Abstract
In order to clarify the individual follicular development during superovulation treatment in Japanese black cows, consecutive ultrasonography was performed. A total of 5 cows was superovulated in mid-luteal phase. Ovaries were monitored with ultrasonography at 12 h intervals from the initial FSH injection (=0 h) until 24 h after the first ovulations. All follicles more than 5 mm in diameter were determined in freezing ultrasonography images with built-in calipers. Blood samples were collected at 12 h intervals for 168 h and the concentrations of progesterone and estradiol-17β were determined. Few follicles more than 5 mm in diameter emerged at 12 h after FSH injection, but most follicles more than 5 mm in diameter emerged at 36 h. Then, these emergence tended to decrease gradually. Every ovulatory follicles were retrospectively identified more than 5 mm in diameter at 84 h. The follicles that emerged later tended to grow faster than those emerged earlier within 84 h after treatment. The progesterone profile after prostaglandin F2α (PG) injection in superovulated cows was similar to those in normal cycling cows synchronized with PG. The estradiol-17β profile showed a slight increase between 0 and 72 h during the follicular growth, then the levels reached peaks in accordance with estrous behavior prior to a sharp decrease before ovulation.
