Antibiotics

9 Questions to Guide Antimicrobial Selection in Cattle

Tue, 24 Feb 2026 19:11:39 GMT

In bovine practice, smarter antimicrobial selection starts by asking better questions. Antimicrobial stewardship isn’t necessarily about using fewer drugs, but using the right drugs for the situation. Dr. Corale Dorn, owner of Dells Veterinary Services in South Dakota, suggests asking the following nine questions before reaching for a bottle.

1. What Pathogens Are We Treating?

“You’ve got to get the diagnosis right before you pick what antibiotic you’re going to use,” Dorn says.

Antimicrobial selection in cattle must begin with pathogen clarity.

Is this truly bacterial disease? And if so, what are the most likely pathogens? A navel infection differs from respiratory disease just as uterine pathogens differ from central nervous system pathogens.

“We’re super lucky that people will bring the sick animals to us … so we have the opportunity to do a very thorough physical exam,” Dorn says. “We want to get that diagnosis right, or at least a good list of differentials, and we’re thinking about some of those comorbidities.”

Before selecting an antimicrobial, narrow your differentials and identify the organisms you are most likely targeting. Stewardship starts here.

2. Is There Something Labeled We Can Use?

Start with labeled products whenever possible.

Is there an antimicrobial approved for this disease in this species? Labeled use strengthens regulatory compliance and simplifies withdrawal considerations. Extra-label drug use may be necessary, but it should follow a clear rationale, be well documented and be founded on a valid veterinarian-client-patient relationship.

3. Is There Any Medication We Cannot Use?

Antimicrobial selection is as much about exclusion as it is about selection.

Are there legal restrictions? Are certain drugs prohibited in food animals? Do extra-label drug use regulations eliminate certain options?

Removing inappropriate options early protects both the patient and practitioner.

4. Can We Reach the Pathogen Where It’s Living With This Drug?

Pharmacokinetics and tissue penetration should drive decisions.

“There’s lots of things out there that are labeled for Histophilus somni in cattle to treat it. However, if it’s in the brain and it’s causing TEM, is that drug going to be able to penetrate through the meninges?” Dorn asks.

Drug labels and spectrum charts are helpful, but drug distribution determines success. Lung tissue, uterus and central nervous system each present different barriers.

Dorn explains often the question posed is whether bacteriostatic or bactericidal antibacterials are better. In the past, students were taught bactericidal was best, but recent work suggests that it doesn’t really make a difference.

“Can that drug get to that location is more important,” Dorn says. “It doesn’t really make a difference whether it’s static or cidal as long as we’re giving support to the animal.”

5. Can We Even Get That Product Right Now?

Dorn has an all too familiar question she has to ask: “Is it even on the shelf this week?”

Ideal protocols mean little if the drug is unavailable.

“The supply chain business is just infuriating. You get it down to your favorite protocols, and then that’s not available anymore,” Dorn says.

Drug shortages and supply variability have become part of production medicine. Understanding drug classes and alternatives allows flexibility when inventory shifts.

6. What Are the Milk and Meat Withdrawals?

Withdrawal times are central to antimicrobial use in cattle.

How long are milk and meat withdrawals? Does this animal’s stage of production make those intervals critical? Is she close to market? Is she a high-producing dairy cow?

Withdrawal considerations affect economic decisions and regulatory compliance.

7. How Many Treatments and How Easy Is the Treatment?

“You’re thinking about how many treatments this is going to take and how easy it is to give the treatments in this particular case,” Dorn says, acknowledging each operation is different. Daily restraint in a well-designed dairy parlor differs dramatically from catching pasture cows multiple times.

Communicating the impact of the individual operation with your client is also important.

“It never fails,” Dorn says. “You give a treatment, and they say, ‘Oh, that’s not what you gave my neighbor’s cow last week.’”

Treatment protocols must fit the production system, not just the pathogen.

8. How Much Does It Cost?

Drug choice influences not only treatment success but also labor costs, compliance and client perception.

“You will build relationships with your clients by kind of walking through the thought process and letting them decide they’d rather spend more money and not have to treat her [again] versus just complain that you always pick the most expensive antibiotic when you get there,” Dorn explains.

Transparency strengthens trust and structured reasoning builds credibility.

9. How Does This Fit Antimicrobial Stewardship?

Every antimicrobial choice contributes to the broader stewardship landscape.

“Make sure that we protect those antibiotics that we want to be able to use,” Dorn says, praising the work AABP has done to ensure antimicrobial availability. “In order for all of us to be able to do this for generations to come, you have to think about this.”

Responsible antibiotic use in cattle requires:

Confirming bacterial disease
Targeting pathogens where they reside
Choosing appropriate, reachable drugs
Considering withdrawals
Evaluating practicality and cost
Preventing recurrence through management

Veterinary antimicrobial stewardship protects drug efficacy for future herds and future generations.

