Genetic Hopes

Cattlelink - Genetic Hopes

Victoria G Myers
By  Victoria G. Myers , Progressive Farmer Senior Editor
Preventing illness in a herd requires good records and a veterinarian to advise on ways to avoid health problems. (Progressive Farmer image by Boyd Kidwell)

Four years after the Veterinary Feed Directive (VFD) began, it remains unclear how much of an inroad the statute-and-stick approach has made into U.S. livestock production systems.

The VFD, implemented in January 2017, moved antimicrobials away from over-the-counter sales to prescription or VFD status. Production claims related to their uses as growth agents were removed from labels. The most recent numbers from the Food and Drug Administration (FDA), released about a year ago, showed decreased levels in sales and distribution numbers of "medically important antimicrobials approved for use in food-producing animals." Tetracycline numbers, for example, decreased 40%. Overall sales and distribution attributed to cattle dropped 35% lower; the same decrease was recorded in swine. The chicken industry led with a 47% decrease.

Mike Apley, veterinarian and professor of production medicine and clinical pharmacology in the College of Veterinary medicine at Kansas State University, says the FDA report seems to indicate a dramatic drop. But, he says it's unclear how much of that was due to decreased authorizations for use, and how much was due to stockpiling prior to the VFD's implementation.

"We've seen some uses back up from 2018, chlortetracycline, for example," he says. "It continues to be hard to put cause and effect on the changes without the details. We don't have the data. I am personally aware of those who have altered use practices due to the VFD, but as to what extent that has happened industrywide, we can't prove that without data."

BRAND-BUILDING

The VFD and pressure to reduce antimicrobial use to comply with consumer marketing programs opened the door to a number of products, touted as options or even replacements, for antimicrobials.

A 2020 report from an emerging group, Lux Research, titled "Beyond Antibiotics: The Future of Animal Health Alternatives," considered three it described as "innovations" in the marketplace aimed at reducing antimicrobial use. Those innovations spotlighted included eubiotics, targeted antimicrobial agents and vaccines. Despite the new nomenclature, none are actually new to the world of animal agriculture.

The report theorized COVID-19 raised awareness of antimicrobial resistance. The Lux analysts, who did not respond to requests for interviews, wrote: "COVID-19 has pushed animal health back into the spotlight due in part to human infections affecting processing capacity and increasing awareness around value chain transparency. The livestock industry will be driven to take greater measures to protect the value chain, including tracking the where, when and how of livestock management, production and processing. This adds momentum to antibiotic alternatives and tech that improves and tracks livestock welfare."

The group says as a result of this "greater transparency" and COVID-19's added pressure on the industry, there will be opportunities for new technology supporting livestock welfare moving forward. Specifically, they note probiotics, prebiotics and vaccines as strong in the area of disease prevention; bacteriophages for disease treatment; and probiotics and phytogenics for growth promotion. But, antibiotic alternatives, they write, are at an early stage of adoption and "uncertainty reigns."

KSU's Apley says none of the "innovations" in the Lux report are new to animal agriculture. Antimicrobial peptides, for example, were going to save the world back in 1992, he recalls. "Thirty years later, we do have some peptide antibiotics, but all of that hope hasn't come to fruition. Today, finding an antibiotic alternative that has anywhere near the efficacy of an antimicrobial is something we hope for. It is not a reality."

Asked why there aren't more clinical trials to provide third-party reviews of potential therapies, Apley explains while there is a suite of various products that might impact cattle immune systems and in some way boost disease resistance, these products only create part of the effect of one good antimicrobial. The cost to develop and approve these products runs into the millions, "and the bang for the buck, unfortunately, is not that of antibiotic use. Everyone has a press release that says, 'Here's the next greatest thing,' and in some cases, we see small studies that seem to confirm efficacy. But, there is difficulty showing that response on a larger scale."

Apley says we shouldn't take this to mean that none of the optional treatments work. They might. But, they are going to be fighting an uphill battle in terms of acceptance.

