By the beginning of April, most cow-calf producers in the Southern Great Plains are a few weeks away from the start of the breeding season and are wrapping up routine preparation of bulls before turn-out. Ideally, bulls are in a body condition score of at least 6.0 to 6.5, maintaining their condition on a high-forage diet and getting plenty of exercise. They have received immunizations and parasite control, and passed a complete breeding soundness examination. All this preparation is critical, but it is not the end of the manager's responsibility. Throughout the breeding season, managers need to observe and address health issues and physical problems that may arise, and manage the hierarchy of social dominance among the bulls. This is true if your herd has two bulls or twenty bulls.
Dr. Glenn Selk, Oklahoma State University emeritus extension animal scientist, authored an outstanding publication, Management of Beef Bulls, covering all aspects of bull management. At the bottom of page five in this publication is a table that illustrates the effect of bull dominance over time.
The data emphasizes two basic facts: the dominant bull in a breeding herd sires the greatest percentage of the calves, and, up to a certain point, age is a primary factor in determining dominance.
Many producers have herds of 50 or fewer cows and only two bulls. Dominance is just as much an issue for smaller herds as for larger ones. Here is a common scenario for small producers:
The producer has 40 cows, an older bull (A) and a younger bull (B) getting ready for his first breeding season. The bulls are run together in the off-season. When the breeding season comes and cows are returning to heat in large numbers, how does the rancher manage his two bulls?
We recommend turning both bulls out together. Bull A's dominance, experience, maturity and capacity will enable him to settle the largest number of cows early. Remove bull A from the breeding pasture to rest after a month, or earlier if he drops a full body condition score. Leave bull B alone with the cows for at least two weeks, and for the rest of the breeding season if his body condition stays above a score of 5. It is critical to favor this young bull during his first breeding season. Turn bull A back out with the cows after bull B has had his two-week learning experience. By the end of six to eight weeks, the majority of the cows should be settled. Both bulls can "clean up" for the rest of the breeding season, assuming the young bull has regained condition.
When only one or two bulls are used, it is vitally important to observe them in action throughout the breeding season. Make note of the cows' IDs and service dates, then find those cows in 18 to 23 days to make sure they don't return to heat. If bull A in the scenario above became infertile after two weeks, you would know it and could remove him from the breeding pasture. If undiscovered, he would still exert his dominance over B and cows would go unsettled or breed later in the season.
In small herds, observation during the breeding season and management of social dominance among bulls is just as important to success as fertility, health and physical soundness.