As we have been working through the implementation of the new Veterinary Feed Directive (VFD) rules, there is lot we have learned. The implementation of these new rules has not turned out as badly as we expected, but most certainly, many questions have come up. We were fortunate to have had previous experience with VFDs. Even so, because we all want to follow the rules, many questions have arisen on how to address some specific situations. The initial response is that the VFD rules need to have very clear and specific answers to all our questions. Although this might seem like a good option, we must be very careful of what we ask for.

The challenge becomes that, as we ask for clarification on a specific issue, we force commitment to the specific answer. Although it may seem like a good answer at the time, it is likely to constrain our options on future situations that may vary slightly. The more specific rules become, the more black and white they may appear, but the more they may limit our practice of veterinary medicine. We may think of this as comparable to any diagnostic assay. All assays have a diagnostic sensitivity and specificity. Diagnostic sensitivity is defined as the ability to correctly identify all positive samples from a group of known positives (high diagnostic sensitivity = small number of false negatives). Diagnostic specificity is defined as the ability to correctly identify all negative samples from a group of known negatives (high specificity = small number of false positives). Generally, the more we improve the diagnostic sensitivity of an assay, the more likely it is to have false positives (lower specificity). The opposite is also true: as an assay’s diagnostic specificity improves, the more likely it is to have false negatives (lower sensitivity).

So in the case of the new VFD regulations, the more specific the rule becomes (ie, the more it clarifies each specific situation) the more likely it is that slight deviations of the scenario will be considered illegal, even though we would all agree that clinically, these scenarios are exactly the same. This situation is comparable to a polymerase chain reaction (PCR) test, in that the more nucleotides we add to the primer, the more specific it becomes, and the more likely that we will miss a slight variation of the pathogen (lower sensitivity). As field veterinarians, we look at a multitude of different pieces of clinical information (history, signalment, clinical signs, diagnostic results, etc) to make decisions. Sometimes we rely on culture of the organism, a PCR, or histologic changes to confirm the etiologic diagnosis. Sometimes our diagnosis is made in one group of pigs, and on the basis of epidemiological testing and pathogenesis, it applies to other pigs in the same flow. That is the science and practice of veterinary medicine. That is something we want to keep at our discretion rather than allow any regulatory agency to dictate to us.

Yes, many things in life are not black and white. In school, many times we have to make things simple to make them seem black and white so they can be graded. So, although ambiguity creates uncertainty (some areas of gray), we must be careful of what we ask for. There is no doubt we will be seeing more and more regulation of our clinical decision-making, especially regarding antimicrobial use. We are all behind judicious use of antimicrobials. We must continue to be proactive in ensuring these new regulations do not affect our ability to treat pigs in a timely manner, so we can protect our pigs’ health and welfare and prevent and relieve pig suffering, while still maintaining the utmost in safe food and protecting public health. All of these are critical parts of our veterinary oath.

Alex Ramirez, DVM
AASV President