Cows are in estrus (heat) for about 18 hours (range 6 to 30). The “Early Stage” is when you notice the cow is bawling and walking and butting, trailing, and mounting other cows, and has a swollen vulva with redness inside and little, if any, clear mucous discharge. Her cervix is open, and the uterus is rigid.

The “Middle Stage” is when the cow is complacent and restless, has a very red and swollen vulva with abundant and clear mucous discharge, and maybe slightly matted hair on the tailhead. As ovulation gets closer, she will continue to ride other cows and will begin to be ridden by other cows and then stands to be mounted (in standing heat).

The “Late Stage” is when the cow goes out of heat. She will continue to mount others and may still be ridden but will not stand. All signs of nervousness disappear, vulva swelling and mucus decrease, mucus becomes slightly rubbery, and the hair on the tailhead becomes matted. Ovulation occurs 14 hours (range 6 to 18 hours) after standing heat ends. About 24 to 48 hours after standing heat, she will have a slightly bloody mucous discharge.