Jan. 1, 2017, marked a turning point for the U.S. livestock industry regarding the acquisition and handling of antibiotics. Amendments to the preceding Veterinary Feed Directive (VFD) now necessitate veterinarian oversight of many commonly used antibiotics that were previously available over-the-counter, and “production use” statements have been removed from product labels.
During the past 12 or more months, industry publications, websites and conferences from all facets of the livestock industry have thoroughly addressed the “hows” and “whats” of this new rule. For many producers, now is a good time to re-evaluate management protocols and to explore other technologies that may promote animal health and reduce the need for antibiotic use.
Why feed- and water-use drugs are affected
Feed and water use of antibiotics represent a large segment of drug use in livestock production systems, and many of those antibiotics were previously available over-the-counter. Therefore, the FDA chose to bring those drugs under veterinary oversight.
In 2014, the FDA reported that of the antibiotics used in animals considered “important to human medicine,” 74 percent were administered through feed and 21 percent through water (Figure 1).
Therefore, it is easy to see the VFD rule will touch a majority of antibiotics commonplace for livestock producers.
Participating members of industry and the FDA have recognized that maintaining the availability of antibiotics is essential to animal health in modern production systems. Furthermore, working to retain the efficacy of antibiotics available within the livestock industry through judicious use is imperative.
It is important to keep in mind that livestock producers have not lost the availability of these antibiotics, but the way they are to be acquired and used has changed.
The VFD rule includes antibiotics considered “medically important to humans” and are administered via feed. This rule has not impacted how all medications are obtained and handled. For example, ionophores (i.e., Rumensin, Bovatec) are not currently considered medically important and therefore do not require a VFD (unless used with a VFD drug).
Furthermore, over-the-counter antibiotics administered in injectable or bolus form are not impacted by this rule, and producers can still obtain them as before. Water-use antibiotics deemed “medically important” now require a prescription from your veterinarian.
Technology to promote animal health
As the livestock industry adjusts to this new regulatory environment and consumers continue to put emphasis on reducing and refining the use of antibiotics, producers may explore alternative technologies that promote animal health by maintaining the well-being of the gut and enhancing nutrient digestibility.
The gut of ruminants is an immunologically active organ which is constantly exposed to potentially toxic compounds through the ingestion of feed, the bedding and from the environment. Commensal bacteria occur naturally in the gut and provide a barrier against foreign organisms as their growth competitively restricts the growth of potential pathogens.
Additionally, these bacteria work to signal the animals’ immune system to produce immunologically important cells when necessary. Commensal bacteria also ferment carbohydrates and produce compounds that promote the growth and health of the absorptive cells in the gut.
With 70 percent of all immune cells located in the gut, it is the first line of defense against foreign pathogens.
Stress, pathogens, digestive upset and the use of antimicrobials can upset the balance of commensal bacteria, negatively impacting digestion and allowing opportunistic pathogens to invade and reproduce. Therefore, cultivating the health of the rumen and intestinal environment may serve to improve overall animal health and, therefore, performance.
The FDA defines direct-fed microbials (DFMs) as “products that are purported to contain live (viable) micro-organisms.” Direct-fed microbials include one or more of the following: probiotics, prebiotics, yeast, fungi and enzymes. Probiotics are live, beneficial organisms (often bacteria) which help improve and maintain the microbial balance of the intestinal environment.
Prebiotics are compounds (e.g., digestible fiber, yeast cultures) that provide a food source to promote the growth of probiotics and commensal bacteria. A synbiotic contains both a probiotic and prebiotic; this useful collaboration is more effective than the probiotic alone.
Research on direct-fed microbials
The impacts of feeding DFMs on the short-term health and performance of cattle under stress, such as receiving beef calves and young dairy calves, have been the focus of a growing body of research.
Disease-challenged and receiving beef calves supplemented with DFMs demonstrate reduced numbers of treatment pulls and increased dry matter intake, resulting in improved short-term bodyweight gain, when compared with calves receiving no DFMs.
Some studies exist where no performance or health benefit were realized from feeding a DFM. It is likely that the value of a DFM may be limited when used in situations absent of stress, physiological challenges or in particularly healthy cattle.
The 2011 National Animal Health Monitoring Service found that 35 percent of feedlots surveyed used a probiotic paste as part of an initial treatment for digestive disorders. Using a probiotic in combination with or following a treatment with an injectable antibiotic helps to repopulate the beneficial organisms in the gut that may be affected.
Bull calves from commercial dairies bound for use in the beef industry experience tremendous stress and health challenges which negatively impact calf performance, one of the most common being diarrhea and scours.
Administering beneficial organisms through the use of a DFM may encourage the intestinal environment of a calf experiencing diarrhea or scours to return to normal more quickly. The use of DFMs in dairy calves has been found to reduce the frequency of diarrhea and significantly reduce scouring extent.
The use of DFMs has also been associated with desirable changes of the digestive tract morphology of neonatal-transition dairy calves, such as greater ileal height and crypt depth prior to weaning and greater ruminal papillae width after weaning, all of which resulted in enhanced nutrient absorption and subsequently improved calf performance.
Pre-harvest intervention strategies to reduce the potential for foodborne illnesses, including E. coli O157:H7 and salmonella, have been a significant focus for packing plants.
It has been well accepted that supplementing feedlot cattle with a DFM at the end of the feeding period significantly reduces the shedding of E. coli O157:H7 by up to 50 percent – but has had limited impacts on reducing salmonella. Many natural-branded cattle feeding programs currently require the use of a DFM 30 days prior to slaughter as a method of pre-harvest pathogen intervention.
Considerations of use
DFMs contain one or more type of living organisms and therefore require consideration of the manner in which they are shipped, stored and administered to animals. These products are available in a variety of forms, such as granular, pastes, boluses, capsules, drenches and water-solubles.
If a water-soluble DFM is used in water or milk replacer, it is important to understand that chlorination, temperature, minerals, ionophores and antibiotics may impact the effectiveness of the product.
Additionally, if a granular DFM is being added to the feed along with a feed-grade antibiotic, the bacteria portion of the DFM product will likely be ineffective.
Finally, storage conditions such as extreme temperatures, direct sunlight, high humidity and presence of mineral premixes can impact the efficacy of DFM organisms. It is important to follow manufacturer recommendations when storing and administering these products.
There is no doubt that antibiotics have a place in modern livestock production to ensure animal health and food safety. The recent implementation of the Veterinary Feed Directive will change how livestock producers acquire many antibiotics that have been commonplace. These changes offer an opportunity to explore technologies like direct-fed microbials. 
Tony Grzemski, a regulatory coordinator with Agri-King, and Connor McDonald, an intern from North East High School in Goose Lake, Iowa, contributed to this article.
References omitted but are available upon request. Click here to email an editor.
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Aimee Hafla
- Beef Nutritionist
- Agri-King - Fulton, Illinois
- Email Aimee Hafla
