| Summary: | 碩士 === 國立中興大學 === 獸醫學系 === 88 === Eight dairy cows from our NCHU farm, with a total of 16 estrous cycles were observed sonographically per rectum to determine the dynamic changes of follicles and corpus lutea (CL). The results indicated that 2-wave follicular activity appeared more often than the 3-wave pattern (81.3% vs 18.7%), with the average length of 2-wave and 3-wave cycles being 20.6 ±1.4 and 23.3 ±0.6 days, respectively (p<0.05), and the average interval of all 16 estrous cycles being 21.1 ±1.7 days. The ovulatory follicle of the 3-wave pattern differed significantly from that of the 2-wave pattern, with：(1) later emergence (Day 15.3±1.5 vs Day 9.5±3.1, p＜0.01)；and (2) shorter duration of growth (8.3 ± 2.5 vs 11.4 ± 2.5 days, p＜0.05). Uterine infusion with 100 ml 4% polycondensated m-cresolsulphuric acid-formaldehyde was performed in 20 dairy cows, which were divided into 2 groups of 10 animals per group and treated on Day 5 (Group 1) and Day 15 (Group 2) of the estrous cycle, respectively. A control group consisted of 2 cows infused with 100 ml normal saline on Day 5 and another 2 cows infused on Day 15. The results were shown as follows: (1) mean length of the estrus cycle：Group 1 was shorter than that for control group (17.4 ±1.2 vs 19.5 ± 0.7 days, p＜0.05), while the mean length of the estrous cycle for Group 2 was longer than the control group (24.0 ± 1.9 vs 21.0 ± 1.4 days, p＜0.05)；(2) follicular wave：all of the 10 interovulatory intervals of Group 1 displayed a 2-wave pattern；60% (6/10) of Group 2 showed a 3-wave pattern and the remainder showed a 2-wave pattern；(3) changes of ovarian functional structures on the ovary before the following ovulation：the CL in Group 1 began to regress on Day 11.8 ±2.3, which was earlier than the control group and cows of the former experiment (p＜0.05)；the average interval from luteal regression to ovulation in Group 2 was 9.9 ±1.9 days, which was longer than the control group and cows in the former experiment (p＜0.05). The histopathological appearance of the endometrium on Day 1 after intrauterine infusion displayed necrosis of the superficial endometrium and destruction of the glandular cells, with endometrial epithelial cells beginning to regenerate on Day 5 after infusion. Hormone analysis of dairy cows with 2- and 3-wave of follicular activity indicated that progesterone concentration increased to their highest levels on Day 10 (15.3 ±4.2n mol/L) and Day 13 (19.4n mol/L), respectively. Cows with 3-wave had FSH surges on Day 6、Day 13 and Day 17, with respectively concentrations of 2.44m IU/mL、 2.87m IU/mL and 2.59m IU/mL. The progesterone concentration in Group 1 and Group 2 declined drastically on Day 10 to Day 12 and Day 19 to Day 21, respectively.
In conclusion, the results show that cows with 2-wave patterns have a shorter interovulatory interval than cows displaying 3-wave patterns. In addition, uterine infusion with polycondensated m-cresolsulphuric acid-formaldehyde can induce regression of early functional CL and shorten the length of the estrous cycle. Although this does not delay the regression of later functional CL, it is able to prolong the interval from CL regression to ovulation, so enabling the following estrus to be delayed.
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