BeefTalk: Developing sire genetic benchmarks

An Angus bull meanders along on a field on a Delaware farm on July 7, 2008.

Anyone who has raised a teenage boy knows that meeting his nutritional needs can be challenging because of the rapid growth his body is experiencing.

Just like teenage boys, young bulls also have special nutritional needs to optimize their growth and development, said the experts with the Beef Cattle Institute (BCI) at Kansas State (K-State) University on a recent Cattle Chat podcast.

“In developing bulls, it is important to think about the rate of gain and realize that bulls, because of their testosterone, can be fed more than a steer or heifer of the same age,” said Phillip Lancaster, BCI nutritionist.

A look into predicting bull fertility

However, a high-energy diet can cause challenges for the bull’s rumen if not introduced properly, Lancaster said. As one of the chambers in the animal’s stomach, the rumen can experience a pH imbalance leading to acidosis.

“Rumen acidosis is the decrease in rumen pH due to rapid fermentation of carbohydrates,” Lancaster said. In severe cases of acidosis, cattle will show signs of depression, loss of appetite and increased respiration rate.

“Whenever we change feedstuffs, it is important to introduce the new feed slowly over time to allow the bacteria in the rumen to adjust and reduce the risk of acidosis,” said veterinarian Brian Lubbers.

For growing bulls that will be eventually turned out on pasture with cows, Lancaster recommends feeding a high forage diet with some supplementation of feed that offers energy.

“We want to feed developing bulls our highest quality forages and then give them byproducts that are high in energy but low in starch, such as distillers grains, corn gluten or soybean hulls,” Lancaster said. “These feeds have high energy but because they have little starch, we lessen the risk of acidosis.”

Caring for first-calf heifers and calves

Lancaster and the other veterinarians also said it is important to keep the bulls in the optimum body condition to aid in fertility.

“Producers have a tendency to overfeed developing bulls to make them appear fleshy, but a bull with too much body fat can have fertility issues,” said veterinarian Bob Larson.

He explained: “It is really important for the testicles to be cool, which is why they hang down outside the body, but if there is too much fat deposition at the neck of the scrotum, then there can be defects with sperm production.”

Larson said oftentimes when defects appear under a microscope as part of a breeding soundness evaluation, body condition is one of the factors that veterinarians look to as a cause.

“It doesn’t mean that the bulls won’t breed cows, but rather they aren’t as fertile as they could have been,” Larson said. K-State Research and Extension

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