Claes Anthony, Ball Barry A, Scoggin Kirsten E, Roser Janet F, Woodward Elizabeth M, Davolli Gabriel M, Squires Edward L, Troedsson Mats H T
Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA.
Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington, KY, 40546-0099, USA.
Theriogenology. 2017 Jul 15;97:34-40. doi: 10.1016/j.theriogenology.2017.04.019. Epub 2017 Apr 13.
Reproductive aging must be well understood to optimize the reproductive management of older mares and to predict their reproductive life-span. The objectives of this study were to: 1) examine age-related differences in follicular dynamics, endocrine profiles, and primordial follicle counts, 2) evaluate the influence of antral follicle count (AFC) on age-related changes in follicular parameters, and 3) determine the influence of diestrous ovulations on the estrous cycle. Young (3-8yr; n = 10), middle-aged (9-18 yr; n = 16), and old (>18 yr; n = 19) light horse mares were examined with transrectal ultrasonography to monitor follicular growth over two consecutive estrous cycles. Jugular blood samples were taken and plasma progesterone and FSH concentrations were determined by an enzyme immunoassay and radioimmunoassay, respectively. Both interovulatory intervals and follicular phases were longer and the day of follicle deviation occurred later in aged mares. Furthermore, older mares had a tendency to ovulate smaller follicles. Neither follicular growth rate, the number of ovulations nor the length of luteal phase was influenced by mare age. Interestingly, as mare age increased, mares with low AFC had longer interovulatory intervals and follicular phases than mares with medium or high AFC. In addition, the number of primordial follicles declined with an increase in mare age but varied considerably between mares of the same age. Progesterone concentrations were positively influenced by age, whereas FSH concentrations were not, despite that FSH concentrations appeared higher in aged mares during the follicular phase. Estrous cycles with a diestrous ovulation had a longer interovulatory interval as well as a longer follicular and luteal phase while day of deviation occurred later. Progesterone concentrations were significantly higher on day 14 and 16 in estrous cycles with a diestrous ovulation than without a diestrous ovulation. In conclusion, aging in mares is associated with changes in follicular parameters which in turn are closely linked to differences in antral follicle count suggesting a relationship with ovarian reserve. Therefore, determination of antral follicle counts in aged mares can provide valuable information about the reproductive aging process. Finally, diestrous ovulations have a significant influence on different estrous cycle parameters.
为了优化老龄母马的繁殖管理并预测其繁殖寿命，必须充分了解生殖衰老。本研究的目的是：1）研究卵泡动态、内分泌特征和原始卵泡数量的年龄相关差异；2）评估窦状卵泡计数（AFC）对卵泡参数年龄相关变化的影响；3）确定间情期排卵对发情周期的影响。对年轻（3 - 8岁；n = 10）、中年（9 - 18岁；n = 16）和老龄（>18岁；n = 19）轻型母马进行经直肠超声检查，以监测连续两个发情周期的卵泡生长情况。采集颈静脉血样，分别通过酶免疫测定法和放射免疫测定法测定血浆孕酮和促卵泡素（FSH）浓度。老龄母马的排卵间期和卵泡期均较长，卵泡偏离日出现较晚。此外，老龄母马倾向于排出较小的卵泡。母马年龄对卵泡生长速度、排卵次数和黄体期长度均无影响。有趣的是，随着母马年龄增加，AFC低的母马比AFC中等或高的母马排卵间期和卵泡期更长。此外，原始卵泡数量随母马年龄增加而减少，但同龄母马之间差异很大。孕酮浓度受年龄的正向影响，而FSH浓度不受年龄影响，尽管老龄母马在卵泡期FSH浓度似乎更高。有间情期排卵的发情周期排卵间期、卵泡期和黄体期均较长，卵泡偏离日出现较晚。有间情期排卵的发情周期第14天和第16天的孕酮浓度显著高于无间情期排卵的发情周期。总之，母马衰老与卵泡参数变化有关，而卵泡参数变化又与窦状卵泡计数差异密切相关，提示与卵巢储备有关。因此，测定老龄母马的窦状卵泡计数可为生殖衰老过程提供有价值的信息。最后，间情期排卵对不同发情周期参数有显著影响。