The Bottom Line

Antimicrobial selection in cattle is not about memorizing a gold standard drug. It is about systematically answering the practical questions.

“It’s not one gold standard,” Dorn says. “It is a continuum and it’s going to be tailored to the situation that’s in front of you. You need to take a look at the whole picture from the client and then come up with a best agreed-upon treatment plan.”

Taking a pause to consider the whole picture could be the most important step in making sound antimicrobial decisions.

The Role of Timing in BRD Retreatment Decisions

Thu, 12 Feb 2026 23:29:01 GMT

Retreatment decisions for bovine respiratory disease (BRD) are often made when animals fail to rebound as quickly as expected. A calf still looks depressed, a temperature remains elevated, or animal handlers question whether the initial therapy worked. In those moments, retreatment can feel like the safest option, but evidence suggests when cattle are eligible for retreatment can be just as important as what antimicrobials are used.

Post-treatment interval (PTI) refers to the amount of time that should pass after antimicrobial administration before an animal is eligible for another treatment. It’s not about delaying care arbitrarily, but about allowing drugs time to do what they are designed to do before concluding that further intervention is required.

“We have very high-quality medications and sometimes we need to let those drugs have enough time to work,” explains Dr. D.L. Step, senior professional services veterinarian at Boehringer Ingelheim. “By allowing that period of time, we don’t have to stress the animals by getting them up into a chute to be further evaluated for more treatment.”

PTI is a Clinical Decision

PTI is a question of timing. Once an animal meets a BRD case definition and receives antimicrobial therapy, clinicians must decide how long to wait before reassessing and potentially retreating. That decision is often influenced by clinical appearance and management pressure rather than pharmacologic behavior.

This raises the question: If retreatment happens too soon, are cattle actually failing therapy, or are they still in the expected window of recovery?

To examine that question, a 2020 field study evaluated PTIs following treatment with gamithromycin in cattle with naturally occurring BRD. Animals were assigned to retreatment eligibility at three, six, nine or 12 days.

The results revealed a clear pattern. Cattle eligible for retreatment at three days had higher retreatment rates. At the opposite extreme, cattle held to a 12-day PTI experienced poorer final outcomes, including higher case fatalities. The most favorable outcomes in this study occurred when retreatment eligibility fell between six and nine days.

These results suggest there is both a lower and an upper boundary for effective PTI, at least for gamithromycin.

These results are grounded in how gamithromycin behaves in the animal.

“Gamithromycin can stay in alveolar macrophages that fight infection down in the lung,” Step says. “We know the drug can stay there for up to 10 days.”

This persistence provides a biologic explanation for the observed outcomes. Retreatment at three days may occur before the drug has completed its therapeutic effect. Extending PTI too long, however, may delay intervention in animals that need further evaluation, which may explain the different outcomes at 12 days.

Handling stress may also be a contributing factor. Earlier retreatment requires pulling recovering cattle back through the chute, which may further compromise recovery.

When PTI did not change outcomes

Not all antimicrobials behave the same way. A more recent multisite study from Kansas State University evaluated PTIs following pradofloxacin treatment for BRD in stocker cattle. In that work, cattle were assigned to retreatment eligibility at three, six or nine days and followed for 45 days.

Within this range, no statistically significant differences were detected in the first treatment success, case fatality or days to death among PTI groups. Unlike the gamithromycin study, PTIs beyond nine days were not evaluated, so the effect of extended intervals could not be assessed.

The pradofloxacin findings reinforce an important point: PTI effects are drug-specific. These results do not mean that PTI timing is irrelevant, rather that no effect was detected under the conditions of this study.

PTI and Antimicrobial Stewardship

PTI is a stewardship issue grounded in outcomes, not restriction. In the gamithromycin study, shorter PTIs resulted in more antimicrobial use without improved performance. Allowing appropriate time between treatments reduced retreatment frequency and improved outcomes.

“If you wait a little bit longer, the outcomes are better and you don’t use as many drugs,” Step says.

This approach aligns stewardship with clinical effectiveness rather than limiting access to therapy.

What this Means for BRD Protocols

The practical takeaway is not a single retreatment day, but rather the opportunity for a retreatment window that reflects drug characteristics, cattle type and management conditions.

“A veterinarian can prescribe and say, ‘Maybe we wait seven or eight or nine days,’” Step says.

PTI should be considered alongside antimicrobial selection and case definition rigor.

By evaluating each case in context and adjusting protocols based on observed outcomes, PTI deserves the same level of attention as any other component of BRD treatment decision-making.

