IUCA, Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, Miguel Servet, 177, 50013, Zaragoza, Spain.
Physiologie de la Reproduction et des Comportements, UMR INRA, CNRS, Université de Tours, IFCE, Agreenium, 37380, Nouzilly, France.
Theriogenology. 2019 Sep 15;136:43-46. doi: 10.1016/j.theriogenology.2019.06.032. Epub 2019 Jun 19.
The effect of the continuous presence of sexually active Rasa Aragonesa rams on the plasma luteinizing-hormone (LH) concentrations of ewes was studied from November to May. Light-treated rams were rendered sexually active (SA rams) by exposure to 2 months of artificially long days (16 h light/8 h dark) in one of two groups from either 1 November (SAR1, n = 3) or 1 December (SAR2, n = 3). Rams (n = 6) in a Control group were kept under the natural photoperiod. Thirty ewes were ovariectomized in September and implanted with a subcutaneous implant (l = 15 mm) that contained estradiol-17β. One group of ewes (SAR; n = 10) was housed with control rams from 1 October to 15 February before being housed with SAR1 rams from 16 February to 31 March, and with SAR2 rams from 1 April to 31 May. A second group of ewes (C; n = 10) remained with control rams throughout the experiment, and a third group was kept isolated from rams throughout the experiment (ISO; n = 10). Blood samples were collected weekly from November to May, and plasma LH concentrations were measured. In the breeding season (November-February), plasma LH concentrations of ewes did not differ significantly between groups (SAR: 2.00 ± 0.34; C: 1.88 ± 0.16; ISO: 1.67 ± 0.51 ng/ml). From March to May (seasonal anestrus), however, LH plasma concentrations decreased in the C and ISO groups (1.30 ± 0.20 and 0.48 ± 0.04 ng/ml, respectively), but remained at the same level as in the breeding season in the SAR group (2.30 ± 0.17 ng/ml; P < 0.001). Significant differences (P < 0.01) between groups were observed from March onwards: LH concentrations were highest in SAR ewes (P < 0.001) and lowest in the ISO ewes. In conclusion, the continuous presence of sexually active rams prevented the seasonal decrease in plasma LH concentrations, probably by preventing the seasonal negative feedback of estradiol on LH secretion.
从 11 月到 5 月，研究了性活跃的拉沙罗萨公绵羊的持续存在对发情母羊血浆促黄体生成素（LH）浓度的影响。两组中的一组于 11 月 1 日（SAR1，n=3）或 12 月 1 日（SAR2，n=3）开始接受为期 2 个月的人工长日照（16 小时光照/8 小时黑暗），使光照处理的公羊（SAR 公羊）变得性活跃。对照组中的公羊（n=6）保持自然光照周期。30 只母羊于 9 月行卵巢切除术，并植入皮下植入物（l=15mm），其中含有雌二醇-17β。一组母羊（SAR；n=10）于 10 月 1 日至 2 月 15 日与对照公羊一起饲养，然后于 2 月 16 日至 3 月 31 日与 SAR1 公羊一起饲养，于 4 月 1 日至 5 月 31 日与 SAR2 公羊一起饲养。第二组母羊（C；n=10）在整个实验过程中与对照公羊一起饲养，第三组母羊（ISO；n=10）在整个实验过程中与公羊隔离。从 11 月到 5 月每周采集一次血样，测量血浆 LH 浓度。在繁殖季节（11 月至 2 月），各组母羊的血浆 LH 浓度无显著差异（SAR：2.00±0.34；C：1.88±0.16；ISO：1.67±0.51ng/ml）。然而，从 3 月到 5 月（季节性乏情），C 组和 ISO 组的 LH 血浆浓度下降（分别为 1.30±0.20 和 0.48±0.04ng/ml），但 SAR 组仍保持繁殖季节的水平（2.30±0.17ng/ml；P<0.001）。从 3 月开始，组间观察到显著差异（P<0.01）：SAR 母羊的 LH 浓度最高（P<0.001），ISO 母羊的 LH 浓度最低。综上所述，性活跃公羊的持续存在阻止了血浆 LH 浓度的季节性下降，这可能是通过阻止雌二醇对 LH 分泌的季节性负反馈来实现的。
