Lammoglia M A, Short R E, Bellows S E, Bellows R A, MacNeil M D, Hafs H D
Fort Keogh Livestock and Range Research Laboratory, ARS, USDA, Miles City, MT 59301, USA.
J Anim Sci. 1998 Jun;76(6):1662-70. doi: 10.2527/1998.7661662x.
Peripubertal beef heifers (n = 57) and postpartum multiparous cows (n = 52) were used to determine the optimal dose of estradiol benzoate (EB) to induce and synchronize estrus after treatment with intravaginal progesterone inserts (IVP4, EAZI-BREED CIDR). All females received an IVP4 for 7 d (d 0 = insertion day) with a 25-mg injection of PGF2alpha (Lutalyse) on d 6. At 24 to 30 h after IVP4 removal, females were randomly assigned to be injected subcutaneously with EB at the following doses: heifers 0, .2, .38, or .75 mg and cows 0, .25, .5, or 1 mg. Furthermore, seven heifers and seven cows from each dose group were bled every 4 h for 76 h starting at EB injection. Serum was collected and assayed for LH and estradiol-17beta (E2). Observations for signs of estrus were made twice daily for 21 d after removal of IVP4, and females were artificially inseminated 8 to 20 h after detection of estrus. The percentage of females showing estrous behavior was increased by EB (P < .04); the greatest response was at .38 mg in heifers (86%) and 1 mg in cows (100%). Dose x time interaction affected (P < .01) E2 concentrations in heifers and cows; the animals that received the higher doses of EB had greater E2 concentrations in a shorter time than those that received the smaller doses. The percentage of cows and heifers with an acute preovulatory LH release (peak LH) was affected by dose, with a linear (P < .01) and a quadratic (P < .01) response. Highest concentrations of LH during peak LH were affected by dose with a linear (P < .01) response in heifers and linear (P < .01) and quadratic (P < .08) responses in cows. Heifers receiving .38 mg and cows receiving .5 and 1 mg of EB had the highest peak LH. Time to LH peak had a linear (P < .03) response in heifers and had linear (P < .04) and quadratic (P < .05) responses in cows. Pregnancy rate was affected (P < .02) in heifers by whether or not they were anestrous before IVP4 treatment (those with estrous cycles = 52% vs those that were anestrous = 22%) and in cows by dose of EB (P < .01; 8, 23, 21, and 67% for 0, .25, .5, and 1 mg, respectively). In conclusion, in females treated with IVP4 and PGF2alpha to induce and synchronize estrus, an injection of EB increased concentrations of E2 and LH and increased number of animals showing estrus. Also, EB increased pregnancy rates in cows. Optimal responses were at .38 mg EB for heifers and at 1 mg EB for cows.
选用青春期前后的小母牛（n = 57）和产后经产母牛（n = 52），以确定在使用阴道内孕酮植入物（IVP4，EAZI - BREED CIDR）处理后，诱导发情并使其同步的苯甲酸雌二醇（EB）最佳剂量。所有雌性动物均接受IVP4处理7天（第0天 = 植入日），并在第6天注射25毫克的前列腺素F2α（Lutalyse）。在取出IVP4后24至30小时，将雌性动物随机分为以下剂量皮下注射EB：小母牛分别为0、0.2、0.38或0.75毫克，母牛分别为0、0.25、0.5或1毫克。此外，从每个剂量组中选取7头小母牛和7头母牛，从注射EB开始，每4小时采血一次，共采血76小时。收集血清并检测促黄体生成素（LH）和雌二醇 - 17β（E2）。在取出IVP4后的21天内，每天观察两次发情迹象，在检测到发情后8至20小时对雌性动物进行人工授精。注射EB后出现发情行为的雌性动物百分比增加（P < 0.04）；小母牛中最大反应出现在0.38毫克剂量时（86%），母牛中出现在1毫克剂量时（100%）。剂量×时间交互作用影响（P < 0.01）小母牛和母牛的E2浓度；接受较高剂量EB的动物比接受较低剂量的动物在更短时间内具有更高的E2浓度。急性排卵前LH释放（LH峰值）的小母牛和母牛百分比受剂量影响，呈线性（P < 0.01）和二次曲线（P < 0.01）反应。LH峰值期间LH的最高浓度受剂量影响，小母牛呈线性（P < 0.01）反应，母牛呈线性（P < 0.01）和二次曲线（P < 0.08）反应。接受0.38毫克EB的小母牛和接受0.5毫克和1毫克EB的母牛具有最高的LH峰值。小母牛达到LH峰值的时间呈线性（P < 0.03）反应，母牛呈线性（P < 0.04）和二次曲线（P < 0.05）反应。小母牛的妊娠率受IVP4处理前是否处于乏情期影响（有发情周期的 = 52%，乏情的 = 22%）（P < 0.02），母牛的妊娠率受EB剂量影响（P < 0.01；0、0.25、0.5和1毫克剂量组分别为8%、23%、l21%和67%）。总之，在用IVP4和PGF2α处理以诱导发情并使其同步的雌性动物中，注射EB可增加E2和LH浓度，并增加出现发情的动物数量。此外，EB可提高母牛的妊娠率。小母牛的最佳反应剂量为0.38毫克EB，母牛为1毫克EB。
