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Regulation of Ovarian Follicular Development with Estradiol in Cattle

Burke, Christopher R
http://rave.ohiolink.edu/etdc/view?acc_num=osu1054666226

Abstract Details

2003, Doctor of Philosophy, Ohio State University, Animal Science.
Fundamental aspects of the use of estradiol benzoate (EB) to regulate ovarian follicular development were investigated in cattle. Three experiments examined the impact of stage of follicular maturity on the ability of EB to induce estrus, ovulation and normal luteal function in prepubertal heifers, estrous cycling heifers and anestrous cows. The negative consequences of attempting to synchronize estrus/ovulation without regulating follicular development were clearly demonstrated in anestrous cows. The presence of an immature follicle at the time of applying an ovulatory stimulus, resulted in estrus without ovulation, or decreased function of the subsequently formed corpus luteum if ovulation did occur. This sensitivity was not apparent in heifers. Another three experiments examined histological and functional changes associated with EB-induced atresia in the dominant follicle (DF). A rapid and sustained loss in the capacity of the DF to produce estradiol was promoted by treatment with EB. These effects were associated with decreased circulating concentrations of LH or FSH. A primary target for this atretogenic action was aromatase. The DF of EB treated heifers had fewer granulosa cells, although no differences were observed in the rate of apoptosis or expression of apoptotic triggers (Fas/FasL). This approach could serve as a useful model to further investigate the process of ovarian follicular atresia. The final experiment examined the DF-independent action of EB in regulating the timing of new follicular development by aspirating the DF on the ovaries of cows and then administering various doses of EB. Timing of follicular emergence and the rise in FSH that precedes emergence were delayed in a dose dependent manner. Clearance of estradiol from circulation to allow for a rise in FSH was a key factor in determining the timing of new follicular development. These studies demonstrate that follicular development needs to be regulated to successfully synchronize estrus/ovulation. Induction of atresia in the DF is rapidly achieved at the cellular and molecular levels; therefore, the variation in timing of new follicular development is dependent on clearance of estradiol from circulation. Further studies should aim at developing an approach where this pre-emergence rise in FSH is more tightly regulated.
Michael Day (Advisor)
Biology, Animal Physiology
Bovine; Ovary; Follicle development; Steroid hormone; Estradiol Benzoate

Recommended Citations

Citations

  • Burke, C. R. (2003). Regulation of Ovarian Follicular Development with Estradiol in Cattle [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1054666226

    APA Style (7th edition)

  • Burke, Christopher. Regulation of Ovarian Follicular Development with Estradiol in Cattle. 2003. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1054666226.

    MLA Style (8th edition)

  • Burke, Christopher. "Regulation of Ovarian Follicular Development with Estradiol in Cattle." Doctoral dissertation, Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1054666226

    Chicago Manual of Style (17th edition)

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This open access ETD is published by The Ohio State University and OhioLINK.