Most form pairs during the breeding season, but in some species, such as fur seals, the gray seal (Halichoerus grypus), and elephant seals, males (bulls) take possession of harems of cows and drive rival bulls away from their territory.
Look for the crooked tail. This is probably the best ways to tell if a cow has been bred: A cow or heifer will have a crooked tail or a tail that is held out in an odd angle than usual for 24 to 48 hours after being serviced by the bull. 1  4 Edit step.
Know the physiological reproductive cycle of cattle. Cows and heifers typically go into heat or estrus every 17 to 24 days (average is 21 days). A bred cow or heifer will usually not go into heat until a few weeks after giving birth. 2. Know the behaviour changes of cows and heifers going into heat.