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Nutrition and reproduction: Veterinarians discuss growth production and breeding soundness exam for young bulls

by Wyoming Livestock Roundup

In a recent Kansas State University (KSU) Beef Cattle Institute (BCI) podcast, dated Oct. 1, veterinarians from BCI highlight several options producers should consider as they focus on breeding soundness exams (BSE) in young bulls.

Phillip Lancaster, Bob Larson, Brian Lubbers and Brad White, all professors within BCI, discuss the importance of exams, growth perspective and changing diets, as well as forage quality, in addition to several other management tips for growing young bulls.

Issues in growing bulls

Larson discusses some of the issues with growing bulls and how these factors can affect the outcome of BSEs.

“The challenge with young growing bulls is they need to grow fast,” he explains. “They are big animals and they change a lot in weight between weaning and yearling age when we’re going to do their first BSE and get ready for their first breeding season.”

Larson explains, young bulls grow differently than growing heifers or maintaining cows in regards to the type of diet and quality of forage they need to grow appropriately. He also notes producers don’t want to underfeed or overfeed.

 “Bulls usually come to the sale pretty fleshy and there’s some negatives of this from a BSE standpoint,” shares Larson.

In addition, Larson says, “It’s really important the testicles are able to be cooler than the core body temperature. If there is fat deposition in the neck of the scrotum, it doesn’t allow the testicles to be cooler.”

 Fat deposition can lead to defects in sperm production and decreased fertility. 

“A lot of producers are used to seeing fat deposition, so they don’t see this as a problem,” Larson adds.

 “The other thing we see is lesions, particularly in the knees or other joints when young bulls are on an energy-dense diet,” he says.

Larson suggests completing a BSE on young bulls to determine their body condition and conduct a semen evaluation. He mentions there is a fine window for ideal growth in young bulls.

“I want bulls to grow fast, but not too fast,” he says. “I want them to be in good body condition, but not too good of a body condition.”

Achieving this can certainly be a challenge. Larson concludes, “It doesn’t mean bulls are going to fail their BSE and as a producing bull, but it could hamper their fertility.” 

Growth perspective and changing diet

             Lancaster discusses how producers can feed bulls to get them to grow efficiently without veering into acidosis: a buildup of acid in the bloodstream.

             “One of the things we want to think about is using some of our highest quality forages and byproducts that are high in energy, but low in starch,” Lancaster shares.

 Larson suggests using feed products such as distillers’ grains, corns, gluten feed and soybean wholes.

             “They have high energy, are high in digestible fiber and have very little starch, so we don’t run the risk of acidosis in those bulls,” Larson says, noting bulls will be eating a lot and producers will be pushing a lot of energy. “Producers may have to talk to their nutritionist to manage and formulate the right diet to get a rate of gain without over conditioning and running into subclinical acidosis issues.”

             “The beauty of cattle is they can eat feeds we can’t but the only reason they can is because of bacteria in the rumen,” White adds. “This is not just bacteria, but a lot of different populations that require time to shift.”

             “Whatever you’re changing in feedstuff, you really need to make that introduction slow and over time,” says Lubbers. “This is to allow bacteria in the rumen to adjust to new feed a little bit at the right time, and in return, will limit the risk of developing acidosis.”

Management tips

The team finally discusses several tips producers should keep in mind in growing young bulls and in performing soundness exams. 

The five tips for managing growing bulls include: formulate an appropriate ration and work with a nutritionist if needed, target appropriate body condition, not too fat and not too thin, manage feeding transitions slowly, use high-quality forages to decrease the amount of concentrate feeds needed and incorporate byproducts into the total ration.

             Brittany Gunn is the editor of the Wyoming Livestock Roundup. Send comments on this article to

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