Which hormone is used first in the superovulation protocol described for producing gene-targeted animals?

• A. hCG
• B. PMSG
• C. Both hormones together
• D. No hormones

Answer: (B)

The first step in a superovulation protocol for producing gene-targeted animals is to stimulate multiple follicles to develop. This is achieved with PMSG (pregnant mare serum gonadotropin), which has FSH-like activity that recruits and grows many ovarian follicles. After an appropriate interval, hCG is given to mimic an LH surge and trigger ovulation of those mature follicles. Therefore, the first hormone used is PMSG. Using hCG first wouldn’t promote follicle growth, giving both together isn’t the standard sequence, and giving no hormones wouldn’t produce the increased oocyte yield needed.