by George Looby, DVM
For decades there has been a strong difference of opinion among various vested groups regarding the merits of adding antibiotics to animal feeds for the purpose of increasing feed efficiency and minimizing the effects of possible low grade infections especially in young growing animals. Animal scientists and those engaged in food animal production have long held that the economic benefits of feed additives outweigh any possible adverse effects to the consumer. Many consumers on the other hand view the use of antimicrobials in animal feed as leading to increased microbial resistance to those important antibiotics used on a regular basis in human medicine, leading to greater resistance.
It was not long after the use of antibiotics become an integral part of treatment protocols in human medicine that animal scientists began to note that when antibiotics were added to the ration of certain animal groups, their rate of growth appeared to be significantly different then those without antibiotics. This difference was a positive one and it soon became common practice to mix low levels of antibiotics into the rations with rather strong evidence that feed efficiency was increased resulting in a shorter interval from weaning to market. The variety of antibiotics used as feed additives over the years has included many antibiotics recognized by the public and most, for a variety of reasons, are no longer widely used. The focus of American agriculture has long been to provide the consumer with the most economical, most nutritious, safest food products that it can provide. This has meant walking a tight rope balancing that which is technically possible against that which is acceptable to all concerned parties.
In recent years hospitals in particular have been increasingly plagued by the emergence of so-called “super bugs” which are resistant to many of the antibiotics most often used in treatment. The emergence of Methicillin Resistant Staphylococcus Aureus (MRSA) is likely to be one of the most important inciting forces behind the FDA imposing restrictions on antibiotic additives in animal feeds. Staphylococci are everwhere in nature, some good, some not but the very term is, for many, a cause for great alarm. Consumer groups have applied great pressure on the FDA to take such action as is necessary to eliminate antibiotics from animal feed.
The FDA is implementing a three-year plan during which manufacturers of pharmaceuticals would voluntarily revise their labels in such a way as to insure they no longer would be used as feed additives. Drug houses have three months in which to agree to this new format and agree to the terms of the proposal, after which the three year transition begins. After this period of transition the use of antibiotics in food producing will be allowed only under the direction of a licensed veterinarian where the health of an animal or group of animals is compromised by illness or the threat of illness. This would be equivalent to a prescription and designated a VFD or Veterinary Feed Directive which would be overseen by the FDA. Dosage schedule, animal group being treated and duration of treatment would be required on this form. This VFD rule is now open for public comment for a 90 day period which started on Dec. 12, 2013 and everyone is invited to comment at and insert Docket FDA-2010-N-0155.
As the system is now structured, many medically important medications can be sold over the counter. Medically important means that a particular drug has great importance in human medicine and takes precedence over its use as an animal feed additive. Under the terms of the new regulations, antibiotics can now be sold only with a prescription from a licensed veterinarian for the treatment of a target individual or group of animals for which the prescribed medication is considered the best and most effective treatment for the condition diagnosed.
The American Veterinary Medical Association (AV MA) has, for many years, supported and promoted the passage of such regulations. It is its position that with veterinary oversight the likelihood of inappropriate use of medically important antibiotics will be greatly reduced. The organization stands ready to assist the USDA and FDA in educating veterinarians, producers and feed suppliers as they transition to comply with the new guidelines over the next three years. It is likely that with this feed additive no longer available, producers are going to be forced to look more carefully at their overall production protocols and sharpen their management skills. Old practices that have been somewhat displaced will once more surface to insure that production goals now commonplace are not lost.
How certain bacteria develop a resistance to a given antibiotic is somewhat complex but there are a few points that perhaps will make the process somewhat more understandable. A given bug does not develop resistance to a particular drug to counteract that drug but rather resistance arises as the result of genetic mutations within a gene sequence. It is by chance that a particular mutation produces changes within that cell that allows for drug resistance. This change gives the organism containing the mutated cells an advantage over those cells that do not carry the mutated gene sequence. When antibiotics are added to a host (animal/human) whether ill or not (ex. feed lot cattle), the bacteria whose genetic profile has been changed and is now resistant to that drug giving it the opportunity to quickly outgrow those bacteria who succumb to its action. This process sets up something of a snowball effect whereby these altered bugs rapidly take over the host within which they find themselves.
When a group of animals on low levels of antibiotics are sent to market in good condition but whose bacterial population has been altered, these same bacteria find their way into the human food chain. The first weak link may very well be on the packing house floor where the rapid flow of animals on the processing line may compromise the best levels of sanitation.
Once in the shopping cart of the consumer the manner in which it is handled from that point forward will depend greatly of the knowledge of the consumer. Proper handling in the kitchen will do much to counteract any possible adverse effects of the product purchased.
We have reached an important milestone in addressing the issue of antibiotic resistance. It was not arrived at easily but everyone involved can be assured that the beneficial end result will far outweigh any negative issues that may surface as an aftermath.