Ungerfeld R, Ramos M A, González-Pensado S P
Departamento de Fisiología, Facultad de Veterinaria, Lasplaces 1550, Montevideo 11600, Uruguay.
Anim Reprod Sci. 2008 Jan 30;103(3-4):271-7. doi: 10.1016/j.anireprosci.2006.12.013. Epub 2006 Dec 16.
The introduction of rams to previously isolated anestrous ewes ensures induction of ovulation and estrus in part of the flock, and allows for the potential to conceive. However, there is little known about the desirable characteristics of the rams used to induce these behavioral and physiological responses. Adult rams may be more effective than young rams in induction of these responses. The primary aim of the present study was to compare the response in ewes stimulated by adult or yearling rams. During the non-breeding season, two groups of 121 ewes were stimulated with adult (AR) or yearling (YR) rams. When adult rams were used, significantly more ewes had ovulations (78.5 compared with 61.1%) and came into estrus (47.9 compared with 35.5%). There were more corpora lutea per ewe exposed to rams (0.95+/-0.59 compared with 0.65+/-0.51) and per ewe that had ovulations (1.18+/-0.41 compared with 1.06+/-0.25) and a greater conception rate (58.6 compared with 20.9%) as a result. Subsequently, to determine what signals led to the greater response to adult rams, the courtship behavior of adult and yearling rams toward anestrous ewes was compared in 46 pen tests. There were no significant differences in the frequency of any of the recorded courtship behaviors (anogenital sniffing: 21.9+/-3.4 versus 25.7+/-3.2; lateral approaches: 7.1+/-1.5 compared with 9.9+/-2.9; flehmen: 2.1+/-0.4 compared with 2.2+/-0.4; mount attempts: 0.1+/-0.1 compared with 0.1+/-0.1, for AR and YR, respectively), latency to the onset of courtship behavior (13.1+/-7.0 compared with 17.3+/-6.2s) or the time engaged in courtship behavior (173.1+/-24.6 compared with 199.0+/-26.5s). The difference in the signals produced by adult and yearling rams skin glands was assessed by stimulating ewes with masks containing wool from adult (n=45) or yearling (n=48) rams. More ewes had ovulations (24/45 compared with 11/48) and came into estrus (21/45 compared with 10/48) when wool from adult rams was used. As in Experiment 1, pregnancy and conception rates were greater when adult rams were used, another trial was designed to determine if there were differences in mating and mounting frequency between adult and yearling rams. Seven adult and six yearling rams were subjected to three pen tests each with three estrual ewes. Adult rams mounted more (21.7+/-4.5 compared with 9.8+/-0.7) and tended to ejaculate more frequently (2.9+/-0.5 compared with 1.8+/-0.4) than yearling rams. It is concluded that adult rams induce a greater reproductive response in anestrous ewes than yearling rams, inducing a greater ovulation percentage and estrous response in ewes, resulting in greater ovulation numbers, pregnancy and conception rates. This greater stimulation is, in part, explained by differences in the signals provided in the wool (presumably odors) produced by adult rams. The lesser percentage of pregnancies obtained when yearling rams are used may be explained by differences in mounting behaviors and ejaculation frequency.
将公羊引入先前处于隔离状态的乏情母羊中，可确保部分母羊群排卵并发情，从而具备受孕的可能性。然而，对于用于引发这些行为和生理反应的公羊的理想特征，人们了解甚少。成年公羊在引发这些反应方面可能比年轻公羊更有效。本研究的主要目的是比较成年公羊或周岁公羊刺激下母羊的反应。在非繁殖季节，两组各121只母羊分别由成年公羊（AR组）或周岁公羊（YR组）进行刺激。使用成年公羊时，有更多母羊排卵（分别为78.5%和61.1%）和发情（分别为47.9%和35.5%）。每只接触公羊的母羊黄体数量更多（分别为0.95±0.59和0.65±0.51），每只排卵母羊的黄体数量也更多（分别为1.18±0.41和1.06±0.25），受孕率也更高（分别为58.6%和20.9%）。随后，为了确定哪些信号导致对成年公羊有更大反应，在46次围栏试验中比较了成年公羊和周岁公羊对乏情母羊的求偶行为。记录的任何求偶行为的频率（肛门生殖器嗅闻：成年公羊21.9±3.4次，周岁公羊25.7±3.2次；侧向接近：成年公羊7.1±1.5次，周岁公羊9.9±2.9次；卷唇反应：成年公羊2.1±0.4次，周岁公羊2.2±0.4次；爬跨尝试：成年公羊0.1±0.1次，周岁公羊0.1±0.1次）、求偶行为开始的潜伏期（成年公羊13.1±7.0秒，周岁公羊17.3±6.2秒）或求偶行为持续时间（成年公羊173.1±24.6秒，周岁公羊199.0±26.5秒）均无显著差异。通过用含有成年公羊（n = 45）或周岁公羊（n = 48）羊毛的面罩刺激母羊，评估成年公羊和周岁公羊皮肤腺体产生的信号差异。使用成年公羊羊毛时，有更多母羊排卵（分别为24/45和11/48）和发情（分别为21/45和10/48）。与实验1一样，使用成年公羊时妊娠率和受孕率更高，因此设计了另一项试验来确定成年公羊和周岁公羊在交配和爬跨频率上是否存在差异。七只成年公羊和六只周岁公羊分别与三只发情母羊进行三次围栏试验。成年公羊的爬跨次数更多（分别为21.7±4.5次和9.8±0.7次），射精频率也更高（分别为2.9±0.5次和1.
