USING HORMONE-TREATED PREGNANT COWS AS A POTENTIAL SOURCE OF OOCYTES FOR IN-VITRO FERTILIZATION

In vivo collection of oocytes during pregnancy may be an alternative m ethod of obtaining gametes for in vitro fertilization (IVF) from genet ically superior gestating cattle. The objectives of this experiment we re to induce follicular growth in mature beef cows during each trimest er of pregnancy, and then to collect oocytes and verify oocyte compete ncy by IVF and subsequent embryo culture in vitro. Cyclic beef cows in Treatment A and pregnant cows in Treatment B were administered a tota l 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 administ ered 25 mg of PGF(2) alpha 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(2) alpha and served as a control gro up. Following a gonadotropin treatment, the ovaries of each female wer e evaluated for follicular development by ultrasonography. Oocytes wer e collected by follicle aspiration from cows in the first trimester. F ollowing IVF procedures, the embryos were co-cultured on caprine ovidu ctal 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 h ours after FSH treatment was not different for cows in Treatments A. a nd 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 coll ected in vivo and exposed to IVF, resulted in 20% cleaving, and of the se embryos 50% developed to the morula stage in culture. In summary, s timulating supplemental follicular development with FSH treatment duri ng pregnancy and collecting the oocytes for IVF may be an alternative method for obtaining supplemental gametes from valuable donor cattle.