MSU Extension Pork

Minimizing animal and human health risks associated with antibiotic resistance is central to policies implemented during the past few years by U.S. pork producers. Specific recommendations for managing antibiotic use are included in the current certification program adopted by commercial pork producers (PQA PLUS) and reinforced by National Pork Producers Council in its Pork Industry Guide to Responsible Antibiotic Use. To help ensure responsible antibiotic use, these guidelines stress the importance of pork producers working closely with veterinarians to develop disease prevention strategies best matched to their farm, sound record keeping/transparency, use of alternatives to antibiotics when possible, and other measures designed to ensure sustainability of U.S. pork production.

Annual Summary Report for 2018 for antimicrobials sold for use in food producing animals

In the case of antibiotics used for veterinary purposes, the Food and Drug Administration (FDA) tracks each product’s sales and distribution records to estimate amount of each class of antibiotic used in animals. Manufacturers and distributors are required to report by Dec. 31 each year, accurate data on their company’s sales from the previous year (i.e., the FDA Summary Report issued on Dec. 10, 2019 covers antibiotics sold during all of 2018). By law, results reported for each drug class include intended animal species, route of administration (i.e., in-feed, in-water, topical, injectable), and whether the product was meant for U.S. or export use. For historical context, past results are also included in the FDA Summary Report for these indicators every year these data have been collected by FDA, beginning in 2009. The rationale for using sales/distribution data instead of direct use data is based on: a) accurate data for sales and distribution are readily available from records maintained by antibiotic manufacturers, while accurate use data are very difficult to track, and b) historical data suggest that most antibiotic purchased for animals is actually used by farmers to prevent or treat the conditions it is approved for. 

The FDA Summary Report for 2018 shows that, when data are combined for all medically important antibiotic sales for all species of livestock, the amount (reported as total weight, not number of doses) increased by 9% over 2017; this translates to a net increase of 492,739 kg of drug (Table 1). Looking at data for sales and distribution of medically important antibiotics for use in pigs only, the year-over-year increase was about 17% (increased by 351,416 kg).

Closer look at 2018 antibiotic sales data for pigs 

Most of the increase in sales of medically important antibiotics used for pork production in 2018 came from sale of tetracyclines, especially chlortetracycline and oxytetracycline. This is not surprising, given that tetracyclines have accounted for about 80% of the total U.S. market for feed grade antibiotics used in pigs during the past several years (Table 2). These compounds possess a broad spectrum of activity that includes Gram+ and Gram- bacteria, and are frequently used to treat scours caused by E.coli and respiratory diseases including atrophic rhinitis, pneumonic pasteurellosis and Mycoplasma infections. They are also easy to administer in safe doses and relatively inexpensive (e.g., less than 20 cents/dose for a 30-pound pig).

Sales of aminoglycoside and sulfa-containing antibiotics for use in swine also increased by greater than 40% in 2018, while lincosamides declined by 19%. However, their net impact on total antibiotic sales for swine was small because amounts of these three classes combined was less than 6% that of the tetracyclines (Table 2). 

In the FDA Summary Report, sales of medically important antibiotics sold as injectables (e.g., includes some macrolides, aminoglycosides, cephalosporins, quinolones) are not broken down by species, but combined for all species. Sales (number of kg sold) in 2018 declined by about 1% from 2017. The combined amount of injectable antibiotics sold for use in livestock in 2018 was about 6% that of the combined sales of products administered orally; that pattern has been consistent since 2009 when tracking of these data began.

Sales of non-medically important antimicrobials, which includes ionophores and a few very small sales volume products not used in human medicine, saw U.S. sales for use in pigs of 414,170 kg in 2018; an increase of 5% over 2017 levels. Ionophores are sold mainly for use in fed cattle and poultry, which together accounted for 86% of their total sales in 2018.

Possible reasons for the 2018 uptick in antibiotic sales for use in swine production 

At this point, we are not aware of published reports describing possible reasons why medically important antibiotic sales for use in U.S. agriculture increased during 2018. However, possible explanations include increased U.S. herd size, increased average slaughter weight, increased incidence of disease, less labor or less experienced labor, and other market dynamics; each of these may have contributed a portion of the gains.

