Cow Heat Detection: Signs, AI Timing and Breeding Heifers

Updated: November 4, 2026

Missing a heat costs three weeks. Knowing the signs and checking twice a day makes breeding far more reliable.

Signs of heat

The surest sign is a cow standing still when another animal mounts her. Other signs: mounting others, restlessness, bawling, clear stringy mucus, a swollen vulva and ruffled tailhead hair. Heat lasts about 12–18 hours and comes back about every 21 days.

• Check at least twice a day, early morning and evening, for 20–30 minutes.
• Log every heat. Cowpanion predicts the next one.

Timing

For AI, the AM/PM rule works well: heat seen in the morning → breed that evening; heat seen in the evening → breed the next morning. With a bull, just log the date you saw them together.

Heifers

Most heifers are bred at about 13–15 months, once they reach roughly 60–65% of their expected mature weight. Breeding too small makes calving harder.

Pregnancy checks

A vet can confirm pregnancy by ultrasound from about 30–35 days or by palpation a little later. Log the result so Cowpanion can show the due date.

Keep it all in Cowpanion

Log each heat in Cowpanion and it predicts the next one, the pregnancy check day and the due date.

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This guide is general information, not veterinary advice. Always follow product labels and call your vet when an animal is sick.

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