FDA Report Shows 16% Increase in Livestock Antimicrobial Sales in 2024

Thu, 08 Jan 2026 21:38:20 GMT

After years of relative stability, U.S. antimicrobial sales for food-producing animals rose in 2024. According to the FDA’s 2024 Summary Report on Antimicrobials Sold or Distributed for Use in Food-Producing Animals , sales of medically important antibiotics increased 16% compared with 2023, marking a notable reversal after nearly a decade of plateauing or declining volumes.

When it comes to cattle, this report raises an important question: Does this increase reflect a temporary response to disease and production pressures, or does it reflect a more durable change in antimicrobial purchasing patterns?

FDA Antimicrobial Sales Trends Show a Clear Rebound

FDA data shows antimicrobial sales for food-producing animals peaked in 2015, followed by sustained declines after growth-promotion indications were removed and veterinary oversight expanded. From 2016 through 2023, total sales largely stabilized or declined modestly, including a 2% decrease from 2022 to 2023.

(FDA)

This pattern changed in 2024. Total antimicrobial sales increased 16% year over year, representing the largest single-year increase since regulatory reforms took effect. While overall volumes remain approximately 27% below 2015 levels, the size and rebound stands out against nearly a decade of gradual reduction.

Which antimicrobial classes increased in 2024?

The 2024 increase was not evenly distributed across antimicrobial classes. Several medically important categories accounted for most of the growth:

Tetracyclines: ~20% increase; remains the largest class by volume
Aminoglycosides: ~37% increase
Lincosamides: ~11% increase

In contrast, penicillins declined by approximately 14%, despite remaining among the most commonly sold classes overall.

The concurrent rise across these classes likely reflects increased disease pressure and production challenges. While FDA sales data cannot identify clinical drivers, the pattern points toward greater reliance on core therapeutic drugs during a challenging production year.

Looking across species, 41% of medically important antimicrobial sales in 2024 were intended for cattle, 43% for swine, and 16% for poultry.

What the Data Show for Cattle

When looking specifically at cattle, tetracycline sales increased ~19%, aminoglycosides increased ~38%, sulfonamides increased ~24% and cephalosporins increased ~26%.

These antimicrobial classes are foundational tools in cattle medicine, particularly for respiratory and systemic disease. Tetracyclines are widely used across beef and dairy systems for bovine respiratory disease, anaplasmosis and reproductive tract infections, supported by broad-spectrum activity, multiple formulations and long-standing familiarity in practice. Aminoglycosides are used more selectively but are important for treating gram-negative and enteric infections, often in more severe cases. Lincosamides are commonly used for respiratory disease and certain anaerobic or foot infections.

To provide additional context, the FDA report also includes biomass-adjusted antimicrobial sales, including an interactive dashboard , which accounts for changes in animal population size and average live weight. This data could be a more meaningful indicator of antimicrobial use intensity.

Biomass-adjusted sales of aminoglycosides, amphenicols, cephalosporins, fluoroquinolones, lincosamides, sulfonamides and tetracyclines for cattle all increased from 2023 to 2024 representing a higher intensity of use.

Swine Data Also Showed Increases

The sale of medically important microbial drugs for use in swine increased 13% from 2023 to 2024. While annual sales for swine have been slowly increasing since 2020, this jump is much larger than it has been in previous years.

Looking at specific drug classes, Aminoglycoside sales increased ~25%, fluoroquinolones increased ~49%, sulfonamides increased ~15%, tetracyclines increased ~15%, and lincosamides increased ~13%.

In swine, aminoglycosides and sulfonamides are frequently used to manage enteric and respiratory conditions. Fluoroquinolones and tetracyclines are critical for addressing complex swine respiratory diseases and systemic infections, while lincosamides are often specifically targeted at combating swine dysentery, mycoplasmal pneumonia and infectious arthritis.

Biomass-adjusted sales of these drugs for swine all also increased from 2023 to 2024.

Sales Data are not the same as on-farm use

A critical point emphasized by FDA is sales and distribution data do not directly measure the actual use of antimicrobial drugs on farms. These drugs can be purchased in anticipation of use, be used at a later date or held in inventory for future needs. There is no national system in place that measures antimicrobial use across animal production sectors in real time. Year-to-year fluctuations in sales can reflect many factors including animal health needs, changes in livestock populations and evolving production practices.

Despite the rebound in 2024, food-animal antimicrobial sales remain significantly lower than a decade ago. Even so, the data reinforce the need for stewardship that balances effective disease control with antimicrobial resistance considerations, guided by clinical judgment and herd-level decision-making.

Veterinarians and Producers See BRD Risk Through Different Lenses

Wed, 31 Dec 2025 13:49:05 GMT

The hardest cattle health decisions often live in the gray zone. Nowhere is that truer than with bovine respiratory disease (BRD) in cattle that aren’t clearly high risk, but don’t look entirely safe either. A new survey suggests that when cattle fall into this medium-risk category, veterinarians and feedlot managers might be working from different mental playbooks.

