Breeding season bull management

South Dakota State University Extension

 As breeding season gets underway there are some points to remember about the bull battery.  The most economically stable ranches are those that get cows and heifers bred early in the breeding season.  The two key factors in making this happen are that the female is cycling and the bull is in proper condition.  If we assume the bulls are in proper body condition score, have had adequate exercise, and have been with the other herd bulls to determine social dominance, we should be able to turn them out and forget about them, right?  No, as ranchers you need to continually observe and manage bulls.
Young bulls have great potential to bring genetic improvement to your herd, however they will experience an acclimation period prior to breeding any females.  In order to start calving on your selected date, it may be important to turn young bulls out a few days early, so they can get adjusted to their environment and be ready to breed cows when you would like them to start.  Another key point with young bulls is to have three or more bulls per pasture, as this helps increase sexual activity.  If only one yearling bull is put in a pasture, there may be decreased early season conception rates, having a negative impact on overall calf crop.
Social dominance in pastures can be a concern. Make sure that yearling bulls and older, mature bulls are in separate pastures.  If they are together, the yearlings cannot compete with the older bulls and may get cows bred, resulting in limited genetic improvement, as well as possible injury to the younger bulls.  If older bulls have been used more than two breeding seasons, they have a tendency to become territorial and may spend more time fighting and defending their territory than servicing cows.  This is another situation where observation is key, not only because they may not be getting the cows bred, but because they could be injured or causing injuries.  Work to group bulls together that will minimize this negative behavior.
When determining which bulls to group together, the next important question is how many bulls to put in each pasture.  The traditional rule of thumb has been 25-30 cows per bull, however, there has been research that indicates this number could be increased to as many as 50 cows per bull without a negative impact on conception rate.  However, a breeding soundness exam must be done 30-60 days prior to bull turn out.
When determining proper bull power, there are three factors for each ranch to consider.  First, what is the topography, feed condition and pasture size?  There is evidence that the cow finds the bull, however if the pasture is hilly, has a lot of vegetation, or in the case of western South Dakota, is very large, this limits the number of cows that a bull will be able to service.
Secondly, is to consider the age and condition of the bulls.  Young bulls will be more challenging because they are still growing.  They have higher nutrient requirements and therefore will lose condition faster than mature bulls.  This may be a situation where young bulls are rotated in groups for shorter periods.  The maximum time to leave yearling bulls with cows is 70 days, but shorter is better.
Finally, the length of the breeding season and the amount of observation is critical.  Ideally, a 60-90 day breeding season is best to ensure similar calf ages and weights at weaning.  Ranchers need to observe bulls for mating desire as well as physical injuries.  If you are observing animals closely, bulls that are either injured or lack desire can be removed.  Research in Texas and Colorado indicate that one in five beef bulls is questionable or unsatisfactory as a breeding bull, so don’t be surprised if the bulls are not performing as you would expect.
Source: Adele Harty


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