Eight cows were used to study the feasibility of transvaginal ultrasound-guided puncture of follicles as a method for the collection of immature oocytes for embryo production in vitro. In six trials at intervals of seven days, 104 oocytes were collected. After in vitro maturation and fertilisation the 104 oocytes were transferred to the oviducts of sheep. Six days later, 75 oocytes were recovered by flushing the oviducts. Twenty-four per cent of the recovered oocytes/embryos had developed into transferable and viable morulae and, or, blastocysts. The data show that this non-surgical and repeated collection of immature oocytes can be used successfully for the in vitro production of bovine embryos. The procedure may produce yields of embryos comparable to those obtainable by conventional superovulation procedures.

To investigate protein synthesis and phosphorylation during bovine oocyte maturation in vivo, oocytes were collected at consecutive times after the preovulatory luteinizing hormone (LH) peak. Therefore, heifers treated for superovulation were ovariectomized between 3 and 20 h after the maximum of the LH peak. Subsequently, cumulus-enclosed oocytes, selected from nonatretic follicles greater than 10 mm, were radiolabeled with 35S-methionine or 32P-orthophosphate for 3 h and individually prepared for gel electrophoresis. Changes in the protein synthesis patterns were observed coinciding with germinal vesicle breakdown (GVBD). No changes were detected during the ensuing maturation period or coinciding with the extrusion of the first polar body. In addition, the protein phosphorylation patterns exhibited striking differences around GVBD. In particular, a phosphoprotein band of 19 kDa and the two heavily phosphorylated proteins with apparent molecular weights between 50 and 60 kDa were present in patterns of oocytes in the germinal vesicle stage. The results are discussed in relation to previous data obtained during maturation in vitro.

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