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Ovarian and endocrine dynamics associated with sexual maturation in beef heifers and the influence of diet, weaning age, and other factors during early reproductive development

Gasser, Chad L
http://rave.ohiolink.edu/etdc/view?acc_num=osu1122295880

Abstract Details

2005, Doctor of Philosophy, Ohio State University, Animal Science.
A series of experiments was designed to test the ability to induce precocious puberty in heifers and to determine the underlying mechanisms responsible for the precocious attainment of puberty. A model consisting of early weaning (3-4 months of age) and feeding a high-concentrate diet was used for each experiment. This method resulted in increased body weight gain. Additionally, precocious puberty was induced in a vast majority of heifers; and consequently, mean age at puberty was substantially reduced. Heifers that achieved precocious puberty did so at lesser body weights. In addition, subsequent estrous cycles continued after precocious attainment of puberty. In the first experiment, heifers that were weaned early and fed the high-concentrate diet exhibited a greater frequency of LH pulses leading to precocious attainment of puberty. In the second experiment, ovarian maturation was accelerated during the same period leading up to puberty. This was evidenced by increased maximum diameter of dominant ovarian follicles, increased duration of waves of ovarian follicular development, and increased peak estradiol concentrations during follicle waves. In the third experiment, estradiol-implanted, ovariectomized heifers that were weaned early and fed the high-concentrate diet escaped from estradiol negative feedback on LH secretion at a younger age, which was similar to the age at which ovary-intact heifers on the same diet attained puberty. It was concluded from these results that advancement of the decline in estradiol negative feedback on secretion of LH is the mechanism by which early weaning and feeding a high-concentrate diet induces precocious puberty in heifers. Essentially, the peripubertal period of development in heifers was shifted to a younger age with this model. A fourth experiment was conducted to determine the relative effects of timing of feeding the high-concentrate diet on age at puberty in early-weaned heifers. It was discovered that feeding the high-concentrate diet only for a period of 10 weeks after early weaning successfully advanced puberty to an extent similar to that of continuous feeding of the high-concentrate diet after early weaning. These experiments provide evidence that nutritional control during the early maturational period in heifers exerts substantial influence on timing of puberty.
Michael Day (Advisor)
Puberty; Heifer; Ovarian Follicular Development; Early Weaning; Precocious Puberty

Recommended Citations

Citations

  • Gasser, C. L. (2005). Ovarian and endocrine dynamics associated with sexual maturation in beef heifers and the influence of diet, weaning age, and other factors during early reproductive development [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1122295880

    APA Style (7th edition)

  • Gasser, Chad. Ovarian and endocrine dynamics associated with sexual maturation in beef heifers and the influence of diet, weaning age, and other factors during early reproductive development. 2005. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1122295880.

    MLA Style (8th edition)

  • Gasser, Chad. "Ovarian and endocrine dynamics associated with sexual maturation in beef heifers and the influence of diet, weaning age, and other factors during early reproductive development." Doctoral dissertation, Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1122295880

    Chicago Manual of Style (17th edition)

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© 2005, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.