Oocyte production in the early postpartum cow

Abstract

The postpartum period has been the focus of numerous studies; however, there is no information available relating to oocyte production in early postpartum cows. Ovaries of early postpartum cows were stimulated with FSH to produce follicular development and oocytes. The objectives of these studies were: (1) to evaluate the use of FSH for oocyte production in early postpartum beef cows, (2) to evaluate follicular response and oocyte quality of beef cows treated with FSH shortly after calving, (3) to evaluate FSH for oocyte production in early postpartum dairy cows, (4) to evaluate responses of FSH-treated, early postpartum beef cows in a transvaginal ultrasound-guided oocyte aspiration (TUGA) experiment using polyvinylpyrrolidone as the vehicle for FSH in a single dose plus energy supplementation and/or bovine somatotropin treatment, and (5) to evaluate if a single dose of GnRH could modify LH secretion in beef cows at day 5 and day 30 postpartum. In each of 4 experiments, TUGA was used to harvest oocytes from the FSH-stimulated donor cow ovaries. It was demonstrated that early postpartum cows did respond to exogenous FSH treatment with good follicular development and produced quality oocytes shortly after parturition. Harvested oocytes were subjected to IVF procedures. The number of follicles (>5 mm) aspirated, number of oocytes, recovery rate, number that cleaved, number of blastocysts developing from cleaved embryos, and blastocyst production rate per donor was: 19.4, 8.8, 64%, 4.3, 1.4 and 32.3%, respectively, for cows treated with FSH and oocytes harvested between day 5 and 20 postpartum. The number of follicles aspirated per donor at day 25 and 35 postpartum was 20.4 for the FSH-treated group, resulting in 12.9 oocytes (recovery rate, 63%). It was determined that a single FSH injection could stimulate the ovaries of the early postpartum cow as early as day 10 postpartum with a follicular response of 17.5 follicles and 11 oocytes recovered per cow (recovery rate, 69%). Furthermore, live calves were obtained from harvested oocytes from FSH-treated cows in the early postpartum period. In summary, TUGA should be considered as an alternative tool for obtaining oocytes for embryo production from early postpartum cows.