Influence of heparin or the presence of cumulus cells during fertilization on the in vitro production of goat embryos

Abstract

Considerable research has been focused on in vitro production (IVP) of goat embryos to improve its efficiency. In Experiment 1, the effect of the cumulus cells by comparing slaughterhouse-oocytes denuded on purpose (DOP) prior to IVF to intact COC, and the effect of heparin during IVF were assessed. In Experiment 2, oocytes that were already denuded at collection (DOC), DOP and intact COC were studied. Three treatments used oocytes denuded at collection: DOC oocytes were cultured alone for both IVM and IVF; DOC and COC were cultured together for both IVM and IVF or DOC were IVM alone and then mixed with COC for IVF. In other treatments, COC were allocated to four IVF treatments: Intact COC; COC were denuded prior to IVF; COC were denuded and IVF with added cumulus cells; COC were denuded and IVF mixed with intact COC giving two sub-treatments: Denuded oocytes that were IVF with COC; and COC that were IVF with denuded oocytes. After fertilization, all presumptive zygotes were cultured for 8 days. In Experiment 1, the yield of blastocysts as a proportion of total oocytes was greater (P<0.05) for COC that were IVF in the presence of heparin (54%) than without heparin (42%) or oocytes already denuded at collection that were IVF with or without heparin (41%; 38%; respectively). In Experiment 2, the developmental potential of oocytes denuded at collection was reduced (cleavage and blastocyst rates calculated from total oocytes: 34%; 11%, respectively) as compared to COC (77%; 59%, P<0.05). However, when equal numbers of both were mixed at the start of IVM, the rates were not significantly different to COC alone (68%; 45%), but when both were mixed equally only for IVF, the rates were reduced (57%; 40%, P<0.05). Denuded oocytes co-cultured with cumulus cells were not significantly different to intact COC (76%; 55%). The effect of adding COC during IVF to oocytes denuded after IVM was similar to adding cumulus cells to the same type of oocytes. In conclusion, both the use of heparin and the association of oocytes with cumulus cells, either detached or in intimate contact, during IVM and/or IVF significantly improve IVP of goat embryos. Furthermore, some oocytes that are already denuded at collection will develop satisfactorily to blastocysts when matured and fertilized with intact COC.