The continuous presence of active male small ruminants prevents seasonal anestrus in females, but evidence of the same mechanism operating from the females to the males is scarce. This study assessed the effects of the continuous presence of ewes in estrus in spring on ram sexual activity, testicular size and echogenicity, and LH and testosterone concentrations. On 1 March, 20 rams were assigned to two groups (n = 10 each): isolated (ISO) from other sheep, or stimulated (STI) by 12 ewes, which were separated from the rams by an openwork metal barrier, allowing contact between sexes. Each week, four ewes were induced into estrus by intravaginal sponges. Live weight, scrotal circumference, testicular width (TW) and length (TL) were recorded at the beginning and at the end of the experiment, and testicular volume (TV) was calculated; at the same time, testicular ultrasonography and color Doppler scanning were performed. Blood samples (March to May) were collected once per week for testosterone determinations, and at the end of the experiment, blood samples were collected for 6 h at 20-min intervals for LH analysis. Rams were exposed to four estrous ewes in a serving-capacity test. Scrotal circumference, TW and TL were higher in the STI than in the ISO rams (P < 0.05) in May, and TV was higher (P < 0.05) in the STI (391 ± 17 cm3) than in the ISO rams (354 ± 24 cm3). In ISO rams, the number of white pixels was higher (P < 0.01) in May (348 ± 74) than in March (94 ± 21) and differed significantly (P < 0.01) from that of the STI rams in May (160 ± 33). In ISO rams, the number of grey pixels was higher (P < 0.05) in May (107 ± 3) than it was in March (99 ± 1). Stimulated and ISO rams did not differ significantly in mean LH plasma concentrations (0.8 ± 0.5 v. 0.9 ± 0.4 ng/ml), LH pulses (2.1 ± 0.5 v. 2.2 ± 0.2) and amplitude (2.0 ± 0.4 v. 3.2 ± 0.7 ng/ml, respectively). Stimulated rams had significantly higher testosterone concentrations than ISO rams from April to the end of the experiment. Stimulated rams performed more (P < 0.05) mountings with intromission (3.0 ± 0.4) than did ISO rams (1.5 ± 0.5). In conclusion, after 3 months in the continuous presence of ewes in estrus in spring, rams had higher TV and some testicular echogenic parameters were modified than isolated rams. Although exposed rams also had higher levels of testosterone after 2 months in the presence of estrous ewes, their LH pulsatility at the end of the study was not modified.

活跃的雄性小反刍动物的持续存在阻止了雌性的季节性发情，但是从雌性到雄性起作用的相同机制的证据却很少。这项研究评估了春季发情中母羊连续存在对公羊性活动，睾丸大小和回声，LH和睾丸激素浓度的影响。3月1日，将20只公羊分为两组（每组n = 10）：与其他绵羊隔离（ISO），或由12头母羊刺激（STI），它们通过镂空金属栅栏与公羊分开，从而允许性别。每周，阴道内海绵将四只母羊诱发发情。活体重，阴囊周长，睾丸宽度（TW）和长度（在实验开始和结束时记录TL），并计算睾丸体积（TV）。同时进行睾丸超声检查和彩色多普勒扫描。每周采集一次血样（3月至5月）以测定睾丸激素，在实验结束时，以20分钟的间隔采集血样6小时以进行LH分析。公羊在服役能力测试中暴露于四种发情母羊。阴囊周长，TW和TL分别在STI比ISO公羊（较高P在五月<0.05），和电视较高（P在STI（391±17 CM <0.05）3）比在ISO公羊（354 ±24厘米3）。在ISO公羊，白色像素的数目较高（P五月（348±74）<0.01）在三月（94±21）和显著差异（P从STI的<0.01）顶杆五月（160± 33）。在ISO公羊中，5月份（107±3）的灰度像素数量高于3月份（99±1）的灰度像素数量（P <0.05）。激和ISO公羊没有平均LH血浆浓度显著不同（0.8±0.5 v 0.9±0.4纳克/毫升），LH脉冲（2.1±0.5 v 2.2±0.2）和幅度（2.0±0.4 v 3.2±0.7 ng / ml）。从4月到实验结束，受刺激的公羊的睾丸激素浓度明显高于ISO公羊。受刺激的公羊表现更好（P<0.05）与ISO公羊（1.5±0.5）相比具有前倾（3.0±0.4）的安装座。结论是，在春季发情期连续出现母羊3个月后，公羊的TV值更高，一些睾丸的回声参数也比孤立的公羊高。尽管在有动情母羊的情况下暴露2个月后，公羊的睾丸激素水平也较高，但研究结束时它们的LH搏动性并未改变。