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What’s in season? How swine veterinarians are managing seasonal spikes in bacterial disease in the new VFD era

Seasonal changes traditionally bring fickle weather, dramatic swings in day-night temperatures and, of course, flare-ups of respiratory and enteric disease in swine herds.

For pork producers, that used to mean adding an antibiotic to the grower-finisher rations or, at the very least, pulse feeding a medication at 7-day intervals to keep the seasonal bugs at bay.

But that’s all changed. Producers can still get old standbys like chlortetracycline, lincomycin and sulfamethazine, but now they’re more than a phone call away. Under the new veterinary feed directive (VFD) rules that took effect last year, most feed-grade antibiotic orders need to go through a veterinarian. And even then, there needs to be a veterinarian-client-patient relationship, or VCPR, which means the veterinarian needs to be familiar with the herd and make routine visits to the site.

In short: No VCPR, no VFD.

The pork industry has done a great job adapting to the new rules, according to Chris Rademacher, DVM, swine veterinarian at Iowa State University Extension. He thinks feed medications will continue to be valuable tools for managing bacterial respiratory and enteric diseases.

At the same time, he thinks producers will learn to place more emphasis on monitoring individual pigs and being more selective with antibiotic treatments.

More targeted approach

“We need to return to placing more emphasis on identifying sick pigs earlier and treating them with injectable antibiotics, rather than always relying on mass medication via the feed or water to treat all the animals,” he told Pig Health Today.

The veterinarian pointed to recent research at Iowa State University (ISU) that demonstrated the wide swings in feed and water consumption that occur with diseased pigs — a variable that doesn’t exist when using injectable medications.

How will the pork industry proactively protect herds from bacterial disease while playing by the new rules? That, in essence, was the question Rademacher and his colleague, Lee Schultz, PhD, put to 50 practicing swine veterinarians with more than 20 years’ experience.1 The survey was conducted just prior to the new VFD guidelines. Their responses, which follow, provide a snapshot of how the swine-health landscape is changing.


If producers have relied on antibiotics to clean up the opportunistic secondary bacterial infections that contribute to devastating porcine respiratory disease complex — particularly Mycoplasma hyopneumoniae, Pasteurella multocida, Haemophilus parasuis, Streptococcus suis, Actinobacillus suis— then improving vaccinations targeting the primary viral agents should help. Those vaccines commonly include porcine reproductive and respiratory syndrome (PRRS) virus, influenza A virus, porcine circovirus type 2 and porcine epidemic diarrhea (PED) virus.

The new VFD rules gave producers and their veterinarians a good opportunity to review all vaccination and treatment protocols, says Lisa Becton, DVM, director of swine health information and research, National Pork Board.

“Rapid detection can help manage sick pigs more effectively and prevent virus spread,” she says, urging veterinarians and farm managers to discuss seasonal changes and corresponding action plans. “It’s also a good idea to run through some of the symptoms that could surface among pigs to assist with daily animal observations and a quick response.”


Keeping viral diseases such as PRRS and PED in check will also make herds less susceptible to bacterial infections requiring antibiotics.

“These [viral] diseases are more widespread in cooler, wetter conditions, so it’s important to strictly enforce biosecurity measures,” Becton says.

That seasonal increase in disease pressure means veterinarians will probably urge producers to perform more biosecurity audits than normal, Rademacher says, looking for holes in the system that can be corrected relatively quickly and cheaply — those that may have been seen as not quite cost-effective in the days when over-the-counter antibiotics were readily available.

Two potential candidates: Power-washing marketing trailers when they return to the site and being more diligent about resisting temptation to mix back in a few tail-ender pigs from the end of one flow to the beginning of another.

ISU’s online Production Animal Disease Risk Assessment Program, or PADRAP, offers a set of risk-assessment questionnaires, databases and reports to help benchmark your disease risk and give a good biosecurity review. It has been proven to accurately predict how long a herd can expect to go without a PRRS break based on its biosecurity level.


