Using hormone-treated pregnant cows as a potential source of oocytes for in vitro fertilization

Abstract

In vivo collection of oocytes during pregnancy may be alternative method of obtaining gametes for in vitro fertilization (IVF) from genetically superior gestating cattle. The objectives of this experiment were to induce follicular growth in mature beef cows during each trimester of pregnancy, and then to collect oocytes and verify oocyte competency by IVF and subsequent embryo culture in vitro. Cyclic beef cows in Treatment A and pregnant cows in Treatment B were administered a total dose of 40 mg of FSH in descending dose levels (6, 5, 4, 3 and 2 mg) twice daily for 5 consecutive days. Cows in Treatment A were administered 25 mg of PGF 2α and in Treatment B an equal volume of 0.9% saline at the seventh FSH injection. Pregnant cows in Treatment C were administered neither FSH nor PGF 2α and served as a control group. Following a gonadotropin treatment, the ovaries of each female were evaluated for follicular development by ultrasonography. Oocytes were collected by follicle aspiration from cows in the first trimester. Following IVF procedures, the embryos were co-cultured on caprine oviductal cells, or in the chicken embryo co-culture system, or were placed in goat oviducts in vivo. The mean number of follicles per ovary 12 hours after FSH treatment was not different for cows in Treatments A and B, (8.1 vs 7.7) and both numbers were greater (P<0.05) than the 1.1 follicles per ovary for the control cows in Treatment C. Oocytes collected in vivo and exposed to IVF, resulted in 20% cleaving, and of these embryos 50% developed to the morula stage in culture. In summary, stimulating supplemental follicular development with FSH treatment during pregnancy and collecting the oocytes for IVF may be an alternative method for obtaining supplemental gametes from valuable donor cattle.