Research links cattle diet and shipping fever

News
Dec 3, 2010
by WLJ

A carefully timed diet high in roughage like hay may well reduce the incidence of bovine respiratory disease, also known as shipping fever, scientists reported last week.

The team says that reducing the spread of the pneumonia-like infection could lower the need for mass inoculations of antibiotics just as the young calves are moved from pasture to feed yard.

The scientists—led by Michael Galyean of Texas Tech University’s (TTU) Department of Animal and Food Sciences, and Jeff Carroll of the USDA-Agricultural Research Service (ARS) Livestock Issues Research Unit at Lubbock— developed a technique to mimic the effects of the respiratory disease by creating an inflammatory response and elevated body temperature in experimental cattle.

“Shipping fever is the No. 1 economic problem for the industry,” said Galyean, TTU’s Thornton chair in beef cattle nutrition and management. “Anytime these animals get this disease, there are long-term consequences, including lung scarring and decreased performance. Anything you can do to slow or prevent this disease is a good thing.” Creating a solution In the two-year cooperative research effort, Galyean, Carroll and Ryan Reuter, a TTU doctoral student, intensely examined typical management practices used to control shipping fever. Injecting cattle with lipopolysaccharide, a component of bacterial cell walls, to temporarily but safely produce an immune system response linked to body temperature in the cattle, the scientists evaluated six treatments that were combinations of dietary energy level and antibiotic therapy.

In the study, researchers used 24 500-pound calves from the Noble Foundation, an Ardmore, OK-based non-profit agricultural research organization.

“Previous energy intake of those animals had an effect on body temperature,” Galyean said. “If they were eating a higherenergy diet such as one high in grains, then they had a more intense fever response. That helps explain what cattle owners have observed in their feedlots.”

Animals that have a more intense fever response tend to display disease characteristics early, including fever, nasal discharge and pneumonialike symptoms, and are more likely to be pulled for treatment. “We’ve suspected that for awhile, but these data actually back that up,” he said.

Another aspect of the study found that the source of energy, whether it’s roughage or grain, does seem to make a difference in the ability of the animal to deal with the disease challenge, said Carroll, research leader with the USDA-ARS research unit. The findings can potentially help feedlot operators determine what kind of diet they might want to feed.

“There may be some actual immunological merit to feeding a higher roughage diet for a longer period of time than they currently do before shipping and shortly after arrival at the feed yard,” he said.

The work was funded by a cooperative agreement between TTU’s Department of Animal and Food Sciences and the USDA- ARS Livestock Issues Research Unit.

Typically, shipping fever is seen in feeder calves seven to 21 days after arriving in a feed yard. But the disease actually starts developing as cattle are weaned and transported into the production system, typically when they are shipped to feed yards. During the period, the cattle often experience compound stressors such as weaning coupled with being commingled with new animals.

This stress suppresses immune functions so that the cattle become more susceptible to viral infections.

These infections, which are harsh in themselves, can lead to more troublesome bacterial infections. That’s when bacterial pneumonia, which is the classic definition of shipping fever, enters the picture.

Every year, hundreds of thousands of cattle are weaned, sold in auction markets and transported varying distances. Depending on the circumstances, the percentage of shipped cattle that become clinically ill ranges from zero to more than 50 percent.

Traditionally, cattle producers have attacked the respiratory disease problem in two ways. One, intervene with a vaccination and preconditioning program before the cattle are even shipped. Two, apply effective but costly mass treatments of antibiotics to the animals when they arrive at their shipping point.

In the past quarter century, researchers examined disease reduction through nutritional treatments to improve the animal’s health. Diets that are higher in roughage tend to reduce susceptibility to respiratory disease, but come with a side effect of reducing weight gain. — WLJ

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