Stevenson J L, Dalton J C, Santos J E P, Sartori R, Ahmadzadeh A, Chebel R C
Caine Veterinary Teaching Center, University of Idaho, Moscow, Idaho 83844, USA.
J Dairy Sci. 2008 Aug;91(8):3045-56. doi: 10.3168/jds.2007-0625.
The objectives were to evaluate the effect of synchronization protocols on follicular development and estradiol 17-beta (E(2)) and progesterone (P(4)) concentrations in dairy heifers. In experiment 1, 36 heifers were assigned to 1 of 6 synchronization protocols in a 3 x 2 factorial design: presynchronization with GnRH on study d -6 or -9 [study d 0 = initiation of the Cosynch + CIDR (controlled internal drug releasing insert containing P(4)) protocol] or no presynchronization (control) and one injection of PGF(2 alpha) or not on study d 0. In experiment 2, 126 heifers were assigned to 1 of 4 synchronization protocols in a 2 x 2 factorial arrangement: presynchronization or not with GnRH on study d -6 and injection of PGF(2 alpha) or not on study d 0. In experiments 1 and 2, all heifers received a modified Cosynch protocol with CIDR for 7 d starting on study d 0. After the PGF(2 alpha) of the Cosynch and removal of the CIDR, heifers were detected in estrus and inseminated. Those not inseminated by study d 10 received an injection of GnRH and were timed-inseminated. Ovaries were scanned by ultrasound on d 0, 2, and 5, daily from d 7 to 14, and on d 16. Blood samples collected on d 0, 2, 7, 9, and 16 were analyzed for P(4), and the blood sample collected on d 9 was analyzed for E(2). Pregnancy was diagnosed at 28 and 40 +/- 3 d after artificial insemination. In experiment 1, there was a tendency for the presynchronization protocol to affect the proportion of heifers ovulating in response to the first GnRH injection of the Cosynch + CIDR protocol. In experiment 2, a greater proportion of presynchronized heifers ovulated in response to the first GnRH injection. Although heifers receiving PGF(2 alpha) had larger ovulatory follicles on d 7 and before ovulation and shorter intervals to estrus and ovulation, these heifers tended to have decreased concentrations of E(2) during proestrus. Presynchronization of dairy heifers with GnRH increased ovulation in response to the first GnRH injection, and treatment of heifers with PGF(2 alpha) at initiation of the Cosynch + CIDR protocol increased the size of the ovulatory follicle and reduced the intervals to estrus and ovulation.
本研究旨在评估同步化方案对奶牛小母牛卵泡发育以及雌二醇17-β（E₂）和孕酮（P₄）浓度的影响。在实验1中，36头小母牛按3×2析因设计被分配至6种同步化方案中的一种：在研究第-6天或-9天用促性腺激素释放激素（GnRH）进行预同步化处理[研究第0天 = 启动同步发情+含孕酮（P₄）的控制内部药物释放装置（CIDR）方案]，或不进行预同步化处理（对照），且在研究第0天注射或不注射前列腺素F₂α（PGF₂α）。在实验2中，126头小母牛按2×2析因安排被分配至4种同步化方案中的一种：在研究第-6天进行或不进行GnRH预同步化处理，且在研究第0天注射或不注射PGF₂α。在实验1和实验2中，所有小母牛均从研究第0天开始接受含CIDR的改良同步发情方案，持续7天。在同步发情的PGF₂α处理后且移除CIDR后，对小母牛进行发情检测并输精。那些在研究第10天未输精的小母牛注射GnRH并进行定时输精。在第0天、第2天和第5天，从第7天至第14天每天以及在第16天用超声扫描卵巢。对在第0天、第2天、第7天、第9天和第16天采集的血样分析P₄，对在第9天采集的血样分析E₂。在人工授精后28天和40±3天诊断妊娠。在实验1中，预同步化方案有影响小母牛对同步发情+CIDR方案首次GnRH注射产生排卵反应比例的趋势。在实验2中，更大比例的预同步化小母牛对首次GnRH注射产生排卵反应。尽管接受PGF₂α的小母牛在第7天及排卵前有更大的排卵卵泡，且发情和排卵间隔更短，但这些小母牛在发情前期E₂浓度往往降低。用GnRH对奶牛小母牛进行预同步化处理可增加对首次GnRH注射的排卵反应，且在同步发情+CIDR方案开始时用PGF₂α处理小母牛可增加排卵卵泡大小并缩短发情和排卵间隔。
