Burke J M, Hampton J H, Staples C R, Thatcher W W
Department of Dairy and Poultry Sciences, University of Florida, Gainesville 32611, USA.
Theriogenology. 1998 Mar;49(4):751-60. doi: 10.1016/S0093-691X(98)00024-7.
The objective of this study was to determine whether plasma concentrations of progesterone (P4) from a controlled internal drug releasing (CIDR) device (approximately 2 ng/ml) were adequate to sustain a persistent first wave dominant follicle (FWDF) in low body condition (LBC, body condition score [BCS] 1 = lean, 5 = fat [2.3 +/- 0.72, n = 4]) compared with high body condition (HBC, BCS = 4.4 +/- 0.12, n = 4) nonlactating dairy cows. On Day 7 of the estrous cycle (Day 0 = estrus), cows were treated with PGF2 alpha (25 mg i.m. Lutalyse, P.M., and Day 8 A.M.) and a used CIDR device containing P4 (1.2 g) was inserted into the vagina until ovulation or Day 16. Plasma was collected for P4 and estradiol (E2) analyses from Day 5 to Day 18 (or ovulation), and ovarian follicles were monitored daily by ultrasonography. Mean concentrations of plasma P4 were greater in HBC than LBC cows between Days 5 and 7 (4.6 > 3.4 +/- 0.37 ng/ml; P < 0.04). All LBC cows maintained the first wave dominant follicle and ovulated after removal of the CIDR device (18.3 +/- 0.3 d, n = 3; Cow 4 lost the CIDR device on Day 11 and ovulated on Day 15), whereas in the HBC cows ovulation occurred during the period of CIDR exposure (11.3 +/- 0.3 d; n = 3; a fourth cow developed a luteinized first wave dominant follicle that did not ovulate during the experimental protocol on Day 19). Mean day of estrus was 17 +/- 0.4 for LBC (n = 3) and 10 +/- 0.4 for HBC (n = 3) cows. Sustained concentrations of plasma E2 (12.9 +/- 2.8 pg/ml; Days 8 to 17) in LBC cows reflected presence of an active persistent first wave dominant follicle. The differential effect of BCS on concentrations of plasma P4 (y = ng/ml) was reflected by the difference (P < 0.01) in regressions: yLBC = 19.9 - 3.49x + 0.166x2 vs yHBC = 37.3 - 7.04x + 0.340x2 (x = day of cycle, Days 7 to 12). Although P4 concentration was greater for HBC cows prior to Day 8, a greater clearance of plasma P4 released from the CIDR device in the absence of a CL altered follicular dynamics, leading to premature ovulation in the HBC cows. A greater basal concentration of P4 was sustained in LBC cows that permitted maintenance of a persistent first wave dominant follicle.
本研究的目的是确定来自可控内部药物释放（CIDR）装置的孕酮（P4）血浆浓度（约2 ng/ml）是否足以在低体况（LBC，体况评分[BCS]1=瘦，5=胖[2.3±0.72，n=4]）的非泌乳奶牛中维持持续的第一波优势卵泡（FWDF），并与高体况（HBC，BCS=4.4±0.12，n=4）的非泌乳奶牛进行比较。在发情周期的第7天（第0天=发情），给奶牛注射PGF2α（25 mg，肌肉注射，Lutalyse，下午，第8天上午），并将一个含有P4（1.2 g）的用过的CIDR装置插入阴道，直至排卵或第16天。从第5天到第18天（或排卵）采集血浆用于P4和雌二醇（E2）分析，并通过超声检查每天监测卵巢卵泡。在第5天至第7天期间，HBC奶牛的血浆P4平均浓度高于LBC奶牛（4.6>3.4±0.37 ng/ml；P<0.04）。所有LBC奶牛在取出CIDR装置后维持第一波优势卵泡并排卵（18.3±0.3天，n=3；奶牛4在第11天丢失CIDR装置并于第15天排卵），而在HBC奶牛中，排卵发生在CIDR暴露期间（11.3±0.3天；n=3；第四头奶牛形成了一个黄素化的第一波优势卵泡，在实验方案的第19天未排卵）。LBC（n=3）奶牛的平均发情日为17±0.4，HBC（n=3）奶牛为10±0.4。LBC奶牛中持续的血浆E2浓度（12.9±2.8 pg/ml；第8天至第17天）反映了活跃的持续第一波优势卵泡的存在。BCS对血浆P4浓度（y=ng/ml）的差异影响通过回归差异（P<0.01）反映：yLBC=19.9 - 3.49x + 0.166x2 与 yHBC=37.3 - 7.04x + 0.340x2（x=周期天数，第7天至第12天）。尽管在第8天之前HBC奶牛的P4浓度更高，但在没有黄体（CL）的情况下，从CIDR装置释放的血浆P4清除率更高，改变了卵泡动力学，导致HBC奶牛过早排卵。LBC奶牛维持了更高的基础P4浓度，从而允许维持持续的第一波优势卵泡。
