Rantala Mari H, Taponen Juhani
Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Saarentaus, Finland.
Department of Production Animal Medicine, Faculty of Veterinary Medicine, University of Helsinki, Saarentaus, Finland.
Theriogenology. 2015 Mar 1;83(4):497-503. doi: 10.1016/j.theriogenology.2014.10.012. Epub 2014 Oct 16.
The aim of this study was to investigate the effect of the stage of the estrus cycle (early vs. late diestrus) on the LH secretion after induced ovulation and on the incidence of short estrous cycles in dairy heifers. Cyclic heifers were presynchronized with dexcloprostenol and divided into Groups D7 (n = 6) and D14 (n = 6). On Day 7 (D7) or Day 14 (D14) after ovulation (Day 0), all animals were treated with dexcloprostenol followed by 0.1 mg of gonadorelin (GnRH) 24 hours later. Blood samples were taken daily for progesterone (P4) analysis and for LH analysis every 10 minutes for 3 hours on Days 1, 3, and 5 and every 30 minutes for 6 hours starting just before GnRH administration. In a control group, Group C (n = 7), estrus was synchronized with an intravaginal progesterone-releasing device (CIDR) inserted for 9 days. Blood for P4 analysis was taken daily for 16 days and for LH analysis every 30 minutes for 31 hours starting 30 hours after CIDR removal (unmanipulated LH peak) and every 10 minutes for 3 hours on Days 1, 3, and 5 after ovulation. In all groups, ovarian structures and ovulation were detected via daily transrectal ultrasound examination around first and second ovulation. In D7, all cycles (6/6) were shorter than normal (range 7-9 days). In D14, 2 of the 6 animals had a short cycle (both 7 days) whereas 4 had a cycle of normal length. All cycles were of normal length in C. Animals in D7 and D14 were divided according to their cycle length into short (SC) and normal (NC) cycle groups. The mean size of the ovulatory follicle during the 3 days before ovulation was significantly different between D7 and D14 and on 3 days and 1 day before ovulation between SC and NC. Secretion of LH during the 6 hours after GnRH administration did not differ between D7 and D14, or SC and NC. The mean basal LH secretion in D7 and D14 on Days 1, 3, and 5 was significantly different. No difference on those days was noted between SC and NC. In conclusion, when ovulation is induced with GnRH 24 hours after giving dexcloprostenol, short estrous cycles can occur during both early and late diestrus. The preovulatory LH surge did not differ between D7 and D14, or SC and NC. Also, basal LH secretion on Days 1, 3, and 5 was similar in SC and NC, and lower basal LH concentration coincided with higher P4 concentration.
本研究的目的是调查发情周期阶段（发情后期早期与晚期）对诱导排卵后促黄体生成素（LH）分泌以及奶牛小母牛短发情周期发生率的影响。对处于发情周期的小母牛先用双氯前列醇进行预处理，然后分为D7组（n = 6）和D14组（n = 6）。在排卵后第7天（D7）或第14天（D14）（第0天），所有动物均接受双氯前列醇治疗，24小时后再注射0.1 mg促性腺激素释放激素（GnRH）。每天采集血样进行孕酮（P4）分析，在第1、3和5天每10分钟采集一次血样进行LH分析，共3小时，从GnRH给药前开始，每30分钟采集一次血样，持续6小时。在对照组C组（n = 7）中，使用阴道内孕酮释放装置（CIDR）插入9天来同步发情。每天采集血样进行16天的P4分析，在CIDR取出后30小时（自然LH峰值）开始，每30分钟采集一次血样进行31小时的LH分析，在排卵后第1、3和5天每10分钟采集一次血样，共3小时。在所有组中，通过每天经直肠超声检查在第一次和第二次排卵前后检测卵巢结构和排卵情况。在D7组中，所有周期（6/6）均短于正常周期（范围为7 - 9天）。在D14组中，6只动物中有2只出现短周期（均为7天），而4只动物的周期长度正常。C组所有周期长度均正常。D7组和D14组的动物根据其周期长度分为短周期（SC）组和正常周期（NC）组。排卵前3天排卵卵泡的平均大小在D7组和D14组之间以及排卵前3天和1天在SC组和NC组之间存在显著差异。GnRH给药后6小时内LH的分泌在D7组和D14组之间或SC组和NC组之间没有差异。D7组和D14组在第1、3和5天的平均基础LH分泌存在显著差异。在这些天，SC组和NC组之间没有差异。总之，在用双氯前列醇24小时后用GnRH诱导排卵时，发情后期早期和晚期均可能出现短发情周期。排卵前LH高峰在D7组和D14组之间或SC组和NC组之间没有差异。此外，SC组和NC组在第1、3和5天的基础LH分泌相似，较低的基础LH浓度与较高的P4浓度一致。
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