Hawken P A R, Evans A C O, Beard A P
School of Agriculture, Food and Rural Development, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom.
Anim Reprod Sci. 2008 Jul;106(3-4):333-44. doi: 10.1016/j.anireprosci.2007.05.009. Epub 2007 May 18.
The ram effect is widely used in Mediterranean breeds of sheep but its use in temperate genotypes is restricted by breed seasonality. However, ewes from these highly seasonal genotypes are sensitive to stimulation by rams close to the onset of the natural breeding season. In this study we developed a pre-mating protocol of repeated, short-term exposure to rams (fence-line contact or vasectomised rams) beginning during late anoestrus and continuing into the breeding season. We hypothesised that this pre-mating protocol would synchronise the distribution of mating of North of England Mule ewes during the breeding season above that observed in ewes isolated from rams prior to mating. Ram-exposed ewes were given contact with rams (Experiment 1: fence-line; FR, n=94 and Experiment 2: vasectomised rams; VR; n=103) for 24h on Days 0 (10 September), 17 and 34 of the experiment. Control ewes (Experiment 1; FC, n=98 and Experiment 2; VC; n=106) remained isolated from rams prior to mating. In Experiment 2, a subset of VR (n=35) and VC ewes (n=35) were blood sampled twice weekly to monitor their pre-mating progesterone profiles. At mating, harnessed entire rams were introduced, 17 or 16 days after the last ram exposure (Experiments 1 and 2) and raddle marks were recorded daily. The median time from ram introduction to mating was reduced in ewes given both fence-line and vasectomised ram contact (P<0.001), leading to a more compact distribution of mating and lambing (At least P<0.01). In the blood sampled VR ewes, there was a progressive decline in the number of days from ram exposure to the onset of dioestrus (at least P<0.05). This observation indicates that the cycles in VR ewes became increasingly synchronised over the pre-mating period, a pattern not evident in VC ewes. In conclusion, repeated, short-term exposure of ewes to rams during the transition into the breeding season is an effective method of synchronising the distribution of mating during the breeding season.
公羊效应在地中海品种的绵羊中广泛应用，但在温带基因型绵羊中的应用受到品种季节性的限制。然而，这些高度季节性基因型的母羊在自然繁殖季节开始时对公羊的刺激很敏感。在本研究中，我们制定了一种配种前方案，即从发情后期开始，重复短期让母羊接触公羊（围栏接触或输精管结扎公羊），并持续到繁殖季节。我们假设，这种配种前方案将使英格兰北部穆勒母羊在繁殖季节的交配分布比配种前与公羊隔离的母羊更加同步。接触公羊的母羊在实验的第0天（9月10日）、第17天和第34天与公羊接触24小时（实验1：围栏接触；FR，n = 94；实验2：输精管结扎公羊；VR，n = 103）。对照母羊（实验1；FC，n = 98；实验2；VC，n = 106）在配种前与公羊隔离。在实验2中，对一部分VR（n = 35）和VC母羊（n = 35）每周采血两次，以监测它们配种前的孕酮水平。配种时，在最后一次接触公羊17或16天后引入佩戴挽具的成年公羊（实验1和2），并每天记录标记。与公羊进行围栏接触和输精管结扎公羊接触的母羊，从引入公羊到配种的中位时间缩短（P<0.001），导致交配和产羔分布更紧凑（至少P<0.01）。在采血的VR母羊中，从接触公羊到发情后期开始的天数逐渐减少（至少P<0.05）。这一观察结果表明，VR母羊的周期在配种前期变得越来越同步，而这种模式在VC母羊中不明显。总之，在进入繁殖季节的过渡阶段，让母羊反复短期接触公羊是使繁殖季节交配分布同步的有效方法。
