Placing two or more bulls in the same breeding pasture creates both efficiencies and problems. Dr. Robert Wells, a consultant with the Samuel R. Noble Foundation in Ardmore, Okla., said the practice is common, especially for larger herds in a commercial situation. “It’s easier to manage your operation when you’ve got less breeding units and more animals in the same pasture,” Wells told Ozarks Farm & Neighbor.
Competition between the bulls is likely, but can be minimized by how the bulls are managed prior to the breeding season. Wells said new bulls should be introduced into the mix before the breeding season, so they have an opportunity to establish the dominance order at that time. It also reduces the potential for injury from fighting during the breeding season, so they can become familiar with each other without the complicating presence of females in heat.
Age plays a role in the establishing hierarchy: Wells said, “Typically, the older, more mature bulls are going to be larger, more massive framed and more developed. So older bulls are going to be your more dominant bulls within reason; a 10 or 12-year-old bull is probably losing muscle mass, and he may be a little more feeble than a 4 or 5-year-old bull.”
Some research has indicated the dominant bulls will get more females bred in a breeding season than will the non-dominant bulls; that’s one reason Wells recommended putting an odd rather than an even number of bulls in a breeding pasture. He explained, “If you have two bulls that want to just fight it out all the time, that third bull in the pasture is getting the job done while the other two are trying to establish who the more aggressive, dominant bull is.”
Wells said he tells his clients to supply one mature bull for every 20-25 cows in the pasture, taking into account variables like pasture size and topography, and how narrowly defined the breeding season is. For younger bulls, the rule of thumb is one cow for every month of age of the bull starting at 16 so, for instance, a 17-month-old bull would be able to handle no more than 17 cows during a defined breeding season. Fewer bulls are needed for a 365-day season, but for a 45-day season the ratio may be reduced to less than 20 cows to the bull, to ensure every cow that comes in heat has the opportunity to be serviced at least twice during the breeding season.”
Eldon Cole, University of Missouri Extension regional livestock specialist, said if the pasture and number of cows are large enough two or more bulls may be needed, but not necessarily at the same time. “If you want to get maximum use out of the bull, rotate them in one at a time; in a week or 10 days, put a new, fresh bull in,” Cole told OFN. “For the most part, if you have a large enough pasture, they’re going to take each group of cows off to themselves, and they can get along quite nicely.” But the dominant bull will likely breed a majority of the cows, “and if you’ve got more than two bulls out there, one bull may not breed a single cow.” It may be advantageous to have bulls of different breeds in the same pasture, so you can identify the sire of the calves by color without a DNA test. However, “I think as we have had a pretty good run now with calf prices, people are considering DNA testing to find out which bull is getting calves 40 or 50 pounds lower at weaning than a set of calves out of another bull.”
