Timing of Ovulation in Cattle

In all domestic animals, ovulation occurs during estrus. But in cattle, ovulation occurs:

Correct Answer: 12–14 hours after end of estrus

In cattle, ovulation is a post-estrus event — it occurs approximately 12–14 hours after the end of estrus (approximately 28–32 hours after onset of standing heat). This is unique and clinically very important for AI timing.

Clinical Significance

• Since ovulation occurs AFTER heat ends in cattle, inseminating during late heat or shortly after ensures sperm are present in the oviduct when the egg arrives.
• The 'AM/PM rule' in cattle AI: if heat is seen in the AM → inseminate in PM; if heat is seen in the PM → inseminate next AM.

Ovulation Timing by Species

• Most species (sheep, goat, sow, mare): Ovulation occurs during estrus (spontaneous, mid-to-late estrus).
• Cattle: Ovulation occurs 12–14 hr AFTER end of estrus ✔
• Bitch & Mare: Ovulate primary oocytes (not secondary oocytes).