Departamento de Fisiología, Facultad de Veterinaria, Lasplaces 1550, Montevideo 11600, Uruguay.
Anim Reprod Sci. 2011 Mar;124(1-2):65-8. doi: 10.1016/j.anireprosci.2011.02.021. Epub 2011 Feb 18.
The role of the ram effect on the reproductive performance of ewes that have initiated estrous cycles following lambing in combination with synchronization of estrus using PGF(2α) was examined. A total of 1264 Corriedale × Merino ewes in the breeding season (March-April) were allocated to one of three treatments. The control group (PG2) of ewes (n=415) were in permanent direct contact with vasectomized rams throughout the experiment from 60 d prior to the administration of the first luteolytic dose of PGF(2α) which was followed by a second dose 13 d later (Day 0 of the experiment). Ewes assigned to the other two treatments remained isolated from rams until Day 0. In the second treatment, ewes (PG2RE; n=445) were administered PGF(2α) in the same manner and were joined with vasectomized rams at Day 0. Ewes allocated to the third treatment (PGRE; n=404) did not receive the second dose of PGF(2α) but were introduced to vasectomized rams on Day 0. Sexual receptivity, as indicated by tail-head marking, was recorded until d 11. More PG2RE ewes (407/445; 92%) were observed in estrus by Day 11 than occurred for PG2 ewes (353/415; 85%; P=0.003). The accumulated frequency of PG2RE ewes in estrus was greater than for PG2 ewes for each period from Day 3 (P<0.001) to Day 11 (P<0.01). The onset of estrus was earlier in PG2RE ewes (2.98±0.07 d) than for PG2 ewes (3.31±0.07 d; P<0.0001). In contrast, the total frequency of PGRE ewes observed in estrus by Day 11 (356/404; 88%) was similar to that observed for PG2 ewes. However, the trajectory of the accumulated frequency of the incidence of estrus was less for the PGRE ewes initially, particularly during the period of Days 3-6 of observation (P<0.0001). Consequently, onset of estrus was earlier in PG2 ewes (3.31±0.07 d) than for PGRE ewes (5.30±0.11 d; P<0.0001). It was concluded that the introduction of vasectomized rams simultaneously with the second administration of PGF(2α) advanced the onset of estrus and increased the number of ewes that responded. The introduction of rams 13 d after a single dose of PGF(2α) did not substitute for the second administration of PGF(2α).
研究了发情周期启动后产羔与 PGF（2α）同期发情对母羊繁殖性能的公羊效应的作用。在繁殖季节（3-4 月），将 1264 只柯里代尔×美利奴母羊分配到三种处理中的一种。对照组（PG2）的母羊（n=415）在第一次用 PGF（2α）进行溶黄体处理前 60d 开始与去势公羊一直处于直接接触状态，然后在 13d 后（实验第 0 天）给予第二次剂量。其余两只处理的母羊直到第 0 天才与公羊隔离。在第二种处理中，PG2RE 母羊（n=445）以相同方式给予 PGF（2α），并在第 0 天与去势公羊交配。PGRE 母羊（n=404）未接受第二次 PGF（2α）剂量，但在第 0 天与去势公羊交配。直到第 11 天，通过尾巴标记记录性行为接受情况。与 PG2 母羊（353/415；85%；P=0.003）相比，更多的 PG2RE 母羊（407/445；92%）在第 11 天发情。PG2RE 母羊的发情累计频率在第 3 天（P<0.001）至第 11 天（P<0.01）期间均大于 PG2 母羊。PG2RE 母羊的发情开始时间较早（2.98±0.07d），而 PG2 母羊（3.31±0.07d；P<0.0001）。相比之下，到第 11 天观察到发情的 PGRE 母羊（356/404；88%）的总频率与 PG2 母羊相似。然而，PGRE 母羊发情的累计频率的轨迹最初较低，尤其是在观察的第 3-6 天期间（P<0.0001）。因此，PG2 母羊的发情开始时间较早（3.31±0.07d），而 PGRE 母羊（5.30±0.11d；P<0.0001）。结果表明，同时给予去势公羊和第二次 PGF（2α）可提前发情，并增加对 PGF（2α）有反应的母羊数量。在单次 PGF（2α）剂量后 13d 引入公羊并不能替代第二次 PGF（2α）的给予。