Slaughter hog number, average weight of hogs at slaughter, and weight of pork produced are key endpoints tracked carefully by the USDA, and each of these indicators increased between 2017 and 2018.  Looking at commercial packer dressed weights, for example, pork production increased by 3% (from 25,437 to 26,177 million pounds). It is reasonable to believe that this increase in production probably accounted for part of the increase in sales of medically important antibiotics.

Another possible explanation for why sales and delivery of certain classes of medically important antibiotics increased is that these antibiotics were purchased in order to prevent or treat disease conditions that may have seen small increases in 2017 and 2018. Indeed, based on a 2018 national survey initiated by MSU Extension Veterinary Feed Directive Year 1 in Review, 31% of swine producers who responded reported an increase in swine sickness following implementation of Veterinary Feed Directive (VFD) guidelines, and 18% said they would like to learn more about non-antibiotic options for sick animals (follow-up action most frequently requested in the survey). In this survey, similar results were reported for cattle, which also showed an increase in antibiotic sales in 2018. 

A third possible explanation for the increased sales of tetracyclines in 2018 may be related to farm labor shortages which have been widely reported. Antibiotic delivered in-feed or water requires less labor than that required for individual animal administration by injection.

It’s also possible that part of the sales increase reported for 2018, relative to 2017, was a simple reflection of market dynamics whereby suppliers, veterinarians and producers purchased larger amounts of certain drugs in late 2016 anticipating possible impacts of VFD implementation on veterinary pharmaceutical distribution chains. Also, producers who had an excellent year in 2018 may have accelerated purchases late in the year, anticipating future use in 2019.

Non-antibiotic options for disease prevention and control 

Most pork producers advocate further reduction in use of medically important antibiotics when effective alternative measures to prevent disease are available. Other options for ensuring herd health, which include improved husbandry and biosecurity measures and disease surveillance, increased use of vaccines, and use of selected probiotics and other nutritionals (when solid supporting evidence exists). It may also be useful to consider non-medically important antibiotics (e.g., ionophores, such as narasin) and use of individual animal (usually injectable) antibiotics, when necessary. Advice on how to implement these and other measures to help reduce reliance on feed grade antibiotics in swine production has been the subject of several recent publications (see for example Impact Assessment). Because pig health issues can vary markedly year-by-year and are often regional or even farm specific, your veterinarian or nutritionist are the best sources of ideas for strategies to reduce the use of medically important antibiotics for your herd. 

U.S. pork producers remain committed to responsible use of antibiotics 

While it is useful to pay attention to year-over-year antibiotic sales data, it is also important to recognize that results from one year don’t necessarily indicate a new trend; numerous factors influence when and how antibiotics are used to combat disease in pigs and other livestock. In spite of the uptick, FDA data suggest overall use in 2018 of medically important antibiotics in pigs and other livestock was still the second lowest, for the year, since 2009 when this metric for antibiotic sales to livestock producers was first reported. Importantly, 97% of medically important antibiotic sales for use in pigs in 2018 came with a veterinarian’s prescription and/or under a VFD. These findings demonstrate that, in spite of the modest increase reported in 2018, overall use of antibiotics for swine production, when normalized against pounds of pork produced, remains well below historical averages, and suggest U.S. pork producers remain committed and on the right track in their antibiotic stewardship efforts.

Table 1. Summary for all medically important antibiotics sold for use in U.S. livestock production, by species, for the period 2016-2018.

*Amounts reported in kg of active drug ingredient. Amounts include antibiotics given orally and by injection. However, injected drugs only accounted for about 6% of total sold and amounts were steady over this 3-year reporting period, averaging about 354,000 kg/year.

Table 2. Summary of top five medically important antibiotics sold for use in U.S. swine production (only) for the period 2016-2018 

^*2016 – Last year before VFD guidelines fully implemented. 

For additional web-based information about pork production, visit Michigan State University Extension, Pork Working Group or contact: Dave Thompson, thom1637@msu.edu 269-832-8403, Casey Zangaro, zangaroc@msu.edu 785-285-2127 or Beth Ferry, franzeli@msu.edu, 269-927-5674.