Recovery and fertilization of bovine follicular oocytes

Infertility in many valuable cows could be overcome by transferring ovarian oocytes to host animals for fertilization. Oocytes were recovered from 134 cows stimulated with gonadotropin. Ovulations occurred as early as 12 hr after first observance of estrus and by 24 hr ovulations were present in 73% of the donors. With 2000 IU PMSG donors averaged 19.4 visible follicles from which oocytes were recovered 60% of the time. Large doses of gonadotropin produced more visible follicles (mean of 52.9) but a low recovery rate of oocytes (32%) and a lower incidence of maturation within the oocytes (20%). Fertilization depended on the condition of the oocytes and the ease of transfer to the oviducts of hosts. Using this technique to obtain large numbers of embryos necessitates treatments either to render immature oocytes fertile or to obtain large numbers of mature follicular oocytes.