Diaz T, Schmitt E J, de la Sota R L, Thatcher M J, Thatcher W W
Department of Dairy and Poultry Sciences, University of Florida, Gainesville 32611-0920, USA.
J Anim Sci. 1998 Jul;76(7):1929-36. doi: 10.2527/1998.7671929x.
This experiment was designed to characterize hCG (3,000 IU)-induced alterations in ovarian follicular and corpus luteum (CL) dynamics during the estrous cycle (EC) in heifers. Following synchronization of estrus (norgestomet implant for 7 d with injection of PGF2alpha 1 d before implant removal), 13 heifers were treated with either hCG (n = 6) or saline (control group; n = 7) on d 5 of the EC (d 0 = day of estrus). Blood sampling from the jugular vein and ultrasonography of both ovaries were conducted daily until confirmation of ovulation following a detected estrus. Treatment with hCG at d 5 induced formation of an accessory CL in all hCG-treated heifers. Subsequent plasma progesterone (P4) concentrations were higher (P < .01) between d 9 and 17 for the hCG group than for the control group. More (P < .05) hCG-treated heifers had EC with three waves of follicles than control heifers. The second-wave dominant follicle (DF) emerged earlier in hCG than in control heifers (7.3 vs 10.4 d; P < .01). A group x wave interaction (P < .01) was detected for duration of the second and third wave follicles; hCG treatment decreased duration of the second wave (6.3 vs 9.3 d) and increased duration of the third wave (9.2 vs 5.3 d). The hCG-treated heifers had preovulatory follicles that lasted longer (P < .01) on the ovary than those in control heifers. However, plasma estradiol concentrations did not differ (P > .10) between hCG-treated and control heifers during the preovulatory period. A wave x duration interaction (P < .01) was detected for P4 concentrations, between d 13 and 22, for heifers with two vs three spontaneous-wave EC. Higher P4 concentrations during the luteal phase may contribute to a greater rate of follicular turnover or frequency of three-wave cycles, and lower P4 concentrations were associated with two-wave cycles.
本实验旨在描述在小母牛发情周期（EC）中，人绒毛膜促性腺激素（hCG，3000国际单位）诱导的卵巢卵泡和黄体（CL）动态变化。在发情同步后（用诺孕美特植入剂处理7天，并在移除植入剂前1天注射前列腺素F2α），在发情周期的第5天（第0天 = 发情日），13头小母牛分别接受hCG处理（n = 6）或生理盐水处理（对照组；n = 7）。每天从颈静脉采血，并对两侧卵巢进行超声检查，直至检测到发情后确认排卵。在第5天用hCG处理导致所有接受hCG处理的小母牛均形成了副黄体。在第9至17天期间，hCG组的血浆孕酮（P4）浓度高于对照组（P < 0.01）。与对照小母牛相比，接受hCG处理的小母牛出现三波卵泡的发情周期更多（P < 0.05）。hCG处理的小母牛中，第二波优势卵泡（DF）出现的时间比对照小母牛更早（7.3天对10.4天；P < 0.01）。检测到第二波和第三波卵泡持续时间存在组×波的交互作用（P < 0.01）；hCG处理缩短了第二波的持续时间（6.3天对9.3天），并延长了第三波的持续时间（9.2天对5.3天）。接受hCG处理的小母牛的排卵前卵泡在卵巢上持续的时间比对照小母牛更长（P < 0.01）。然而，在排卵前期，接受hCG处理的小母牛与对照小母牛之间的血浆雌二醇浓度没有差异（P > 0.10）。对于具有两波或三波自发波发情周期的小母牛，在第13至22天期间，检测到P4浓度存在波×持续时间的交互作用（P < 0.01）。黄体期较高的P4浓度可能导致卵泡更新率更高或三波周期频率更高，而较低的P4浓度与两波周期相关。
