Theses and Dissertations

Issuing Body

Mississippi State University

Advisor

Larson, Jamie

Committee Member

Lemley, Caleb O.

Committee Member

Feugang, Jean M.N.

Committee Member

Block, Jeremy

Date of Degree

8-12-2016

Document Type

Dissertation - Open Access

Major

Life Sciences

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Agriculture and Life Sciences

Department

Department of Animal and Dairy Sciences

Abstract

Ovarian steroids assist in the development of the follicle and its enclosed oocyte as well as prepare the maternal environment for pregnancy. The objective of experiment 1 was to elucidate the differences between dominant follicles of each follicular wave in terms of intraollicular concentration of steroids after 4 d of dominance. Differences in blood perfusion between the dominant follicle of the first and second non-ovulatory wave were also examined. Follicular waves were monitored daily via ultrasonography from emergence to aspiration of the dominant follicle. It was determined that although the dominant follicles aspirated from ovulatory waves possessed a greater concentration of estradiol and a greater ratio of estradiol to progesterone, there was no difference in concentrations of steroid hormones or the ratio of estradiol to progesterone between dominant follicles collected from non-ovulatory waves and ovulatory waves. In a subset of cows, blood perfusion tended to be greater in dominant follicles that developed during the second non-ovulatory wave. The objective of experiment 2 was to determine whether or not the follicular wave had an effect on diameter of the ovulatory follicle, thickness of the endometrium, or subsequent pregnancy rates. Estrus was synchronized in females in such a way that females would ovulate the dominant follicle of the first or second follicular wave at timed artificial insemination. Diameter of the ovulatory follicle and endometrial thickness were not different between treatments; however, increased pregnancy rates were observed in heifers that ovulated the dominant follicle of the second follicular wave. There was no effect of follicular wave on pregnancy rates in cows. In conclusion, the role of follicular wave on the dominant follicle, maternal environment, and subsequent pregnancy rates is not fully understood. Additional experiments need to be conducted to further elucidate the differences in developmental potential of the oocyte and maternal environment when the dominant follicle of the first and second wave are destined to become the ovulatory follicle at timed insemination.

URI

https://hdl.handle.net/11668/19889

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