Innovative dog chews and treats are all the rage these days. Despite the claims of their sellers, most of these products are new twists on an old theme – taking the parts of food animals that we typically discard as inedible waste and turning them into expensive and often highly sought after dog treats. A few examples are bully sticks, pig ears, pig/cow hooves, cod skins, and the topic of this essay, beef gullets (esophagus) and tracheae. In addition to coming in a dried form as a chew, the entire neck regions of beef, lamb, chicken, turkey and other food animals are also included in some commercial and homemade raw diets.
The Question Is: Are gullets and tracheae (necks) safe for dogs to consume?
The Answer: Not if the thyroid gland came along for the ride.
Quick Anatomy Lesson: The thyroid gland is a small organ that wraps around the upper portion of an animal’s trachea (wind pipe). When a cow is dissected for the production of human-grade meat, the trachea and esophagus are removed together as by-products. Although a law passed in 1986 prohibits their inclusion in human foods, these animal parts can be used in pet foods, which is exactly where they end up (along with other animal by-products that are deemed not for human consumption).
Thyroid Tissue in Your Dog’s Food: Thyroid tissue contains the hormone thyroxine, which will not be destroyed by the dog’s gastric acid or digestive enzymes. It is absorbed into the body and remains active. If a dog consumes enough thyroxine from the diet, an elevation in circulating thyroid hormone occurs and the dog develops hyperthyroidism (or more technically correct, thyroidtoxicosis). Some dogs develop elevated serum thyroxine but do not show clinical signs. Others develop signs that include weight loss, hyperactivity, excessive panting, and polydipsia/polyuria (increased drinking/urinating).
So, is this a problem that owners should be concerned with? Possibly; especially if you are feeding a raw diet. Here is the evidence:
- Twelve dogs fed raw diets: In 2012, German veterinarians at Justus Liebig University reported elevated plasma thyroxine levels in dogs that were being fed either a raw diet or large amounts of fresh or dried beef gullet (1). Clinical signs of hyperthyroidism were reported in half of the dogs (6/12). Following diagnosis, seven owners immediately switched to a commercial dry food and stopped feeding gullet. Veterinary rechecks 2 weeks and 2 months later revealed that plasma thyroxine concentrations had returned to normal in all dogs and clinical signs had resolved. One owner did not change her dog’s diet. Repeated thyroid hormone tests showed elevated levels one and four months following diagnosis and the dog was experiencing chronic weight loss. At that point, the owner switched the dog to another food, clinical signs resolved and plasma thyroxine levels returned to normal.
- Two more cases: Two cases were reported in 2014. In the first, an 11-month-old male Rottweiler was examined for signs of weight loss, excessive panting and increased blood thyroxine levels (2). A complete diet history revealed that the dog was being fed a commercial raw diet. After switching the dog to a commercial dry food, signs resolved and blood thyroxine levels returned to normal. In a second case study, a two-year-old female Miniature Pinscher was examined for a failure to come into estrus (3). The dog was fed a homemade raw diet that included beef cuts from the head and neck region purchased from a local butcher shop. The dog had highly elevated serum thyroxine levels. Changing the dog’s diet led to normalization of serum thyroxine and normal estrus cycles.
- Raw foods and chews: Most recently, a study published in the Journal of the American Veterinary Medical Association reported findings of thyrotoxicosis in 14 dogs fed either a commercial raw diet or a variety of different chews or treats (4). All of the treats were some type of sliced or rolled jerky chew. Clinical signs resolved and thyroid hormone levels were normalized within four weeks of discontinuing the suspect products. The authors were able to obtain seven samples of the brands of food or treats that owners were feeding. When tested, all had elevated thyroxine levels when compared with control foods. The authors end with this statement: “The presence of high T4 concentrations in a variety of pet foods or treats sold under different labels suggests that the problem of thyroid tissue contamination of such items may be widespread and not confined to only a few products or manufacturers.” (The authors also sent samples and identifying information about the products to the FDA for further investigation).
Take Away for Dog Folks: Okay, before raw feeders start flooding my blog with hate mail and sending in the trolls, let me state up front that these research results are by no means presented as a personal vendetta against feeding raw.
