The gonadotropin compound, PG600, is used to induce estrus in prepubertal gilts, but responses can be variable. This study was conducted to evaluate PG600 effects on follicles, estrus, ovulation and estrogen production. Prepubertal gilts (n = 50) were treated with PG600. Gilts were evaluated for estrus while daily boar exposure was occurring. A sub-population of gilts (n = 12) were slaughtered on Day 3 to assess cytochrome P450 aromatase (CYP19) immunohistochemical staining in ovarian antral follicles. Ovaries of the remaining gilts (n = 38) were evaluated on Day 3 using ultrasonography and blood samples were collected for quantifying estradiol-17β. On Day 3 following administration of PG600, 94.0 % of gilts had large follicles, but only 76.3 % had expressed behavioral estrus by Day 6. Furthermore, 92.1 % of gilts had ovulations, with 16.6 corpora lutea/gilt. There was no association of number of large follicles on Day 0 or 3 with occurrence of estrus or ovulation (P > 0.05). Estradiol-17β concentrations on Day 3 did not differ (P > 0.05) in anestrus compared to estrual gilts and varied in gilts with large antral follicles. Immuno-detection of CYP19 on Day 3 was greater (P < 0.01) in large and medium compared to small follicles, (64.3 %, 34.2 % and 14.7 %, respectively). Results validate there is a dissociation of large follicle development with estrogen production on Day 3 in gonadotropin-treated gilts. These results indicate failure to express estrus may be due to follicle variation in estrogen production or response to estrogen feedback at the hypothalamus.

促性腺激素化合物 PG600 用于诱导青春期前小母猪发情，但反应可能会有所不同。本研究旨在评估 PG600 对卵泡、发情、排卵和雌激素产生的影响。青春期前的小母猪 ( n  = 50) 用 PG600 处理。在每天与公猪接触的同时评估小母猪的发情情况。在第 3 天屠宰小母猪亚群 ( n = 12) 以评估卵巢窦卵泡中的细胞色素 P450 芳香酶 (CYP19) 免疫组织化学染色。剩余小母猪的卵巢 ( n= 38) 在第 3 天使用超声检查进行评估，并收集血液样本以量化雌二醇-17β。在施用 PG600 后的第 3 天，94.0% 的小母猪有大卵泡，但到第 6 天只有 76.3% 的小母猪表现出行为发情。此外，92.1% 的小母猪排卵，每头小母猪的黄体为 16.6。第 0 天或第 3 天的大卵泡数量与发情或排卵的发生无关（P  > 0.05）。 与发情的小母猪相比，第 3 天的雌二醇-17β 浓度在无情期中没有差异（P > 0.05），并且在具有大窦卵泡的小母猪中有所不同。第 3 天 CYP19 的免疫检测更大（P < 0.01) 在大和中与小卵泡相比，（分别为 64.3 %、34.2 % 和 14.7 %）。结果证实，在第 3 天，在促性腺激素处理的小母猪中，大卵泡发育与雌激素产生分离。这些结果表明未能表达发情可能是由于雌激素产生的卵泡变异或对下丘脑雌激素反馈的反应。