Department of Animal and Food Sciences, University of Kentucky, Lexington, KY 40546-0215, USA.
Theriogenology. 2011 Jan 15;75(2):233-40. doi: 10.1016/j.theriogenology.2010.08.009. Epub 2010 Sep 26.
Holstein cows (n = 9) were used in an experiment to characterize the behavioral and endocrine responses to estradiol-17β when administered at rates designed to maintain peripheral concentrations within a physiological range. Cows were pretreated with progesterone for 3 d. Three days after progesterone treatment was completed, each cow was assigned to one of five estradiol-17β treatment groups (Doses 0 to 4), calculated to produce and maintain 0, 3, 6, 9, or 12 pg/mL in peripheral blood for 8 h. The experiment was conducted in eight replicates (with 3 to 7 cows each), with no dose repeated in any replicate. In each replicate, at least one additional cow was given an injection of estradiol-17β (500 μg im, in a corn oil vehicle) to facilitate estrus detection. Estrus was detected by visual observation for 30 min at 4 h intervals. Estrus was defined as a cow that stood to be mounted at least twice during the 50 h interval over which estrus was observed. Jugular venous blood samples were collected at 2 h intervals throughout the infusion and observation periods for quantification of luteinizing hormone (LH). Cows that received the highest dose (Dose 4, n = 7) all showed estrus, whereas those that received the two lowest doses (Dose 0, n = 5; Dose 1, n = 6) did not. Over the course of the experiment, five cows received each dose at least once. Of these, three showed estrus at Doses 2, 3, and 4, whereas the other two showed estrus only at Dose 4. Therefore, individual cows differed in the amount of estradiol-17β needed to induce estrus. There was a linear effect of dose on duration of estrus (P < 0.01). Estrus was shorter for Dose 2 (8.0 h) than for Dose 4 (18.4 h). The onset of estrus (after start of infusion) tended to be later for Dose 2 (20.0 h) than for Doses 3 and 4 (14.0 and 13.4 h, respectively; P = 0.15). Preovulatory-like surges of LH were induced in all cows at Doses 2, 3, and 4. Surges also were detected in 3 of 5 cows receiving Dose 1. The magnitude of the LH surge was less for Doses 1, 2, and 3 than for Dose 4 (P = 0.06). In contrast to the timing of estrus, the timing of the LH surge (after start of infusion) was not different among doses (P = 0.88). Thus, the hypothalamic centers responsible for regulating expression of estrus and secretion of LH responded differently to estradiol-17β.
选用 9 头荷斯坦奶牛进行试验，以研究当雌激素-17β 以维持外周浓度在生理范围内的速率给药时，其对行为和内分泌的反应。奶牛先用孕激素预处理 3d。在孕激素处理结束后的第 3 天，每头奶牛被分配到 5 个雌激素-17β处理组（剂量 0 至 4）中的一个，以在 8h 内产生并维持外周血中的 0、3、6、9 或 12pg/ml。试验共进行了 8 次重复（每组 3 至 7 头），每个重复都没有重复剂量。在每个重复中，至少有一头奶牛接受了 500μg 肌肉内注射的雌激素-17β（以玉米油为载体），以促进发情检测。发情通过每 4h 观察 30min 来判断。发情定义为在观察发情的 50h 间隔内，至少有两次站立接受配种的奶牛。在整个输注和观察期间，每隔 2h 采集颈静脉血样，以测定促黄体激素（LH）的含量。接受最高剂量（剂量 4，n=7）的奶牛均出现发情，而接受最低两种剂量（剂量 0，n=5；剂量 1，n=6）的奶牛均未出现发情。在试验过程中，至少有一头奶牛接受了每种剂量。其中，3 头奶牛在剂量 2、3 和 4 时出现发情，而另外 2 头仅在剂量 4 时出现发情。因此，个体奶牛发情所需的雌激素-17β量存在差异。剂量对发情持续时间有线性影响（P<0.01）。剂量 2（8.0h）的发情持续时间短于剂量 4（18.4h）。剂量 2 的发情开始（输注开始后）较剂量 3 和 4（分别为 14.0 和 13.4h）晚（P=0.15）。在剂量 2、3 和 4 时，所有奶牛均出现类似于促排卵前的 LH 激增。在接受剂量 1 的 5 头奶牛中，有 3 头检测到 LH 激增。剂量 1、2 和 3 的 LH 激增幅度小于剂量 4（P=0.06）。与发情时间不同，LH 激增的时间（输注开始后）在剂量之间没有差异（P=0.88）。因此，调节发情和 LH 分泌表达的下丘脑中枢对雌激素-17β的反应不同。
