Factors affecting superovulation in heifers treated with PMSG.

Area of Science:

• Reproductive biology
• Veterinary science
• Animal reproduction

Background:

• Superovulation protocols are crucial for maximizing embryo yield in cattle breeding programs.
• Pregnant mare serum gonadotropin (PMSG) and purified follicle-stimulating hormone (pFSH) are commonly used gonadotropins for superovulation.
• The timing of gonadotropin administration relative to the estrous cycle can influence ovulatory response and embryo recovery.

Purpose of the Study:

• To evaluate the effect of PMSG immunoneutralization on ovulatory response, follicle development, and embryo yield in superovulated heifers.
• To determine if the stage of the estrous cycle at PMSG injection impacts ovulatory response and embryo yield.
• To compare the efficacy of PMSG alone, PMSG with Neutra-PMSG, and pFSH in superovulation protocols.

Main Methods:

• Estrus was synchronized in heifers using a prostaglandin F2alpha (PG) analogue.
• Heifers received treatments including pFSH, PMSG, or PMSG followed by Neutra-PMSG.
• In a separate experiment, PMSG was administered on different days of the estrous cycle (Day 2, 3, 10, or 16).

Main Results:

• PMSG administration resulted in a greater number of ovulations and large follicles compared to pFSH in one experiment.
• Neutra-PMSG did not improve embryo yield or quality (Grades 1 or 2) but decreased Grade 3 embryos.
• Ovulation rate and embryo recovery were significantly reduced when PMSG was administered on Day 3 of the estrous cycle compared to other days.

Conclusions:

• Immunoneutralization of PMSG with Neutra-PMSG did not enhance embryo yield or quality in superovulated heifers.
• Administering PMSG early in the estrous cycle (Day 2, 10, or 16) can lead to acceptable embryo yields.
• Sufficient time between PMSG treatment and luteolysis is important for optimizing embryo yield in superovulated heifers.