Meyers-Brown Geraldine A, Loud Meaghan C, Hyland John C, Roser Janet F
Department of Animal Science, One Shields Ave, University of California, Davis, CA 95616, USA.
Department of Health, Population and Reproduction, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Theriogenology. 2017 Aug;98:108-115. doi: 10.1016/j.theriogenology.2017.05.001. Epub 2017 May 8.
The most common equine breeding practice to decrease the time to the first ovulation of the year is to use artificial lights starting December 1 in the Northern Hemisphere. It can take 60-90 d for this lighting regimen to induce a fertile ovulation. The success rate for pharmaceutical compounds to carry out the same process has been variable. One compound that did induce an early ovulation was recombinant equine follicle stimulating hormone (reFSH), but neither pregnancy nor cyclicity was established in that study. Starting on December 1, 20 deep-anestrous mares of light horse breeds (4-15 y old) with follicles ≤ 20 mm in diameter and progesterone < 1 ng/mL were maintained under natural photoperiod while 10 control mares were maintained under artificial photoperiod. Starting on February 6, treatment mares were randomly assigned to one of two groups: reFSH (n = 10) or reFSH/reLH (n = 10). Jugular blood samples were collected daily from all mares, and luteinizing hormone (LH), FSH, progesterone (P), estradiol-17β (E) and immunoreactive (ir)-inhibin were analyzed by radioimmunoassay (RIA). When the largest follicle reached ≥32 mm in diameter, reFSH treatment was discontinued in both groups while reLH treatment continued in the reFSH/reLH group until a cohort of follicles reached ≥35 mm in diameter. Human chorionic gonadotropin (hCG) was administered intravenously (iv) to induce ovulation, and mares were bred to a fertile stallion every other day until ovulation. Mares receiving either reFSH or reFSH/reLH developed follicles ≥35 mm within 5-6 d of treatment compared with 15.8 ± 3.4 d in the control group. Both reFSH and reFSH/reLH induced ovulation in 100% of the mares within 10 d after treatment resulting in an 80% conception rate and a 70% pregnancy rate for both groups. Conception and pregnancy were designated as either presence of a 14 d old embryo (n = 16) or a fetal heartbeat at 24 d (n = 14), respectively. Only three mares in the control group ovulated within the same treatment period. Later ovulations in the control group resulted in 100% conception and pregnancy rates. At 25 d post-conception, treated mares that were pregnant (n = 7 per group) were administered prostaglandin (PGF2) to terminate the pregnancy and later returned to estrus. Treatment with reFSH or reFSH/reLH given to deep-anestrous mares under natural photoperiod induced fertile ovulations that resulted in pregnancy and cyclicity when pregnancies were terminated.
在北半球，为了缩短母马一年中首次排卵的时间，最常见的繁殖做法是从12月1日开始使用人工光照。这种光照方案需要60 - 90天才能诱导出可受孕的排卵。用于实现相同过程的药物化合物的成功率各不相同。一种确实能诱导早期排卵的化合物是重组马促卵泡素（reFSH），但在该研究中既未建立妊娠也未建立周期性。从12月1日开始，选取20匹轻型马品种处于深度乏情期的母马（4 - 15岁），其卵泡直径≤20毫米且孕酮<1纳克/毫升，使其处于自然光照周期下，同时10匹对照母马处于人工光照周期下。从2月6日开始，将处理组母马随机分为两组：reFSH组（n = 10）或reFSH/reLH组（n = 10）。每天从所有母马采集颈静脉血样，通过放射免疫分析（RIA）测定促黄体生成素（LH）、促卵泡素（FSH）、孕酮（P）、雌二醇 - 17β（E）和免疫反应性（ir）抑制素。当最大卵泡直径达到≥32毫米时，两组均停止reFSH治疗，而reFSH/reLH组继续reLH治疗，直到一批卵泡直径达到≥35毫米。静脉注射人绒毛膜促性腺激素（hCG）诱导排卵，母马每隔一天与一匹可育种马交配直至排卵。接受reFSH或reFSH/reLH治疗的母马在治疗后5 - 6天内卵泡直径达到≥35毫米，而对照组为15.8±3.4天。reFSH和reFSH/reLH均在治疗后10天内使100%的母马排卵，两组的受孕率均为80%，妊娠率均为70%。受孕和妊娠分别定义为存在14天龄的胚胎（n = 16）或在24天时出现胎心（n = 14）。对照组中只有3匹母马在同一治疗期内排卵。对照组较晚的排卵导致受孕率和妊娠率均为100%。在受孕后25天，对怀孕的处理组母马（每组n = 7）给予前列腺素（PGF2）终止妊娠，随后恢复发情。在自然光照周期下，对深度乏情期母马给予reFSH或reFSH/reLH治疗可诱导出可受孕的排卵，当终止妊娠时会导致妊娠和周期性。
