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.
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.
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.
- 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.
Excerpted from: “Only Have Eyes for Your: Exploring Canine Research with the Science Dog” (2016).