Livestock: May 2005

OK, you've spent $50 on your bull's breeding soundness examination, and he's good to go. Or, maybe he's already out earning his keep in your spring-calving herd. Many things can go wrong, however, during a 60-90 day breeding season, so now is not the time to let him go unsupervised. It is good management to observe him regularly to make sure he's still willing and able to do his job. I recommend watching him in action during the breeding season. Obvious physical problems that may have arisen since turn-out can be detected and addressed, like lameness or injury. Another simple thing to do is record the numbers of the cows and dates he services them, then find those cows in 18 to 23 days to make sure they are not coming back into heat. That, of course, would indicate he may have become infertile and you could address it in a timely manner.

Dr. Glen Selk at Oklahoma State University has authored a great fact sheet (#F-3254) concerning the management of beef bulls before, during and after the breeding season. It is an excellent reference and can be printed off OSU's Web site at: http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-1922/F-3254web.pdf.

One key concept he discusses is social ranking or dominance in multi-sire herds. Dominant bull(s) will breed more cows compared to less-dominant bulls, especially when older and younger bulls are used together. In an Australian study, the dominant bull of a four-bull group sired 70.4 percent of the calves. The remaining three bulls, a 4-year-old, a 3-year-old and a 2-year-old, sired 16.7 percent, 7.4 percent and 5.5 percent of the calves, respectively, in the first year of a five-year study (see Figure 1). As you can see, dominance changed over time, but the dominant bull always sired most of the calves.

Using bulls that are roughly the same size and age can minimize dominance. Also, since dominant bulls work harder, they will lose condition quicker. Rotating these bulls out of the herd for a week or two of rest and added nutrition is one way to deal with this situation, and it gives the less-dominant bulls more chance to do their share. Another approach is to start the breeding season with older bulls and replace them with the younger bulls later.

Rotation can also be used simply to maximize the use of a bull battery made up entirely of young bulls. According to Dr. Selk, "rotating them at a minimum of two weeks will allow for optimum reproductive performance and not allow young bulls to become too fatigued or lose condition too rapidly. If pasture and management capabilities allow, rotating young bulls once per week should slightly improve reproductive performance..."

Bulls need to be managed and provided for all during the year, but especially during the breeding season. It's too important to just turn them out and forget about them ? your next calf crop may be at stake.