"Expectations for any alternative treatments tend to be based on what producers are used to seeing after treating with an antimicrobial," he explains. "We are accustomed to the dramatic effect we see when a long-acting antibiotic is used on something like foot rot. She's up and walking, and that's the effect we want to see. Many of these alternative treatments are more subtle but just as costly. That is the reality today. I hope someday we can see products that will completely prevent disease or wipe out a bacterial infection without selecting for resistance, but we don't have that now. Today, anything that has an effect, bacterially, will also select for resistance. When you are talking about trillions and trillions of bacteria, there is always eventually going to be a mutation, and resistance will develop over time."

Apley stresses while he may look at treatment options with a critical eye, he has no doubts when it comes to the reality of antibiotic resistance.

"Antibiotic resistance is real," he says. "The last time a new family of antibiotics was introduced in food animals was in 1978."

In cattle with respiratory disease today, he says he expects to see a 70 to 80% positive response to treatment with a long-acting antibiotic given a five- to seven-day interval to respond. Those respiratory diseases in previously treated calves are resulting in a 5 to 10% death loss.

GENETICS MAY BE THE KEY

What if instead of treating that cow with foot rot, she were culled? For that matter, what if producers culled much more aggressively overall for health problems? Would that make as much of an impact as alternative treatments and ultimately lead to less need for treatment of any type?

Apley says there's a lot of possibility in this approach, but he believes it might be a bitter pill, with purebred winners and losers in the cull approach.

"We are seeing this play out right now in Canada, where they are using a predictive factor in dairy bulls to cull females against mastitis. We know today that health heritability is higher than we thought," he explains. "My hope is eventually when we look at EPDs, there will be one for health. But, it will take a shift in mindset in some cases. If you tell a cattle producer to cull around something, you are essentially insulting that herd. You are telling him it's not perfect the way it is. So, it's almost like an intervention that has to happen. That said, I really do think looking to the future genetic selection is the key."

A grant project through the International Consortium for Antimicrobial Stewardship in Agriculture (ICASA) is currently looking at identifying potential cases of late-day bovine respiratory disease (BRD) in high-performing feedlot cattle­, and it is possible a genetic role is at work. The Noble Research Institute, a founding member of ICASA, reports it is a grant partner with Hy-Plains Feedyard, Veterinary Research and Consulting Services, U.S. Meat Animal Research Center and the Great Plains Veterinary Educational Center on this project. While the data is not in, one consideration going into the study was whether there is a genetic element.

Myriah Johnson, a former agricultural economics consultant at Noble, notes cow/calf producers have selected for high-performing cattle, and they are characterized by high average daily gain and improved feed conversion. They yield a valuable carcass based on carcass weight, yield grade and quality. But, an increased incidence of BRD has been observed at 60 to 90 days in these high-performing cattle. Despite advancements in technology and genetics, morbidity and mortality continue to increase in the feedyard.

Johnson says the grant project will look at the effect of rate of gain and length of backgrounding on the health and performance of calves. More data analysis will be done on vaccinations and timing, along with an evaluation of genetics, feed intake and physiological responses of these cattle.

"We are only at the tip of the iceberg with this and hope to learn much more that will guide further research," she says.

MANAGEMENT CONSIDERATIONS

Part of seeing a successful outcome when treating a sick animal is having a plan. Apley advises producers to evaluate the overall herd and, if a large percentage of calves are ill, to reassess treatment protocol.

"Look at the success rate for the treatment you are using and the fatality rate. To do that accurately means you have to keep good records. It is amazing how many good decisions you will make when you have a good recordkeeping system to back them up," he says. "It's easy to just switch drugs when you feel things aren't going well, but if I start changing drugs up frequently, that impacts my ability to accurately evaluate, and ultimately improve on, my management system."

Along with good records, there are other ways producers can improve herd health and stop the spread of antimicrobial resistance. The first key is to have a good relationship with the herd veterinarian. Ask for preventive advice not just a treatment. Good husbandry is the key to a successful outcome, along with biosecurity practices, fly control, good nutrition, vaccinations and overall worker and facility cleanliness.

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