Relationships between the number of small follicles prior to superovulatory treatment and superovulatory response in Holstein cows.

In order to determine relationships between the number of small follicles prior to superovulatory treatment and superovulatory response, a total of 55 superovulations were induced in Holstein cows. The ovaries were examined ultrasonographically once 0-1.5 days before the initiation of superovulatory treatment. The number of small follicles 3-6 mm in diameter on both ovaries before superovulatory treatment was found to be significantly correlated with the numbers of corpora lutea after superovulation (r = 0.440, P < 0.001), total ova recovered (r = 0.503, P < 0.001) and transferable embryos recovered (r = 0.482, P < 0.001). These results indicate that a single ultrasonographic examination of follicles 3-6 mm in diameter prior to superovulatory treatment can be utilized to predict superovulatory response.