In small ruminants, testosterone and prolactin plasma concentrations show circannual fluctuations as an adaptation mechanism to their seasonal breeding behavior. Sperm resistance to the freezing–thawing process shows seasonal fluctuation throughout the year, with lower sperm freezability at the beginning of the breeding season when prolactin and testosterone levels reach their maximum concentration. Nevertheless, whether these hormones directly affect post-thaw sperm quality parameters is still unclear. The objective was to study the effect of testosterone or prolactin added in vitro on sperm freezability in domestic ram (Ovis aries) and buck (Capra hircus). Sperm samples were incubated for 1 h with a range of testosterone (0, 2, 4, or 6 ng/mL; Exp. 1) or prolactin (0, 20, 100, 200, or 400 ng/mL; Exp. 2) concentrations. Samples were cryopreserved by slow freezing in straws at 0 h and after 1 h incubation. Sperm viability, acrosome integrity, motility, and kinetic parameters were assessed at 0 and 1 h in fresh and frozen-thawed samples. Results showed no hormone effect in fresh sperm, whereas these hormones affected post-thaw sperm parameters. In Exp. 1, in vitro incubation with testosterone decreased the post-thaw acrosome integrity of ram sperm (from 68.1 ± 6.3% to 49.6 ± 3.9%; P < 0.05). In Exp. 2, in vitro incubation with prolactin decreased the post-thaw acrosome integrity of ram (from 78.2 ± 3.4% to 66.3 ± 3.5%; P < 0.05) and buck sperm (from 81.7 ± 2.5% to 67.6 ± 3.5%; P < 0.05). Moreover, prolactin increased the post-thaw amplitude of lateral head displacement in ram sperm (from 3.3 ± 0.1 μm to 3.8 ± 0.2 μm; P < 0.05). In conclusion, either testosterone or prolactin added in vitro decreased the post-thaw acrosome integrity of ram and buck sperm. This suggests a destabilization process that could be decreasing sperm freezability when physiological levels of these hormones are high in vivo.

在小型反刍动物中，睾丸激素和催乳素的血浆浓度显示出年度波动，这是其季节性繁殖行为的适应机制。精子对冷冻-解冻过程的抵抗力在全年呈季节性波动，当催乳素和睾丸激素水平达到最大浓度时，在繁殖季节开始时精子的可冻结性降低。然而，这些激素是否直接影响解冻后的精子质量参数仍不清楚。目的是研究体外添加睾丸激素或催乳素对家养公羊（Ovis aries）和巴克（Capra hircus）精子可冻结性的影响。）。将精子样品与一系列睾丸激素（0、2、4或6 ng / mL;实验1）或催乳素（0、20、100、200或400 ng / mL;实验2）孵育1小时浓度。通过在0 h和孵育1 h后在吸管中缓慢冷冻将样品冷冻保存。在新鲜和冰冻融化的样品中，在0和1 h评估精子活力，顶体完整性，运动性和动力学参数。结果显示新鲜精子没有激素作用，而这些激素会影响解冻后的精子参数。在实验中 如图1所示，在体外与睾丸激素一起孵育会降低ram精子的解冻后顶体完整性（从68.1±6.3％降至49.6±3.9％；P <0.05）。在实验中 2，与催乳激素的体外孵育降低了羊的解冻后顶体完整性（从78.2±3.4％降至66.3±3.5％；P<0.05）和巴克精子（从81.7±2.5％到67.6±3.5％; P <0.05）。此外，催乳素增加了公羊精子的解冻后侧脑顶移位幅度（从3.3±0.1μm增至3.8±0.2μm；P <0.05）。总之，在体外添加睾丸激素或催乳激素都会降低公羊和巴克精子的解冻后顶体完整性。这表明当体内这些激素的生理水平较高时，其失稳过程可能会降低精子的冻结能力。