MSU Extension Pork

Antimicrobial resistance (AMR) occurs when bacteria, viruses, fungi, or parasites develop resistance to the drugs used to treat or prevent infections. This is a major public health concern, as it can make infections in humans and animals more difficult to treat, leading to increased morbidity, mortality, and healthcare costs. Antimicrobials are fed to livestock to prevent disease and overuse and misuse can lead to the development of AMR in both animals and humans. To address this issue, the Food and Drug Administration (FDA) has taken several steps to reduce the use of antimicrobials in livestock.

The FDA issued guidance which recommended that animal drug sponsors voluntarily remove indications for growth promotion and feed efficiency from the approved uses of medically important antimicrobials. In 2015 the FDA issued the Veterinary Feed Directive (VFD) rule under the oversight of the United States Department of Agriculture. The VFD was implemented in 2017 to regulate the use of medically important antimicrobial drugs in food-producing animals, including swine. The VFD requires that all such drugs be used under the supervision of a licensed veterinarian and only for the specific purposes of preventing or treating disease, and not for growth promotion.

The U.S. meat and dairy industries are committed to ensuring that livestock farmers use medically important antimicrobials responsibly. Based on sales and distribution data, there has been a significant decrease in purchases of medically important antimicrobial drugs used in food producing animals, including swine. In 2021, in the swine sector alone, sales and distribution of these drugs decreased by 25% since the VFD implementation.

Continued monitoring and regulation of antimicrobial use in animal agriculture remains essential. Five years post VFD implementation, Michigan State University Extension (MSUE) wondered how these guidelines have affected Michigan pork producer and swine veterinarian perceptions regarding impacts on antimicrobial use, herd health, and other farm management practices aimed at controlling disease.

A survey for Michigan pork producers and veterinarians was distributed to explore how herd health and management practices have changed since VFD implementation. The survey, conducted by MSU Extension educators and specialists, was funded by a grant from Michigan Animal Agriculture Alliance.  It was administered in 2022 using both on-line and in-person formats. The survey asked questions about perceived antimicrobial use patterns and how they may have changed on farms as of January 2017. Questions included whether use of feed-grade antimicrobials had increased, stayed the same, or decreased; whether there were changes in the use of vaccines; and if health prevention measures such as farm biosecurity measures had been altered. The survey asked the producers if they thought the incidence or severity of common swine diseases has changed during the past 5 years. Surveys completed by swine veterinarians asked similar questions, but also included questions regarding how knowledgeable their clients were about VFD.  If interested, copies of the surveys can be accessed or completed using the following links:

Veterinary survey 

Producer survey

Swine producer survey results

Surveys were completed by 25 pork producers. The survey was completed by large-scale commercial pork producers, farmers raising pigs for direct sales and freezer meat, or for 4-H projects and pets.

Since the VFD implementation, approximately half of the producers surveyed continue using antimicrobials given in feed or in water. Seventy-two percent reported their overall antibiotic use has not changed since VFD was implemented (Table 1). 24% of producers reported a decrease in use of feed-grade antimicrobials since implementation of VFD; 20% reported increased use of injected antimicrobials while 68% claimed no change in use of injectable products (Table 1).

Importantly, many producers responding to this survey stated the overall health status of their herd has not changed since implementation of VFD (Table 1). Looking more closely at specific health conditions producers are noticing: 56% observed coughing, and 40% observed diarrhea or scours and labored breathing as big concerns on their farm. Conditions less frequently noted included: fever, lameness, skin issues, reproductive problems, and poor body condition which, when combined, account for 44% of major concerns reported.

Since VFD implementation in 2017, most producers (76%) stated they have not changed their normal vaccination routine (Table 1). The most frequently used vaccines by swine producers responding to the survey target influenza, porcine circovirus (PCV2), mycoplasma hyopneumoniae, leptospirosis, erysphillus, and parvovirus. Other vaccines used less frequently included: E. coli, porcine respiratory reproductive syndrome virus (PRRSv), and clostridium.

Regarding reproductive health, 64% of the producers that maintained breeding/farrowing operations have observed no changes in reproductive health issues. Of those reporting changes in reproductive herd health status, mummies or stillborn, feet issues or lameness, and dystocia were noted. Most (72%) farmers housing boars on their farm reported no changes in overall boar health since 2017.

The survey asked producers to report which non-antimicrobial approaches they are using to manage disease, including biosecurity measures and other farm management processes. The use of carbadox, pre- or probiotics, zinc oxide and other minerals, organic acids, herbs, ractopamine, virginiamycin, bacitracin, and other ionophores were reported.  Producers also reported greater reliance on increased biosecurity and other farm management procedures to help maintain herd health. Some examples described by farmers responding to the survey included: cleaning and disinfecting equipment and surfaces, use of individualized pig care, greater emphasis on use of vaccines and dewormers on a more routine basis, attention to the herd environment, proper nutrition, and clean water, quarantining and isolating sick and new pigs, and checking herd health history (Table 1).

Swine veterinarian survey results

The survey was completed by 15 swine veterinarians practicing in 11 Michigan counties, plus 4 that practice in multiple states (Table 2). Their practices included service to large ( more than 5,000 head) production systems, mid-sized (less than 1000 head), and small (less than 100 head) farms, breeders, farms raising a few head for freezer meat or direct sales, and individuals raising pigs as pets.  Among veterinarians completing the survey, 81% reported having discussed VFD implementation with their clients and 56% of the veterinarians currently prescribe VFD-required antibiotics for farms they serve (Table 2).

Most veterinarians completing this survey reported that their clients have reduced use of feed-grade antimicrobials (Table 2).  In-feed medication is prescribed most frequently to treat respiratory diseases and diarrhea or scours.  Among veterinarians surveyed, VFDs for feed-grade antimicrobials were requested for about half of the farms they serve (Table 2).  Consistent with these findings, 69% of the swine veterinarians reported that their prescriptions for injectable antimicrobials have increased since 2017.

As per vaccine usage, 44% of the swine veterinarians reported increased use of vaccine products to prevent herd diseases among their swine clients.  The most frequently prescribed vaccines included those for prevention of losses due to disease causing lower reproductive health such as parvo virus and respiratory diseases such as Mycoplasma hyopneumoniae and porcine circovirus type 2 (PCV2) (Table 2).

Despite, or perhaps due to, the increase in vaccination for reproductive health in boars or sows, 88% of swine veterinarians with oversight of breeding stock reported no changes in either boar herd health or reproductive health of herds in general.

In terms of farm management practices aimed at disease prevention or control, swine veterinarians are recommending disinfection, strategic use of vaccines and deworming agents, proper nutrition and clean water, and strict adherence to other farm biosecurity measures (rodent control, quarantining new animals, use of sick pens) and proper manure management practices (Table 2).

*Veterinarian responses about practices of clients they work with.

Outreach efforts in response to the survey

The MSU Extension pork team has produced a series of articles and fact sheets to raise awareness of, and evidence-based solutions for, many of the issues raised by Michigan pork producers and swine veterinarians through this survey. They have created a resources section on the MSU Extension pork team site titled Management over Medication, which includes a set of complementary short videos describing practical applications of approaches described by these articles and fact sheets.