NO TROLLS PLEASE
Those of you who have read Dog Food Logic know that my position is that there are many approaches to feeding dogs healthfully, and a well-balanced, properly selected (and sourced) raw diet can be one of those approaches.
However, the evidence strongly suggests that the recent increase in diet-induced hyperthyroidism is likely a result of the increased popularity of both raw diets and of feeding unusual types of chews such as gullets and tracheae to dogs. At the very least, this set of case studies provides sufficient evidence that diet-induced hyperthyroidism is a health risk that warrants further study and investigation of the identified companies and brands.
UP ON MY SOAPBOX
Draggin’ out the ol’ box: Fear not. I do have a personal opinion on this matter (though I would be hesitant to go so far [yet] as to call it a vendetta). This has to do with data reported in the 2015 study, which were collected in the United States. In that study, all 14 of the dogs were being fed commercially prepared foods at the time of diagnosis. These were foods that the owners purchased from a company, trusting that the products would not only provide good nutrition to their dogs, but that they were SAFE. This should not be such a high bar to clear, yet it repeatedly seems to be for the pet food industry.
Here’s the thing: The knowledge that the presence of animal thyroid tissue in foods can cause hyperthyroidism is not new information. Outbreaks of diet-induced hyperthyroidism in people are well-documented and are the reason that “gullet trimming” as a source of ground beef was outlawed in the 1980’s. Yet, these tissues are still allowed in the foods that we feed to our companion animals. Why is this?
I maintain that pet owners should be able to easily discover exactly what is in the pet foods they feed to their dogs, including the source and quality of the product’s protein ingredients. Yet this information is rarely provided and requests are often ignored, denied or responded to with evasive platitudes and assurances. Here’s a suggestion – Ask your pet food manufacturer if the food that you feed contains animal necks and if they guarantee that it does not contain thyroid tissue. Let me know what you hear back.
In a perfect world (and when I am queen), we will ban the inclusion of unsafe body parts in the foods that we feed to our canine family members. I know it is an outrageous suggestion, but a person can dream, cant’ she?
Got Gullet? Let’s hope not.
Cited References:
- Kohler B, Stengel C, Neiger R. Dietary hyperthyroidism in dogs. Journal of Small Animal Practice 2012; 523:182-184.
- Cornelissen S, De Roover K, Paepe D, Hesta M, Van der Meulen E, Daminet S. Dietary hyperthyroidism in a Rottweiler. Vlaams Diergeneeskundig Tijdschrift 2014; 83:306-311.
- Sontas BH, Schwendenwein I, Schafer-Somi S. Primary anestrus due to dietary hyperthyroidism in a Miniature Pinscher bitch. Canadian Veterinary Journal 2014; 55:781-785.
- Broome MR, Peterson ME, Kemppainen RJ, Parker VJ, Richter KP. Exogenous thyrotoxicosis in dogs attributable to consumption of all-meat commercial dog food or treats containing excessive thyroid hormone: 14 cases (2008-2013). Journal of the American Animal Hospital Association 2015; 246:105-111.
The Science Dog 
That’s one I hadn’t thought of, but makes good sense, and thank you. Although it’s often hard to get good information on prepared foods, most treats are even worse. So at this point I’ve moved to a dehydrator so I know what’s going in them.
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Hi Gerry – Agree that it is impossible to learn what we need to know about treats. Even something as simple as source of ingredients or where they are produced is often not readily revealed to owners. I bet your dogs love the dehydrated treats!
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Very good, one can slice chicken breast in thin slices and put dehydrator or oven until they are cooped like a treat.
Also sweet potatoes can be cut in slices and make treats than you know what your dog is getting.
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I meant cooked like a treat. After you cut them into slices.
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I emailed one treat manufacturer that advertised as Made in the USA to ask where the the ingreadients were sourced and they were very cagey about it. They wouldn’t answer in the email and wanted me to call them. I never bought the treats again, I figured if they didn’t want to be open about it then I’ll buy elswhere. These days I mostly get treats from Honest Kitchen or other companies that advertise where they source the ingredients.
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So strange that they wanted you to call – perhaps because they did not want a record of their response in writing? Definitely agree that cagey is not a positive company behavior and warrants looking for treats elsewhere!
