Stegner J E, Kojima F N, Ellersieck M R, Lucy M C, Smith M F, Patterson D J
Department of Animal Science, University of Missouri, Columbia 65211, USA.
J Anim Sci. 2004 Apr;82(4):1016-21. doi: 10.2527/2004.8241016x.
Two progestin-based protocols for estrus synchronization in postpartum beef cows were compared following treatment administration on the basis of estrous response, interval to and synchrony of estrus, and pregnancy. Cows were assigned to one of the two treatment protocols by age, body condition score (BCS), and days postpartum (DPP). The MGA Select-treated cows (MGA Select; n = 109) were fed melengestrol acetate (MGA; 0.5mg x cow-1 x d(-1)) for 14 d, fed carrier for 8 d, GnRH (100 microg of Cystorelin) was injected i.m. 12 d after MGA withdrawal, and PG (25 mg of Lutalyse) was administered i.m. 7 d after GnRH. Cows assigned to the 7-11 Synch protocol (7-11 Synch; n = 111) were fed carrier for 15 d, fed MGA for 7 d, injected with PG on d 22 (d 7 of MGA), injected with GnRH on d 26, and injected with PG on d 33. Mean BCS (4.8 +/- 0.1, MGA Select; 4.7 +/- 0.1, 7-11 Synch) and DPP (40 +/- 1, MGA Select; 40 +/- 1, 7-11 Synch) did not differ between treatments. Blood samples were collected 8 d and 1 d before feeding of MGA or carrier to determine the pretreatment estrous cyclicity (progesterone > or = 1 ng/mL; 10/109 [9%], MGA Select; 12/111 [11%], 7-11 Synch), and again at PG on d 33 to evaluate treatment response (81/109 [74%], MGA Select; 84/111 (76%), 7-11 Synch). Serum concentrations of progesterone at PG on d 33 differed (P < 0.01) between treatments (3.3 +/- 0.3 ng/mL [MGA Select] vs. 1.7 +/- 0.1 ng/mL [7-11 Synch]). HeatWatch was used for 6 d after PG on d 33 to detect estrus, and AI was performed 12 h after the onset of estrus. Estrous response did not differ between treatments (100/109 [92%], MGA Select; 101/111 [91%], 7-11 Synch). Mean interval to estrus (65 +/- 2.7 h, MGA Select; 52 +/- 1.8 h, 7-11 Synch) and synchrony of estrus differed (P < 0.01) between treatments. Synchronized conception and pregnancy rates (61/100 [61%], 61/109 [56%], MGA Select; 71/101 [70%], 71/111 [64%], 7-11 Synch), and final pregnancy rates (94/109 [86%], MGA Select; 99/110 [90%], 7-11 Synch) did not differ between treatments. In summary, estrous response and fertility did not differ among cows assigned to the MGA Select or 7-11 Synch protocols. Synchrony of estrus, defined as the variance in the interval to estrus from PG, however, was improved following treatment with the 7-11 Synch protocol.
在产后肉牛母牛中，根据发情反应、发情间隔和同步性以及妊娠情况，比较了两种基于孕激素的发情同步方案。根据年龄、体况评分（BCS）和产后天数（DPP），将母牛分配到两种处理方案之一。接受烯丙孕素选择处理的母牛（烯丙孕素选择组；n = 109），饲喂醋酸美仑孕酮（MGA；0.5mg/头·天），持续14天，之后饲喂载体8天，在停用MGA 12天后肌肉注射促性腺激素释放激素（GnRH，100μg的促排3号），在注射GnRH 7天后肌肉注射前列腺素（PG，25mg的氯前列醇）。分配到7-11同步方案组（7-11同步组；n = 111）的母牛，先饲喂载体15天，再饲喂MGA 7天，在第22天（MGA处理的第7天）注射PG，在第26天注射GnRH，在第33天注射PG。两种处理之间，平均BCS（4.8±0.1，烯丙孕素选择组；4.7±0.1，7-11同步组）和DPP（40±1，烯丙孕素选择组；40±1，7-11同步组）无差异。在饲喂MGA或载体前8天和1天采集血样，以确定预处理时的发情周期（孕酮≥1ng/mL；烯丙孕素选择组10/109 [9%]，7-11同步组12/111 [11%]），并在第33天注射PG时再次采集血样，以评估处理反应（烯丙孕素选择组81/109 [74%]，7-11同步组84/111 [76%]）。两种处理在第33天注射PG时的血清孕酮浓度存在差异（P < 0.01）（烯丙孕素选择组3.3±0.3ng/mL vs. 7-11同步组1.7±0.1ng/mL）。在第33天注射PG后，使用HeatWatch持续6天检测发情，并在发情开始后12小时进行人工授精。两种处理的发情反应无差异（烯丙孕素选择组100/109 [92%]，7-11同步组101/111 [91%]）。两种处理之间，平均发情间隔（烯丙孕素选择组65±2.7小时，7-11同步组52±1.8小时）和发情同步性存在差异（P < 0.01）。同步受孕率和妊娠率（烯丙孕素选择组61/100 [61%]，61/109 [56%]；7-11同步组71/101 [70%]，71/111 [64%]）以及最终妊娠率（烯丙孕素选择组94/109 [86%]，7-11同步组99/110 [90%]）在两种处理之间无差异。总之，分配到烯丙孕素选择或7-11同步方案的母牛，发情反应和繁殖力无差异。然而，将发情同步性定义为从注射PG到发情间隔的方差，7-11同步方案处理后得到了改善。
