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Influence of the Size and Age of the Ovulatory Follicle on Fertility in Beef Cattle

Mussard, Martin Lane
http://rave.ohiolink.edu/etdc/view?acc_num=osu1259810767

Abstract Details

2009, Doctor of Philosophy, Ohio State University, Animal Sciences.
Artificial insemination (AI) is an underutilized technology in the beef industry. Four experiments were performed to improve understanding of the reproductive system of cattle and how this information can be incorporated into estrous control programs to advance the use of AI in the beef industry. In the first experiment, cows were permitted to either spontaneously exhibit estrus and ovulate from a dominant follicle, or were induced to ovulate from a dominant follicle when it had reached 10 mm in diameter; which is considered smaller than the diameter at which ovulation normally occurs (13-15 mm). This model allowed corpus luteum (CL) function and fertility to be measured in animals that ovulated from dominant follicles differing in diameter and that matured within two different endocrine environments. Conception rate to artificial insemination (AI) was greater in those animals that ovulated from a follicle following spontaneous estrus as compared with animals that ovulated from a smaller dominant follicle in response to treatment with exogenous GnRH. Results from this experiment were the basis for the second experiment designed to examine differences in luteal function and fertility between cows induced with exogenous GnRH to ovulate from either small or large dominant follicles. This approach eliminated the confounding effect that occurrence of spontaneous estrus may have exerted on fertility. Animals that ovulated from a large follicle in response to exogenous GnRH were more fertile than those animals induced to ovulate from a smaller follicle. The third experiment was designed to begin to elucidate mechanisms responsible for reduction in fertility in cows induced to ovulate from small follicles. Embryos from untreated donors were implanted into animals that were treated in a similar fashion as in the second experiment, but not inseminated preceding ovulation. This approach allowed separation of effects of the ovum, uterus and luteal function on fertility. Fertility was decreased in cows that had previously ovulated from a small follicle, as compared to those induced to ovulate from larger follicles when embryo transfer was used to impregnate the cows. The final experiment was performed to determine if decreased fertility observed in the previous experiments was due to size of the follicle from which ovulation occurred or duration of proestrus. In previous experiments the interval from luteal regression to induction of ovulation was confounded with diameter of the follicle from which ovulation was induced to occur. Hence, this experiment was essential to identify whether follicle diameter or duration of proestrus was having the greater impact on fertility. Fertility was dependent on length of proestrus when ovulation from follicles of similar diameter was induced. Taken together, results of the experiments described in this dissertation provide evidence that fertility is significantly influenced by duration of proestrus. Information garnered from these experiments can readily be incorporated into future estrous cycle regulation programs and superovulation regimens for embryo transfer.
Michael Day, Dr. (Advisor)
James Kinder, Dr. (Committee Member)
Steven Loerch, Dr. (Committee Member)
Joy Pate, Dr. (Committee Member)
Charles Looney, Dr. (Committee Member)
106 p.
Animals
Cattle; Follicle; Ovulatory Follicle; Size; Age; Fertility

Recommended Citations

Citations

  • Mussard, M. L. (2009). Influence of the Size and Age of the Ovulatory Follicle on Fertility in Beef Cattle [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259810767

    APA Style (7th edition)

  • Mussard, Martin. Influence of the Size and Age of the Ovulatory Follicle on Fertility in Beef Cattle. 2009. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1259810767.

    MLA Style (8th edition)

  • Mussard, Martin. "Influence of the Size and Age of the Ovulatory Follicle on Fertility in Beef Cattle." Doctoral dissertation, Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259810767

    Chicago Manual of Style (17th edition)

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