“Everyone understands that we need to properly prepare cattle on the ranch of origin through preconditioning. But, if you get rid of metaphylaxis in high-risk calves, we will see an increase in sickness and death loss, with no proof that we will decrease antibiotic resistance,” says Dan Thomson, DVM and Jones Professor of Production Medicine and Epidemiology at Kansas State University (KSU).

That’s too easy to gloss over in an age when so much discussion revolves around antimicrobial resistance (AMR) in humans and the potential contribution of antibiotic use in livestock.

If metaphylaxis were eliminated in the U.S. cattle industry without suitable health management alternatives, it could cost that industry as much as $1.8 billion annually, according to a KSU analysis of the economic impact of treating groups of high health-risk animals with antimicrobials.

“We know that if metaphylaxis were not available, a reduction in revenue would result from reduced average daily gains, increased feed conversions, higher health costs from treating more sick animals, more deaths primarily for those high health-risk animals, among other factors,” says Elliott Dennis, a KSU doctoral student who worked on the study.

Production and health management data for the study came from 10 large Midwest feedlots for cattle classified as high health-risk and administered an antimicrobial upon entering the feedlot. Although the numbers would be different, logic suggests the same production metrics would decline for stocker operators.

Ted Schroeder, a livestock economist and KSU distinguished professor of agricultural economics, adds that removing metaphylaxis or any animal health management technology from feedlots has a snowball effect.

“A lot of that direct cost would be absorbed by the feedlot, but a very significant amount of it would go back to cow-calf producers who are supplying calves,” Schroeder explains. “Even if they are supplying healthy calves, they are still going to be influenced because overall the feedlot sector’s costs get passed down because they are a margin-taker.”

Economic losses ultimately would catch up to the consumer, too.

“That reduction in profitability would then be passed up and down the beef supply chain, ultimately resulting in higher prices for consumers to pay for beef at the supermarket,” Dennis says.

Facets of antimicrobial resistance

The jury is still out on whether or not the use of antibiotics in livestock production can impact AMR in humans.

For instance, pioneering research at Colorado State University (CSU) found bacteria that had antimicrobial resistant genes (AMR) in the feedlot where cattle were fed (feces), on the trucks that hauled them, in water of holding pens and at the packing house.

But, according to Keith Belk, holder of the Ken and Myra Monfort Endowed Chair in Meat Science at CSU, “In this particular study, with the sensitivity available to us, we couldn’t find a single, solitary AMR gene in the meat product leaving the packing plant, going to consumers.”

That’s not saying there are none. It does suggest that meat from cattle receiving antibiotics, as a conduit to passing along resistance to humans, is negligible.

In other research, Belk says antimicrobial resistance in cattle administered metaphylaxis was no different 26 days later than before treatment.

“If we treat cattle with an antibiotic, we’re going to take the population of bacteria that are in their gut and in the feces outside of their gut in the pen, and we’re going to modify them by selectively killing the bacteria susceptible to the antibiotic,” Belk explains. “We’re going to leave all of the bacteria that are resistant to the antibiotic.

“So, when I give a metaphylactic treatment, I create a microbiome that has a higher prevalence of bacteria that carry genes resistant to the antibiotic. But within 15 or 20 days, the microbiome returns to the way it was before.”

See the BeefVet article, Inside-Out Revolution for more information about the research efforts of Belk and his peers in the nascent field of microbiome modulation.

On the other hand, there is a correlation between antibiotic use in livestock and subsequent AMR in livestock disease pathogens. While Thomson believes large data sets are too easily confounded to say with certainty that antimicrobial-resistant pathogens are increasing in the beef cattle population, he recognizes producers have little choice other than using macrolides for both metaphylaxis and treatment.

Plus, Thomson believes producers have limited incentive to test cattle for AMR pathogens.

“It’s so expensive to submit samples to a diagnostic lab for what you get back (around $150), “Thomson says. “We only have four or five antibiotics to choose from, and how do we know the pathogen won’t be resistant to the next one, too?”

When diagnostic testing is utilized, Thomson cautions about understanding how to use the data. For instance, if you submit samples only in the middle of a health wreck, and the samples are from calves already treated multiple times, finding AMR shouldn’t come as a surprise. Conversely, if samples are regularly submitted in the course of regular management protocol, apparent AMR trends may carry more weight.

“Work with a veterinarian to understand the different classes of compounds, and make sure you’re using them according to label directions. We don’t have problems when we do that,” Thomson says. “Cattle health, antibiotic stewardship, sustainability, it all goes back to people doing the right thing.”