The study, published in Translational Animal Science, examined how veterinarians and feedlot managers assess BRD risk and decide whether to use metaphylaxis when risk is uncertain. They surveyed 25 veterinarians consulting for a combined more than 600 feedlots and 30 feedlot managers. While both groups rely heavily on experience, the results show meaningful differences in how risk is perceived, what outcomes are expected and which factors ultimately tip the decision toward treatment.

Veterinarians and Producers Hold Different Expectations for BRD Outcomes

BRD remains one of the most costly and consequential diseases in feedlot cattle, driving losses through mortality, morbidity, treatment costs and long-term performance impacts. Metaphylaxis is widely accepted for cattle at high risk, but less straightforward when cattle fall somewhere in the middle.

In the survey, respondents were asked to consider hypothetical groups of medium-risk cattle and estimate expected morbidity and mortality if metaphylaxis were not used. Veterinarians consistently anticipated worse outcomes than feedlot managers. On average, vets expected higher percentages of sick cattle and greater death loss, while managers’ expectations were lower and more variable.

That difference matters. Expected disease burden strongly influences whether metaphylaxis is justified. If one party anticipates substantial losses and another expects manageable disease, alignment becomes difficult from the beginning.

Key Factors Used to Decide on Metaphylaxis

While both veterinarians and producers described metaphylaxis decisions as multifactorial, the survey revealed clear differences in which risk signals each group emphasizes most when cattle fall into the medium-risk category.

Veterinarians tended to emphasize factors tied to biological vulnerability and population-level disease risk, including:

Health history of the cattle, particularly prior illness, vaccination status and consistency of backgrounding
Degree of commingling, with mixed-source cattle viewed as substantially higher risk
Body weight and age, with lighter, younger cattle seen as less resilient
Transportation stress, including haul distance and time in transit
Weather conditions, especially temperature swings and adverse conditions at arrival
Expected morbidity and mortality, with vets more likely to anticipate higher disease impact if metaphylaxis was withheld

Veterinarians also placed strong weight on how these factors interact, rather than viewing any single signal in isolation. In the gray zone, multiple moderate risks stacking together often justified treatment.

Feedlot managers and producers, by contrast, placed greater emphasis on operational context and sourcing signals, including:

Cattle source and origin, particularly whether cattle came from known suppliers
Market channel, such as sale barn versus direct-from-ranch purchases
Historical performance of similar cattle, drawing heavily on prior closeouts
Visible condition at arrival, including fill, alertness and signs of stress
Variability within the load, with uneven cattle raising more concern than uniformly moderate-risk groups
Cost–benefit considerations, especially when expected disease levels were perceived as manageable

Producers were generally less likely than veterinarians to rate environmental conditions or body weight as primary decision drivers on their own, instead weighing how cattle had performed under similar circumstances in the past.

Where they aligned:

Before cattle arrived, both groups consistently identified market channel and cattle origin as the most influential pre-arrival indicators of risk. After arrival, overall cattle condition became the dominant real-time signal for both veterinarians and producers — often serving as the final checkpoint before deciding whether metaphylaxis was warranted.

Experience Continues to Guide Metaphylaxis Decisions

One of the study’s most striking findings is how heavily metaphylaxis decisions still depend on professional judgment rather than formalized thresholds. Respondents frequently described relying on gut feel, period outcomes with similar cattle and local norms.

That reliance on experience isn’t necessarily a flaw — BRD risk is complex and context-dependent — but it does introduce variability. Two operations receiving similar cattle under similar conditions might make different metaphylaxis decisions, with both believing they are acting responsibly.

From an antimicrobial stewardship standpoint, that variability is significant. Medium-risk cattle represent the largest opportunity and challenge for reducing unnecessary antibiotic use without increasing disease loss.

Opportunities to Better Align Veterinarians and Producers on BRD Risk

Rather than framing these differences as conflict, the authors point to an opportunity for better alignment. Veterinarians and managers bring complementary perspectives: Veterinarians tend to focus on population-level disease prevention, while managers weigh operation history, cost and day-to-day realities.

Clearer conversations around expected morbidity, acceptable loss thresholds and what success looks like for a given group of cattle could narrow the gap. So could shared post-placement reviews that compare expectations with actual outcomes, helping refine future decisions.

As scrutiny for antibiotic use in food animals continues to intensify, metaphylaxis decisions will only draw more attention. This study highlights that improving consistency doesn’t necessarily require new drugs or diagnostics, but better alignment between the people making the call.

When risk is uncertain, clarity between veterinarian and producer might be one of the most powerful tools available.