Cavalieri J, Coleman C, Rodrigues H, Macmillan K L, Fitzpatrick L A
Department of Veterinary Science, University of Melbourne, Werribee, Victoria.
Aust Vet J. 2002 Apr;80(4):217-23. doi: 10.1111/j.1751-0813.2002.tb10817.x.
To compare the timing of onset of oestrus and ovulation, characteristics of oestrus, and fertility in Bos indicus heifers synchronised with a progesterone releasing intravaginal insert (IVP4) and administration of oestradiol benzoate (ODB) either at the time of removal of the insert or 24 h later.
Cohort study.
Bos indicus and Bos indicus cross heifers were treated on two farms (Farm A, n = 273; Farm B, n = 47) with an IVP4 for 8 days with 1.0 mg of ODB administered at the time of device insertion and 250 mg of cloprostenol at the time of device removal. Heifers in the ODB-0 group were administered 0.75 mg of ODB at the time of device removal while heifers in the ODB-24 group were administered the same dose of ODB 24 h after device removal. Heifers were inseminated once daily after detection of oestrus. Heifers not detected in oestrus by 72 h after removal of inserts were inseminated at that time. Oestrus was detected in heifers on Farm A using heatmount detectors while on Farm B oestrus in heifers was monitored using radiotelemetry of mounting pressure. Ovarian follicular development was monitored daily in 30 heifers on Farm B from the time of administration of inserts until ovulation to a maximum of 96 h after removal of inserts, and again 11 days after removal of inserts (Day 19). A blood sample was collected from all heifers on Farm B on Day 19 and analysed for plasma concentration of progesterone. Pregnancy was diagnosed 6 to 8 weeks after insemination.
Administration of ODB at the time of removal of inserts shortened the time interval to oestrus and ovulation (P < 0.001), increased the number of mounts recorded during oestrus (P = 0.04) and reduced the odds of pregnancy (P = 0.03). The proportion of heifers ovulating on Farm B was 67% and was not affected by treatment group (P = 0.61). The mean diameter of the largest follicle measured in ovaries was greater at the time of removal of inserts (9.1 +/- 0.6 vs 10.7 +/- 0.4; P = 0.03) and at the expected time of the LH surge (8.1 +/- 0.4 vs 11.5 +/- 0.3 mm; P < 0.001) in heifers that ovulated compared to heifers that failed to ovulate, respectively. Emergence of a new follicular wave was not detected during the synchronisation treatment in heifers that failed to ovulate. Concentrations of progesterone in plasma on Day 19 were less in non-pregnant heifers (P = 0.05) compared to heifers subsequently diagnosed as pregnant to insemination and were affected by the diameter of the ovulatory follicle (P = 0.01).
Administration of ODB at the time of removal of inserts can shorten the time interval to oestrus and ovulation and can reduce fertility when insemination is carried out once daily. Further work is needed to determine if prolonged suppression of follicular development, anovulatory oestrus and premature ovulation occuring in some heifers is associated with administration of ODB.
比较使用含孕酮阴道缓释装置（IVP4）同步发情的印度瘤牛小母牛，在取出装置时或24小时后注射苯甲酸雌二醇（ODB），其发情和排卵开始时间、发情特征及繁殖力。
队列研究。
在两个农场（农场A，n = 273；农场B，n = 47）对印度瘤牛和印度瘤牛杂交小母牛用IVP4处理8天，在装置插入时注射1.0 mg ODB，在装置取出时注射250 mg氯前列醇。ODB - 0组小母牛在装置取出时注射0.75 mg ODB，而ODB - 24组小母牛在装置取出后24小时注射相同剂量的ODB。发情检测到后，小母牛每天输精一次。取出装置后72小时内未检测到发情的小母牛在此时输精。在农场A使用发情监测器检测小母牛发情，而在农场B使用安装压力无线电遥测监测小母牛发情。在农场B，从装置给药时起至排卵，每天监测30头小母牛的卵巢卵泡发育，最长至取出装置后96小时，并在取出装置后11天（第19天）再次监测。在第19天从农场B的所有小母牛采集血样，分析血浆孕酮浓度。输精后6至8周诊断妊娠。
在取出装置时注射ODB缩短了发情和排卵的时间间隔（P < 0.001），增加了发情期间记录的爬跨次数（P = 0.04）并降低了妊娠几率（P = 0.03）。农场B排卵的小母牛比例为67%，且不受治疗组影响（P = 0.61）。与未排卵的小母牛相比，排卵小母牛在取出装置时（9.1±0.6对10.7±0.4；P = 0.03）和预期促黄体生成素激增时（8.1±0.4对11.5±0.3 mm；P < 0.001）卵巢中测量的最大卵泡平均直径更大。在未排卵的小母牛同步治疗期间未检测到新的卵泡波出现。与随后诊断为输精妊娠的小母牛相比，第19天未妊娠小母牛的血浆孕酮浓度较低（P = 0.05），且受排卵卵泡直径影响（P = 0.01）。
在取出装置时注射ODB可缩短发情和排卵的时间间隔，且每天输精一次时会降低繁殖力。需要进一步研究确定一些小母牛中出现的卵泡发育长期抑制、无排卵发情和过早排卵是否与注射ODB有关。
