A mare is most fertile during which period?

• A. Right before ovulation with LH peak
• B. Mid-cycle estrus only
• C. Immediately after ovulation
• D. During anestrus

Answer: (A)

Fertility in mares is highest as ovulation approaches. The surge in luteinizing hormone triggers ovulation, so the period just before this surge—and just before the oocyte is released—is when the follicle is mature and the timing is optimal for fertilization. At this time the uterus is receptive and sperm present in the reproductive tract have the best chance to meet the oocyte as it is about to be released, maximizing the likelihood of conception. Breeding earlier in estrus or after ovulation reduces the chances, and during anestrus there is no cycle or ovulation at all. So, the most fertile window is right before ovulation when LH is peaking and the egg is about to be released.