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.
1 You will always know when a heifer or cow is ready to be bred when they go into heat. 2  Normal estrus periods last 24 hours and occur between 17 to 24 days. 3  The better condition score a cow is after calving, the sooner she'll be ready to breed.epending on the breed of the heifer, most heifers will start to show the first signs of heat when they are between 9 and 22 months of age. 1  The rate of sexual maturity or puberty is determinate of genes and breeding.