What is a common sign that a cow is in estrus?

• A. Lying down.
• B. Increased appetite.
• C. Tail wagging.
• D. Standing heat (cow stands to be mounted).

Answer: (D)

When a cow is in estrus, she shows standing heat—the moment she will stand still to be mounted. This behavior is the clearest, most reliable sign of readiness to mate because it directly indicates receptivity to mating. Other common behaviors, like lying down, increased appetite, or tail wagging, are not specific to estrus and can occur for many reasons, making them poor indicators on their own. Standing heat is what farmers use to time artificial insemination, since it marks the exact window when ovulation is approaching.