Corpus luteum function after repeated follicular phases in ewes
Abstract
The objectives of this study were to determine if electrocautery (EC) of preovulatory follicles altered subsequent follicular recruitment and corpus luteum (CL) function. Sixty-nine ewes were assigned randomly to a 3 x 2 factorial design. Treatments consisted of 3 EC episodes (0, 1 or 2) and 2 ovariectomy (OVX) treatments (none or 12 days after the final EC episode). Initial surgery for each ewe was performed 12 to 18 hours after the onset of estrus. Ovaries were exteriorized through a midventral incision while ewes were on inhalation anesthesia. At EC, all preovulatory follicles were measured and then destroyed. Ewes assigned to 0 EC underwent surgery but no follicles were destroyed. Surgeries were performed at 3.5 day intervals for ewes requiring 2 EC episodes. Ewes OVX 12 days after EC had CL present which were harvested and weighed. Ewes not OVX were observed at 4-hour intervals for return to estrus. Blood samples were collected every 12 hours beginning 48 hours prior to expected estrus and continued until 120 hours after the final EC episode. Daily blood samples were then collected until OVX or return to estrus. Peak height of successive LH surges were less than 50% of original values after one and two EC episodes. Within the 2 EC group, concentrations of FSH were higher after the second LH surge than concentrations during the same period after first and third LH surges. The number of follicles increased from first to second EC within the 2 EC group. However, size of the largest follicle electrocauterized did not change from 1 EC to 2 EC. Estrous cycle length was decreased (P $<$.01) after 1 and 2 EC episodes (15.6 $\pm$.3 and 15.4 $\pm$.3 days, respectively) compared to 0 EC episodes (16.8 $\pm$.2 days). Number of CL present at OVX was 2.4 $\pm$.3, 2.8 $\pm$.3 and 2.9 $\pm$.3 for 0, 1 and 2 EC episodes, respectively. Similarly, total CL weight did not differ among EC treatments and averaged 1,499 $\pm$ 143 mg. Serum concentrations of progesterone (P4) during the subsequent luteal phase were similar after 0, 1 and 2 EC episodes, respectively. In summary, successive follicular phases, without intervening luteal phases, did not alter subsequent ovulation rate, total CL weight or serum concentrations of P4. However, concentrations of LH and FSH were influenced after 1 and 2 EC episodes. In conclusion, follicles recruited following EC ovulated and formed normal CL in the face of different hormonal environments.
Degree
Ph.D.
Advisors
Allrich, Purdue University.
Subject Area
Anatomy & physiology|Animals
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