturated with horse’s follicular fluid (16,2%). No statistic difference was found for the in vitro maturation percentages between treatments. Conclusion. The bovine fetal serum as a supplement for in vitro maturation has a beneficial effect on the cluster expansion of horse’s oocytes.esCaballos - InseminaciónCaballos - Mejoramiento de la especieReproducción animalTransferencia de embrionesFecundación in vitroInseminación artificial - TecnologíaBiotecnología reproductivaCorporación Universitaria LasallistaBook chapter