Abstract. Several studies have clarified that the follicular cysts degenerate and are replaced by newly growing follicles that develop into new follicular cysts without ovulation, i.e., turnover of ovarian follicular cysts in cows. However, the relativity of endocrinological changes, including the inhibin profile during turnover of spontaneous follicular cysts in dairy cows, is still unclear. In the present study, the relationship between turnover of follicular cysts and changes in the peripheral blood concentrations of progesterone (P), estradiol-17β (E2), luteinizing hormone (LH), follicle stimulating hormone (FSH) and inhibin were examined in lactating dairy cows. Five cows diagnosed with follicular cysts (follicles of more than 25 mm in diameter in the absence of a corpus luteum) were investigated. Their ovarian dynamics were monitored using ultrasonography, and blood samples were collected at 2-or 3-day intervals throughout the experiment. The day when a follicle fated to become a follicular cyst reached more than 8 mm in diameter was defined as the start of a cystic follicular wave. Four of the 5 cows exhibited a similar patterns of cystic follicular changes and hormone profiles. The data from the 4 cows was used for analysis of the relationships between turnover of cystic follicles and the hormone profiles. Two or three new cystic follicular waves occurred in each cow during the experimental period. The mean diameter of the cystic follicles was more than 25 mm 13 to 15 days after the start of the cystic follicular wave, and it began to decrease 1 to 6 days before the start of the subsequent cystic follicular wave. The levels of E2 and inhibin tended to decrease for 7 to 9 days before the start of a new cystic follicular wave and to increase concomitantly with new follicular cyst growth. The levels of FSH rose for 1 to 3 days before the start of a new cystic follicular wave. The present study clarified the relationship between FSH and inhibin during turnover of spontaneous follicular cysts in dairy cows and found that it was very similar to previous results for cows. The present results suggest that an increase in FSH secretion following a reduction in inhibin secretion triggers turnover of cystic follicles in cows with spontaneous follicular cysts. Key words: Dairy cow, Estradiol-17β (E2), Follicular cyst, Follicle stimulating hormone (FSH), Inhibin (J. Reprod. Dev. 53: [987][988][989][990][991][992][993] 2007) ystic ovarian degeneration is one of the major causes of infertility. It brings about a long open period after parturition in dairy cattle, and its high incidence results in considerable economic losses
Abstract. The objective of this study was to evaluate the effects of a progesterone-releasing intravaginal device (PRID) containing an estradiol benzoate capsule on ovarian dysfunction, including ovarian quiescence, follicular cyst (FC) and luteal cyst or cystic corpus luteum (LC/CCL), in postpartum dairy cows. These ovarian dysfunctions were examined by palpation per rectum relative to plasma progesterone status. The results of clinical examination and hormone assay determined ovarian quiescence in 13 cows, FC in 15 cows and LC/CCL in 7 cows. These cows were treated with PRID for 12 d and then clinical examination was performed. After PRID removal, the proportion of cows exhibiting estrous signs within 7 d and confirmed formation of CL within 7-14 d (markedly effective) were 69.2 % (n=9) for ovarian quiescence, 46.7 % (n=7) for FC, and 28.6 % (2 cows) for LC/ CCL. Two cows (15.4 %) in ovarian quiescence, 5 cows (33.3%) with FC and 4 cows (57.1 %) with LC/ CCL did not exhibit estrous signs but were recognized as having formed CL within 12-16 d after removal of PRID (effective). These results suggest that treatments of PRID with estradiol benzoate for 12 d have therapeutic efficacy on ovarian dysfunction including ovarian quiescence, FC and LC/CCL in postpartum dairy cows. Key words: PRID, Ovarian quiescence, Follicular cyst, Luteal cyst or cystic corpus luteum, Dairy cow (J. Reprod. Dev. 50: [341][342][343][344][345][346][347][348] 2004) varian quiescence and ovarian cyst occur frequently during the postpartum period in dairy cows, and are serious types of ovarian dysfunction causing infertility and delay of rebreeding, resulting in economic loss to farmers [1,2]. Ovarian quiescence is confirmed by the absence of functional ovulatory follicles and luteal tissues, and blood progesterone concentrations below 1 ng/ml in the postpartum period. This condition is a ty p e o f a n e s t r u s t h a t o c c u r s d u r i n g th e postpartum period and is affected by various factors such as the season, nutrition, suckling conditions and breed [2,3]. Ovarian cysts are characterized by the persistent existence of enlarged anovulatory follicles in postpartum dairy cows. The clinical diagnosis of ovarian cyst is based on the reproductive case history, palpation via rectum of a smooth, fluid-filled structure greater than 25 mm in diameter persisting for 10 days or more, and absence of CL on the surface of the ovary [4][5][6].Some previous studies have suggested that
The aim of the present study was to clarify the ovarian and hormonal dynamics after the aspiration of follicular fluid in cows with follicular cysts. Follicular fluid was aspirated from the follicular cysts and follicles that were fated to become cystic follicles and other coexisting normal follicles, respectively, in lactating cows (n=3). After the aspiration procedure, new follicles developed and reached a diameter of 25 mm without ovulation within 13-19 days. The plasma concentrations of inhibin decreased and follicle-stimulating hormone increased rapidly after the aspiration procedure, and subsequently increased and decreased, respectively, as a new follicle grew. No luteal structures developed after the aspiration procedure, and the animals' plasma progesterone levels remained low. The present study indicates that the cystic follicles are never luteinized by the aspiration of follicular fluid, and consequently, new follicular cysts are observed to repeatedly develop.
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