Leitman N R, Busch D C, Bader J F, Mallory D A, Wilson D J, Lucy M C, Ellersieck M R, Smith M F, Patterson D J
Division of Animal Science, S132 ASRC, University of Missouri, Columbia 65211, USA.
J Anim Sci. 2008 Aug;86(8):1808-18. doi: 10.2527/jas.2008-0970. Epub 2008 Apr 11.
The objective of the experiment was to compare follicular dynamics, ovulatory response to GnRH, and synchrony of estrus and ovulation among estrous-cycling and prepubertal beef heifers synchronized with a controlled internal drug-release (CIDR)- based or GnRH-PGF(2alpha) (PG) protocol. Estrous-cycling beef heifers were randomly assigned to 1 of 4 treatments (C1, C2, C3, C4), and prepubertal beef heifers were randomly assigned to 1 of 2 treatments (P1, P2) by age and BW. Blood samples were taken 10 and 1 d before treatment to confirm estrous cyclicity status (progesterone > or =0.5 ng/mL estrous cycling). The CIDR Select (C1, n = 12; P1, n = 14)-treated heifers received a CIDR insert (1.38 g of progesterone) from d 0 to 14, GnRH (100 microg, i.m.) on d 23, and PG (25 mg, i.m.) on d 30. Select Synch + CIDR (C2, n = 12; P2, n = 11)-treated heifers received a CIDR insert and GnRH on d 23 and PG at CIDR removal on d 30. The CIDR-PG (C3, n = 12)-treated heifers received a CIDR insert on d 23 and PG at CIDR removal on d 30. Select Synch (C4, n = 12)-treated heifers received GnRH on d 23 and PG on d 30. HeatWatch transmitters were fitted at CIDR removal (C1, C2, C3, P1, and P2) or at GnRH administration (C4) for estrus detection. Ultrasound was used to determine the response to GnRH and the timing of ovulation after estrus. Among the estrous-cycling heifers, ovulatory response to GnRH and estrous response did not differ (P > 0.05). Among the prepubertal heifers, more (P = 0.02) P1 heifers responded to GnRH than P2 heifers, but estrous response did not differ (P > 0.05). Among the estrous-cycling heifers, variance for interval to estrus after PG was reduced (P < 0.05) for C1 compared with each of the other treatments, and C3 [corrected] was reduced (P < 0.05) compared with C2 [corrected] Variance for interval to ovulation after PG was reduced (P < 0.05) for C1 compared with each of the other treatments. Among the prepubertal heifers, there was no difference (P > 0.05) in variance for interval to estrus or ovulation. Results from C1 and P1 (T1) and C2 and P2 (T2) were combined to compare T1 and T2 among mixed groups of estrous-cycling and prepubertal heifers. Response to GnRH was greater (P < 0.01; 81% T1 and 39% T2), and variances for interval to estrus and ovulation for T1 were reduced (P < 0.01) compared with T2. In summary, CIDR Select improved (P < 0.01) the synchrony of estrus and ovulation compared with Select Synch + CIDR.
本实验的目的是比较在使用基于控制内部药物释放（CIDR）或促性腺激素释放激素-前列腺素F2α（PG）方案进行同期发情处理的发情周期母牛和青春期前小母牛中，卵泡动态、对促性腺激素释放激素（GnRH）的排卵反应以及发情和排卵的同步性。将发情周期母牛按年龄和体重随机分为4种处理之一（C1、C2、C3、C4），青春期前小母牛按年龄和体重随机分为2种处理之一（P1、P2）。在处理前10天和1天采集血样，以确认发情周期状态（孕酮≥0.5 ng/mL为发情周期）。接受CIDR Select（C1，n = 12；P1，n = 14）处理的小母牛在第0至14天植入CIDR栓（含1.38 g孕酮），在第23天肌肉注射GnRH（100 μg），在第30天肌肉注射PG（25 mg）。接受Select Synch + CIDR（C2，n = 12；P2，n = 11）处理的小母牛在第23天植入CIDR栓并注射GnRH，在第30天取出CIDR时注射PG。接受CIDR-PG（C3，n = 12）处理的小母牛在第23天植入CIDR栓，在第30天取出CIDR时注射PG。接受Select Synch（C4，n = 12）处理的小母牛在第23天注射GnRH，在第30天注射PG。在取出CIDR时（C1、C2、C3、P1和P2）或注射GnRH时（C4）安装HeatWatch发射器以检测发情。使用超声确定对GnRH的反应以及发情后排卵的时间。在发情周期母牛中，对GnRH的排卵反应和发情反应无差异（P>0.05）。在青春期前小母牛中，P1组对GnRH有反应的小母牛比P2组多（P = 0.02），但发情反应无差异（P>0.05）。在发情周期母牛中，与其他各处理相比，C1组PG处理后至发情间隔的方差减小（P<0.05），与C2组相比，C3组PG处理后至排卵间隔的方差减小（P<0.05）。在青春期前小母牛中，至发情或排卵间隔的方差无差异（P>0.05）。将C1和P1（T1）以及C2和P2（T2）的结果合并，以比较发情周期母牛和青春期前小母牛混合组中的T1和T2。与T2相比，T1对GnRH的反应更强（P<0.01；T1为81%，T2为39%），且T1至发情和排卵间隔的方差减小（P<0.01）。总之，与Select Synch + CIDR相比，CIDR Select改善了（P<0.01）发情和排卵的同步性。