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I’m not able to find a free readable source for any of the papers – at least yet. Did they describe the exact diet the dogs were fed? Was the mix of meats constantly high in thyroid content?
I would *think* but I don’t know having not read the papers that a diet that sometimes contains thyroid should be OK. But if the research says differently – please share! I make dog diets and sometimes if I can get some fresh parts, I feed them – at this point only to my own dogs, though I’ve gotten client inquiries. It’s only occasionally, but if I’m potentially harming my dogs I certainly want to know!
There are actually supplement companies out there, Standard Process comes to mind off the top of my head, who sell high thyroid extract content supplements (http://www.standardprocess.com/Products/Veterinary-Formulas/Canine-Thyroid-Support#.VjLiGjHF-So) for the treatment of thyroid disease. Could this supplement potentially be dangerous?
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Hi “Run a Muck” – You can obtain full source by emailing the corresponding authors and asking for the paper. The 2015 paper did identify most of the foods and chews that were fed. Certainly a raw diet that contains all parts of an animal would contain a small amount of thyroxine. The problem appears to be one of quantity and the use of beef necks both in the production of chews and as a primary protein source in a raw diet (either homemade or commercial). At highest risk are dogs who are fed diets comprised primarily of beef necks (and possibly chicken necks), and as the final study shows, companies who are producing raw foods using a large proportion of necks (which is hidden from the consumer – there is no way to know if this is the case other than contacting the company and asking).
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Thank you! My initial searches were of the full citations. When I searched again just for authors, I was able to access the full papers!
I think the findings are yet another cautionary tale of understanding just exactly what one is feeding to a dog – and yet another reason to avoid the ground meats of local co-op provided BARF mixes. At least here locally, when I asked whether or not the source meats were inspected, I was told they didn’t have to be. To me, and I could be wrong, and given the significantly lower price of the co-op ground meats when compared to grocery ground meats, the consumer is still getting a hodge podge of waste, ground so as to be completely unidentifiable, and the only difference between it and what goes into commercial dog foods is that it isn’t processed into meal form. I’m not surprised that health issues can result from overdoses of this waste material.
When making home made, use only whole roasts, whole birds and whole fish as the base. Know the nutrients and know their effects!
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Very interesting, thanks. My immediate thought was; what about African wild dogs, which eat every edible bit of a carcase ? – one of the dogs in a pack is getting a whole thyroid gland.
OK, it turns out that I am nearly 120 years behind the curve – Kohler et al cite a study from 1898 which showed that fresh thryroid is not toxic, but that frozen thyroid is. Puzzle resolved.
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Hi Peter – Yes, of course. The difference is in quantity. The problem as it appears at this point in time (i.e. without any controlled research trials – these were all case studies) appears to be one of over-feeding animal by-products, in this case, beef necks, that contain thyroid tissue. These dogs were not consuming entire carcasses – they were being fed a diet comprised of a large proportion of beef necks (and I would speculate that feeding dogs a diet comprised primarily of another by-product, chicken necks, would also be at increased risk. But, again, we would need to study this to find out). Last – Not sure about the veracity of the study that you cite comparing frozen with fresh thyroid tissue – from 1898? I did not read anything of that nature, so cannot comment.
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Would feeding chicken carcasses mean my dogs are getting thyroid glands??? Or is it only beef that is an issue? (This may explain my dogs behaviour!)
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Janelle – Entire carcasses would most likely be of low risk. If you were feeding primarily chicken necks, I would be concerned and would advise to feed a higher quality protein source or at the very least to provide a variety of animal protein sources. If you are worried, checking a dog’s thyroid hormone levels is a simple blood test that your veterinarian can do for you.
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Thanks for again disseminating information on something no else is even talking about! Sharing this everywhere.
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Hi Eileen – Thanks – This information shocked me too, and there is not much out there anymore that can do that! 🙂
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Thank you for the wonderful post.
I feed my dog “Instinct” raw diet. I emailed the manufacture asking if they used trachea in their raw products and the response I got back was, “We do not use by products.” I suppose trachea is considered to be a by-product. Not as clear of an email response as I was hoping.
