The hardest time for a young bull is when it’s turned out with cows for its first breeding season after being well fed all winter.
Most bulls are confined after weaning and are fed high-concentrate feed for fast growth. Some have gone through bull test or feeding programs to measure rate of gain and feed efficiency and are overly fat.
Although most ranchers know fat is unhealthy for a bull, they still tend to buy the biggest, best-looking animals. Many breeders continue to overfeed because it’s harder to sell a bull that wasn’t pushed for faster gain.
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Fat bulls may not be as fertile if they have too much fat in the scrotum. Starchy rations can also cause permanent damage to feet.
Even bulls developed on growing rations usually carry more flesh than bulls raised on grass or wintered on hay. It can be a major adjustment when they are turned out with cows.
Some seedstock producers offer a feeding and wintering program, in which bulls sold in fall are kept, fed and then delivered closer to the breeding season.
Many bulls offered at bull sales have been overfed to some degree and confined during their growing months. Then they must suddenly adjust to pasture and breed cows. Even if they haven’t been overfed, they need time to make the transition.
“You want a bull with good growth potential, but not fat,” said John Kastelic of the University of Calgary. “The bull needs to be in reasonable condition, however, since young bulls lose a lot of weight during their first breeding season, especially on extensive range pastures where they have to travel. They can easily drop 200 pounds or more.
“You don’t want them going out thin, especially if they are breeding cows fairly early in the spring. Early grass is lush and green with high water content and not enough dry matter. Cattle may have fire-hose diarrhea from washy feed. Sending bulls out in good condition — not too thin and not too fat — is best, along with having them on a forage-based diet before you turn them out,” said Kastelic.
It’s best to keep bulls in a large enough area for exercise, to keep them in shape.
“Producers often winter their bulls in small pens with strong fences, then turn them out with cows into several sections of pasture, which is a huge adjustment,” he said.
Dr. Jennifer Pearson, assistant professor of bovine health management at the University of Calgary, said bulls need room to walk around.
“If they are standing around in feedlots and then we turn them out, they have a hard time handling it and can’t do the best job. They lose weight dramatically.”
Some people address this by using larger pastures with more distance to walk between feed and water.
Their feed should be transitioned as well, so rumen microbes can adjust to digesting and fermenting grass rather than grain, she said.
“If we don’t give them a chance to make a gradual change, or to adjust to the change before they go out, they may get sick or develop diarrhea because their digestive tract didn’t have a chance to adjust.
“We need to figure out ways to manage bulls prior to breeding, so they can be successful breeders and not fall apart during the breeding season.”
When putting bulls in breeding pastures, vaccinations and parasite control treatments must be up to date.
There are advantages to bringing a bull home a few weeks or months before breeding season so it can adjust to its new environment. Transport well ahead of time is also beneficial.
“When you transport a bull there will be stress,” said Kastelic. “When you stress a bull, you suppress the luteinizing hormone and it drops, taking testosterone down with it. With relocation there will always be some stress and decrease in semen quality.
“How long the decrease in semen quality persists depends on how anxious the bull is, how long the trip, etc. If you bring a yearling bull to a new farm and stick him in a pen with mature bulls and he gets beat up, he may have issues with semen quality for six weeks or more.”
Pasture management is another factor in helping bulls transition.
“Depending on how long your breeding season will be, you might have some flexibility. Maybe you have some pastures of modest size where you could do some initial breeding before you turn the cattle out on larger pastures — as opposed to turning them out on many sections of land, where the bulls have to travel farther,” said Kastelic.
A bull introduced to a pasture of fertile cows, where it only has to breed each cow once, will have an easier time in the breeding season.
“Try to have cows in proper body condition, with appropriate vaccination, to minimize infectious diseases and causes of reproductive losses,” said Kastelic.
“You need good management on the bull side, having him fit and ready to go, but you also need to optimize fertility on the cow side. This will minimize the number of times a cow might need to be bred before she settles. This makes it easier on the bulls and is also crucial to a sustainable operation.”
