PDF(Pubmed)
Abstract：
The impact of GnRH treatment on the day of TAI in beef cows has received limited investigation, especially concerning its association with estrus expression. Consequently, two experiments were conducted to assess the potential of GnRH treatment on the day of TAI to enhance fertility according to the expression or not of estrus in beef cows. Experiment 1 aimed to determine ovulation rate and luteal function, while Experiment 2 aimed to determine the effect of the two GnRH treatment approaches on pregnancy rate. In Experiment 1, multiparous Brangus suckling cows (n = 17) were submitted to an 8-day TAI protocol. Estrus occurrence was evaluated based on chalk removal on D10 (TAI) and cows were assigned to receive GnRH (25µg lecirelin; im) according to the group: GnRH (n = 7), regardless of estrus expression; or selectGnRH (n = 10), only cows not detected in estrus. Ovulation rate occurring until 77h after IVD removal did not differ (p = 0.17) between GnRH (85.7%; 6/7) and selectGnRH (100%; 10/10). Also, corpus luteum size and serum progesterone concentration were not affected (p>0.05) by treatments. In Experiment 2, crossbred taurine suckled cows (n = 384) were submitted to the same protocol as described in Experiment 1 and were randomly allocated to GnRH or selectGnRH groups. There was no difference in P/AI between groups (selectGnRH = 55.6%; GnRH = 54.3%; p = 0.7) 30 days after TAI. As expected, there was a pronounced effect (p<0.0001) of estrus expression on P/AI (Estrus = 61.5%; No estrus = 33.0%), regardless of group. In summary, ovulation timing and rate and luteal function did not differ between groups. Also, GnRH administration only in cows that do not show estrus is recommended, considering hormone savings and similar conception rate.
摘要：
GnRH处理对肉牛TAI日的影响已经得到了有限的调查，特别是关于它与发情表达的关联。因此,进行了两个实验，以评估在TAI当天GnRH治疗根据肉牛发情的表达与否增强生育力的潜力。实验一旨在确定排卵率和黄体功能，实验2旨在确定两种GnRH治疗方法对妊娠率的影响。在实验1中，将多胎Brangus乳牛（n=17）提交给8天的TAI方案。根据D10（TAI）上的白垩去除评估发情发生，并根据GnRH（n=7）组分配母牛接受GnRH（25µglecirelin;im），无论发情期表达如何；或选择GnRH(n=10)，只有在发情期没有检测到的奶牛。直到IVD去除后77小时发生的排卵率在GnRH(85.7%;6/7)和选择GnRH(100%;10/10)之间没有差异(p=0.17)。此外，黄体大小和血清孕酮浓度不受治疗影响(p>0.05)。在实验2中，将杂交牛磺酸乳牛（n=384）接受与实验1中所述相同的方案，并随机分配到GnRH或选择GnRH组。TAI后30天，两组之间的P/AI无差异（选择GnRH=55.6％；GnRH=54.3％；p=0.7）。不出所料,发情表达对P/AI有明显影响（p<0.0001）（发情=61.5％；无发情=33.0％），无论群体。总之,两组间排卵时间、排卵率和黄体功能无差异。此外，建议仅在不显示发情的母牛中使用GnRH，考虑到激素储蓄和类似的受孕率。
