The aims of this study were to: 1) determine if the insertion of a second MAP sponge in ewes 12 days after the first FTAI affects the pregnancy rate; 2) compare the responses to resynchronization protocol in multiparous and nulliparous ewes; and 3) compare the responses to resynchronization protocol in multiparous and postpartum lactating ewes. Three trials were performed with 186 Corriedale ewes: 111 multiparous [(control – CON (n = 60) and synchronization – SYNC groups (n = 51)], forty-two 1.5 yr-old nulliparous (group NUL), and 33 lactating ewes with at least 28 postpartum (group PtP). All ewes were treated with a MAP sponge for 6 days. Twenty-four hours before the sponge withdrawal, all animals received 0.24 mg of cloprostenol sodium and 300 IU of eCG, and 0.05 mg of gonadorelin 36 h after sponge withdrawal and artificially inseminated (AI) 27-30 h after the GnRH administration (Day 0). A second intravaginal sponge was inserted to all groups (except for SYNC group), on Day 12. On Day 17, early pregnancy diagnosis was performed with doppler ultrasound in all ewes. Sponge withdrawal occurred on Day 18, and a new GnRH dose (0.05 mg) was administrated 36 h after it. Once again, AI 27-30 h after the GnRH administration. A final pregnancy diagnosis on Day 42 was performed in all ewes for confirmation of first diagnosis and the data were confirmed by parturition. Ewes in all groups presented estrus signs (SYNCH – 94.1%; CON – 71.7%; NUL – 83.3%; PtP – 39.4% at first AI and CON – 65.2%; NUL – 76.5%; PtP – 62.5% at the second). Pregnancy rate and pregnancy loss were not different between synchronized and resynchronized multiparous ewes (SYNCH – 56.9% vs. CON – 58.3% pregnant at D42 and SYNCH – 5.9% vs. CON – 7.1% fetal loss at D42). No differences were found between resynchronized multiparous and nulliparous ewes at the first FTAI, only fecundity was higher in multiparous ewes [CON – 0.88 vs. NUL – 0.62 (P = 0.04)]. Resynchronized multiparous ewes had higher reproductive performance than postpartum ewes that only presented pregnancy after the second FTAI [CON – 73.3% vs. PtP – 15.1% total pregnancy (P = 0.003)]. Overall, synchronization-resynchronization FTAI treatments may be included in reproductive programs in nulliparous ewes, but the treatments cannot superimpose to the limiting conditions imposed by postpartum lactating status. The resynchronization treatments allow to include practical managements with no deleterious effects in the results of the first FTAI.

这项研究的目的是：1）确定第一次FTAI后12天在母羊中插入第二只MAP海绵是否影响怀孕率；2）比较多头母羊和零头母羊对再同步协议的响应；3）比较产后和产后泌乳母羊对再同步方案的反应。对186头Corriedale母羊进行了三项试验：111头多胎[（对照组– CON（n = 60）和同步– SYNC组（n = 51）]，42头1.5岁的未产母羊（NUL组）和33头泌乳母羊至少有28个产后（PtP组），所有母羊均用MAP海绵处理6天，在撤回海绵的24小时前，所有动物均接受0.24 mg的氯前列腺素钠和300 IU的eCG，0。撤除海绵后36 h服用05 mg的促性腺激素，并在GnRH给药后27-30 h（第0天）进行人工授精（AI）。在第12天，向所有组（SYNC组除外）插入第二只阴道海绵。在第17天，用多普勒超声对所有母羊进行早期妊娠诊断。在第18天发生海绵撤离，并且在其后36小时施用新的GnRH剂量（0.05mg）。再次在GnRH给药后27-30小时AI。在第42天，对所有母羊进行了最终妊娠诊断，以确认首次诊断，并通过分娩确认了数据。所有组中的母羊都有发情征兆（SYNCH – 94.1％； CON – 71.7％； NUL – 83.3％； PtP –第一次AI占39.4％； CON – 65.2％； NUL – 76.5％； PtP –其次是62.5％）。同步母羊和再同步母羊的妊娠率和妊娠损失没有差异（D42孕妇的SYNCH – 56.9％vs CON –孕妇58.3％，SYNCH – 5.9％vs. CON – 7.1％孕妇在D42）。在第一次FTAI上，重新同步的母羊和零胎母羊之间没有发现差异，只有母羊的繁殖力更高[CON – 0.88 vs. NUL – 0.62（P = 0.04）]。重同步多胎母羊的生殖性能要高于仅在第二次FTAI后才怀孕的产后母羊[CON – 73.3％vs. PtP – 15.1％的总妊娠（P = 0.003）]。总的来说，同步-不同步FTAI处理可包括在未产母羊的生殖程序中，但是这些处理不能叠加到产后泌乳状态所施加的限制条件上。