Finishing pens can be stocked at a higher density in cool, changeable weather as long as feed and water are sufficient. In the past, producers might have been more comfortable with this approach if there was an antibiotic in the feed. That’s still an option, of course, and not all feed medications require a VFD. Still, reviewing stocking density and other environmental factors is a prerequisite for proactive disease management.

Mike Brumm, PhD, former University of Nebraska swine specialist and now facilities consultant, suggests the average stocking density for US finishing facilities is about 7.2 square feet per pig, but it ranges between 6.8 to 8.0. Because those densities have animals on the very edge of performance, producers may want to rethink that space allowance in the face of the VFD and loosen them up a bit, according to the survey.


The reduced access to some antibiotics has ramped up the availability of non-antibiotic additives, as well as the marketing claims that often go with them. Several classes of alternatives have been tried — probiotics, prebiotics, organic acids, enzymes, phytogenics, metals, hyper-immune egg yolk immune bodies, antimicrobial peptides, bacteriophages and even clay.

Many of those have demonstrated some benefit in livestock and poultry. However, questions remain about how they work, what the mechanism is for many, how to better standardize their effects, and how to improve their effectiveness in the real world, USDA molecular biologist Hyun Lillehoj, PhD, reported last year in the scientific journal Animal Health Research Reviews.2


Because in-feed antibiotics were traditionally seen as health insurance policies, limited access to medically important ones could make some producers less willing to commingle multi-source pigs or buy pigs that don’t come from health-assured sources, Rademacher says.


Although researchers have known for decades the physiological effect cooler temperatures can have on pigs, particularly baby pigs, they’re only now coming to fully appreciate the impact it makes on the pig’s immune system.

One study in 2012, for instance, showed baby pigs at 64° F were unable to mount a fever response necessary to fight infection and also showed a more damaging immune response compared to pigs housed at 93° F.3

That insight helps explain why a simple draft in the barn can prove so damaging. It also makes a properly functioning ventilation system the top priority in fall.

“Walk through your operation and see what needs fine-tuning, whether that involves building maintenance, manure-management strategies, staff scheduling or vaccination protocols,” Becton says.


Producers are accustomed to making ration changes in anticipation of pigs’ tendency to eat more feed in cool weather to compensate for heat production. Now, some additional feed adjustments may be prudent because the medically important antibiotics can’t be used for improving growth rate or feed conversion. Most cost-effective diet changes probably will be made in the nursery and creep feeds, where better ingredients and more labor-intensive feed management can make a difference in feed consumption in the all-important first few days on feed.


Rademacher and the study’s co-author Schulz presented a short list of additional practices that will help ensure responsible antibiotic management — most notably, training employees to spot diseases better, increasing veterinary involvement, increasing weaning age and managing the operation to better stabilize sow-herd health, pig flow and disease elimination.

And finally, don’t forget that access to antibiotics is the same in 2018 as it was before the new rules took effect, Rademacher says. Other than removing performance claims from antibiotics deemed medically important by FDA, none of the currently available products’ therapeutic claims have changed significantly under the new VFD rules.

In the end, Rademacher insists, all the VFD did was insert better relationships between veterinarians and producers where they might have been weak or nonexistent before. Considering the ever-present threat of seasonal health challenges, that’s not necessarily a bad thing.




1. Schulz LL, Rademacher CJ. Food and Drug Administration Guidance 209 and 213 and Veterinary Feed Directive regulations regarding antibiotic use in livestock: A survey of preparation and anticipated impacts in the swine industry. J Swine Health Production. 2017 Sept/Oct:25(5):247-255.
2. Gadde U, Kim WH, Oh ST, Lillehoj HS. Alternatives to antibiotics for maximizing growth performance and feed efficiency in poultry: a review. Anim Health Res Rev. 2017 Jun;18(1):26-45.
3. Carroll JA, Burdick NC, Chase CC Jr, Coleman SW, Spiers DE. Influence of environmental temperature on the physiological, endocrine, and immune responses in livestock exposed to a provocative immune challenge. Domest Anim Endocrinol. 2012 Aug;43(2):146-53.


Posted on August 5, 2018

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