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.
The optimum age is 15 months or more. She should also be weighing at least 60% of the average weight of the main herd or the body weight of a mature cow that is comprised of similar breeding to her.She must also have good pelvic area and good capacity in her hips and barrel area before she can have a calf.eifers can be bred by the time they â¦ reach between 9 and 18 months of age, (preferably 15 months of age or older) and/or weigh 60% of the average mature cow-herd weight, since some heifers may not be able to be bred until they're ~20 months old, like with most Brahman heifers for instance.