However, large, heavy bulls should not be used because they can injure young heifers or small cows when they mount them. Many producers use Jersey bulls because of their small size. Be aware though, that any breed of bull, particularly dairy bulls, can become aggressive and need to be handled with caution. Gomer bulls do make good heat detection aids because they are naturally adept at identifying cows in heat. Androgenized cows are females that been given the male hormone, testosterone, to stimulate them to show male behavior.
Androgenized cows are often safer to work around than gomer bulls.
Producers may choose a cow that can no longer produce calves, is a poor producer, or is a freemartin heifer. Select a good-sized female that will not be dominated by the larger cows in the herd. This involves administering testosterone to the cow. There are two basic ways to accomplish this. The second method is a little simpler, and the androgenized effect persists for approximately 90 days.