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Hi Cassandra, Yes, tracheas are definitely a meat by-product, so the answer that you received is technically correct. Still, I agree that it seems evasive – why not just say “No, we do not use tracheas in our products”. It might be worth another email saying, “Yes, but does that specifically mean that you do not use the neck tissue (esophagus and trachea) of any of the food animals in your foods?” My guess is that they are being forthright and did mean to answer you more clearly, but it would be nice to nail it down a bit more specifically, I agree. So glad that you did this – and am happy (generally) with the response that you received! Linda Case
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As usual, your articles are we’ll backed up with case literature and common sense.
It is inspiration and pleasure to read them.
Thank you!
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Thank you Milka! I am glad that you enjoy The Science Dog and find the articles helpful! Linda
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Thank you for this great article. I immediately emailed the two companies that we mainly use for our dog kibble, which is Wellness and Taste of the Wild. Wellness already responded and confirmed that they only use muscle meat in their recipes and have asked me to forward them this article. Wellness also has great treats, etc. so it seems like it might be a safe one to go with.
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Hi Valeska – This is very good news (and many thanks to Wellness for being so prompt and forthright – great to hear!) I agree that this would provide much confidence in their products. Best wishes, Linda
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Do you know if heat deactivates the hormone? I usually bake chews before giving to sanitize. I am NOT a raw feeder.
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Hi Micha – It appears that the cooking temperatures used to cook meat (ground beef) for human consumption does not destroy (inactivate) thyroxine, since people who consumed gullet-trimmed meat in the 1980’s developed thyroidtoxicosis. However, I have not been able to find (and am still searching) information about whether or not the high temperatures used in the production of protein meals and during extrusion will destroy active hormone. My inclination is to think that that degree of heat treatment would render thyroxine inactive and that this is why we do not see a problem with extruded products (plus the quantity issue, of course). If you are baking neck meat before feeding, I would probably still advise caution – mainly to limit how many “necks” you use as treats, if that is the type of meat that you are using. Will post again if I find anything about the temperature needed to deactivate. Thanks for the note and for reading. Linda
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I am working at slaughterhouses and I see which parts of the karkassen normally go to pet food industry: hart, long, liver and the nek area. The rest is for human consumption or Goes to destruction. So to think raw food for pets is made of meat as we eat it is an illusion, even the hygiene standards for those products are lower than for human meat products. And if nek is included in the pet food, it can be a substantial volume. But I think it is important to use as much of an animal if it has to be slaughtered anyway, as long as it is safe for our pets (in my humble opinion, heat it up before you eat it…)
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I emailed Taste of the Wild and they replied with this- I asked our Veterinarian, Dr. Heldman, and she said that while we use organ meat from human consumption slaughterhouses we do not use the gullet (throat tissue that may contain the thyroid) as that has already been discarded by the slaughterhouse since it is not safe for people either.
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Hi Kelly – It is so great to receive a detailed and complete response! Kudos to Dr. Heldman and to Taste of the Wild! Very good news and encouraging to see this type of transparency and clear answer! Thanks for asking them and for posting the response that you received! Linda
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I e-mailed Primal which is part of what I feed my dog and cats and they responded that they do not include any of the trachea or thyroid tissue. That everything in their product is fit for human consumption.
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Hi Betsy – This is great to know – both that they do not include trachea in their products and that they are formulating to meet human grade regulations. Thanks for posting! Linda
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I emailed My Pet Carnivore, where I get my raw food. This is their response (in less than 24 hours!).
Suzy,
Thank you so much for the inquiry! We’re so glad your girls are happy! So, the thyroid is NOT removed from any of the whole-ground foods, but it’s such a minuscule presence in the whole animal that it’s not likely to be a cause for concern.
Where the thyroid IS a concern is any of the things that include ground trachea and gullet. Though the thyroid is removed from any of the neck-only products, there can still be some hormone leaching from the thyroid before removal, so some dogs may still have an issue. The goat and lamb trim are also a potential concern, because much of the meat in those bulk boxes is from the neck. Hopefully that helps! If there’s anything else we can do for you, please don’t hesitate to ask!
All the best,
The My Pet Carnivore Team
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