Eggs From Backyard Chickens - Protect your health and avoid drug residues
Published on Sat, 02/04/2017 - 8:00am
Chicken eggs are one of the healthiest foods on the planet. They are high in protein, low in calories, and have zero sugar, carbs, or glutens. In fact, a steady supply of healthy eggs is probably one of the main reasons why people keep backyard chickens. But, there’s a downside when chicken-keepers don’t follow manufacturer recommendations for medications used to keep their flock healthy—drug residues. These residues in chickens and in other foods we eat, like beef and pork, have been addressed by the USDA and its Food Animal Residue And Depletion (FARAD) program.
As human consumption of eggs from backyard chickens rises, it becomes more important for veterinarians to be able to advise their clients on safe practices. Central to these concerns is eating eggs from medicated birds and for consumers to be aware of things to consider when treating their birds with over-the-counter medications.
Backyard chickens have essentially become companion animals rather than just food sources. Poultry veterinarians use drugs to treat chickens to combat disease, overcome or prevent parasitic infections, or alleviate pain and suffering in an injured bird. There are also some over-the-counter medications available that owners might consider using to treat their birds.
Modern veterinary drugs are highly effective and can be life-saving. They can also prevent unnecessary pain and suffering in animals. It is important, however, that these medications are used appropriately so that their benefits are maximized while potentially adverse effects—in both humans and animals—are kept to a minimum.
In addition to direct drug exposure, indirect drug exposure can occur when free-ranging chickens inadvertently consume materials that contain drug products—a common occurrence might be chickens eating manure from a horse recently treated with oral medications. Thus, humans eating eggs produced by chickens in non-commercial settings should be aware of potential contaminants.
It is important to remember that humans can be exposed to drug residues by eating eggs from hens that were treated with medications. Depending on the drug, eggs might need to be discarded for a period of time after the last day of treatment because drugs are absorbed and can distribute to various parts of the body, including reproductive organs where the eggs are formed.
Adverse effects from exposure to drug residues in food may be immediate and quite severe, such as an allergic reaction to antibiotics like penicillin. But the concern is more often the long-term effect of prolonged exposure. In all food-producing animals treated with medications, sufficient time must be allowed for the animal to excrete the drug from its body so that concentrations in the tissues and eggs can drop to concentrations that are at or below levels that are safe for consumption. This is called the “withdrawal interval.”
Waiting on withdrawal
These safe concentrations are determined in scientific studies designed to determine how much of a specific drug a human can be exposed to over the duration of his or her lifetime without any adverse effects. Lifetime exposure is a worst-case scenario, but it’s important to follow a conservative approach for any risks to human health.
All veterinary drugs approved for use in food-producing animals by the Food and Drug Administration, or FDA, have a withdrawal time on the label to inform users of the length of time they must allow between administering the last dose and eating any products from the treated animal.These are based on human health studies, and studies of how fast the drug is excreted from treated animals.
Veterinarians treating backyard poultry are faced with twin challenges: There are very few drug products on the market that meet the medical needs of these hens and are practical to use.
For example, the dosing instructions may not be suitable for smaller flocks kept in free-range systems. Part of this challenge is due to the fact that most FDA-approved medications for laying hens are designed to meet the needs of large scale operations. In this setting, mass treatment of a large numbers of birds—sometimes in the thousands—is the rule. Additionally, a zero-withdrawal time for eggs due to the production aspects of a layer facility are a prime consideration.
Commercial production problems
A good example of medications commonly used for treating chickens are “dewormers.” There are very few “dewormers” labeled for use in all classes of chickens—that is, for broilers, non-laying hens, and egg-laying hens. The ones that are available contain hygromycin B and are formulated as medicated feeds or premixes. These formulations are practical for commercial production where the amount and source of food that the birds receive can be tightly regulated.
In contrast, a backyard or free range setting usually means small numbers of birds with access to several different sources of food. In this backyard setting, these formulations are very difficult to use and ensure that the birds actually consume the product, let alone receive the correct dosage.
Consequently, avian veterinarians treating back yard chickens or owners with companion birds often seek alternative products to treat parasites. Unfortunately, the only other products that are approved for chickens are not labeled for hens laying eggs—these products, like Wazine, contain piperazine and dipiperazine. These have a withdrawal time for meat, but it cannot be determined from the label how long the eggs should be withheld to ensure the safety of people eating them. The legal term for using a drug in a way that is not specifically stated on the FDA-approved label is referred to as “extra-label.”
An important factor to keep in mind is that chickens producing eggs for human consumption are considered food animals, regardless of whether they are in a back yard or in a commercial setting. A further restriction for food-producing animals is that drugs may only be used extra-label for the treatment and prevention of imminent disease and not for management purposes or to enhance production. If there is any deviation from the label instructions for over-the-counter medications, such as those purchased in a feed store, then a veterinarian must prescribe that medication’s use.
A valid veterinarian-client relationship requires that the veterinarian has consulted with the client—the owner of the animals—and has examined the animals or has sufficient information to make a diagnosis and a treatment recommendation. The veterinarian then prescribes a drug for the treatment of the diagnosed condition.
Breaking the food chain
The veterinarian takes full responsibility for the safety and efficacy of that treatment and so has to provide the client with detailed instructions as to how the drug must be administered. These instructions should include a recommendation for a withdrawal interval when animals produce products for human consumption. Again, this withdrawal interval is the time after treatment stops so that the animal meat or by-products—such as eggs— will not enter the human food chain.
For extra-label drug use, a veterinarian must base their withdrawal interval recommendation on scientific data. If the FDA has not approved the drug for laying hens, this data is typically unavailable from the pharmaceutical company. In these cases, veterinarians look for data in the public domain, including papers published in peer-reviewed scientific journals and summaries of data submitted for drug approval in other countries. Most veterinarians do not have such data at their fingertips, but they can contact the Food Animal Residue Avoidance Databank, or FARAD for help.
FARAD is a national program that assists veterinarians, livestock producers, and state and federal regulatory and extension specialists to avoid drug residue violations and pesticide contamination of animal-derived food products like milk, honey, and eggs. This service protects public health and helps minimize antibiotic resistance. Practicing veterinarians can get free advice from FARAD through the internet or by phone calls.
When there is uncertainty about the proper withdrawal interval after using drugs in an extra-label manner. or if animals are accidentally exposed to environmental toxins, pesticides, or biotoxins, FARAD can help. This service is especially useful for situations where there are very few approved products available, like treating backyard chicken flocks.
About the authors
Lisa Tell, DVM, Dipl. ABVP (Avian) and ACZM, is the Western Region Director for the Food Animal Residue Avoidance and Depletion program. She is a professor with the UC Davis School of Veterinary Medicine, and has more than 20 years of clinical expertise with birds. Dr. Tell recently authored a book chapter highlighting drug residue avoidance in backyard poultry.
Ronette Gehring, BVSc, MMedVet (Pharm), Dipl. ACVCP, is the Midwest Region Director for the Food Animal Residue Avoidance and Depletion program. She is an Associate Professor with the College of Veterinary Medicine at Kansas State University, where she studies drug movement and residues in food-producing animals. Dr. Gehring has authored and co-authored many publications about drug residue avoidance in both the scientific and lay press.