Dr Liesel van der Merwe is a small animal medicine
specialist. Send her your
questions:
This e-mail address is being protected from spambots. You need JavaScript enabled to view it
.
Dr Liesel van der Merwe
Last month we discussed adverse reactions to pet food. I classified health problems brought on by diet under four headings: Food intolerance, food allergies, toxins in the food and a nutritionally mediated disease.
In the case of nutritionally mediated disease there is nothing wrong with the food per se, but the food is not suited to certain individuals and will exacerbate or cause clinical disease in those pets.
Recent reports about an association between some pet foods, including some super premium brands, and heart disease was the impetus for this column.
Reports
In 2014, the Food and Drug Administration (FDA) first received a few reports of heart disease in dogs on specific grain-free diets and by April 2019, 524 reports of a condition called dilated cardiomyopathy (DCM) were registered. Of these, 515 were canine reports and nine feline reports.
The affected animals were eating the grain free products, which have higher levels of legumes and potato in them. The affected dogs developed DCM, which occurs when the heart muscle becomes thinner and flabbier, causing the heart to enlarge but also to contract very poorly, which leads to heart failure.
Breeds
DCM is a well-known condition in dogs and affects males preferentially and certain breeds in middle age: Giant breeds such as the Great Dane and Irish Wolfhound, Boerboel, Doberman and American Cocker spaniel.
Many cases of DCM that were reported to the FDA have included smaller atypical breeds of dogs as well as the more typically affected breeds, with the golden retriever featuring prominently.
It is important to note that the FDA believes there is a bias in that golden retrievers are probably overrepresented as they are a very popular breed and the breed society was very proactive in informing owners of the risk and association.
Recently a peer reviewed article reported on an increased number of cases noticed in golden retrievers; in some cases more than one dog being affected in a household, which is unusual.
Taurine
Once the history was analysed in these patients it became apparent that all of the animals were on a grain free, potato or legume enriched diet. This in turn seemed to cause a taurine deficiency in the dogs, which is an essential amino acid for the heart muscle. Taurine deficiency causes DCM.
Taurine deficient diets are well known as a cause for DCM in cats. Eventually all cat food had to be supplemented with taurine, and now the condition is quite rare in cats. Taurine-related DCM also occurs in spaniels.
Taurine is found in meat protein, which was part of the raw ingredients of the implicated dog foods. The total taurine was similar for both grain-free labelled and grain-containing products tested by the FDA.
Essential
Taurine is generally not considered an essential amino acid for dogs, because these animals can synthesize taurine from precursors, cysteine and methionine. Nearly all the grain-free products had taurine precursor levels above the minimum nutritional requirement for adult maintenance food for dogs.
So, at this stage there is no information as to why the taurine is low in affected animals, but levels did normalise in the affected dogs when they were placed on a normal diet, except for one dog, which was switched to another type of grain-free diet.
Phytates are found in high levels in legumes and are known to bind to proteins and some minerals, making them unavailable in the diet. However, this is a well-known phenomenon and methods to inactivate them include cooking, germination, fermentation and soaking.
Puzzling
A puzzling aspect of the recent spike in DCM cases is that they have occurred just in the last few years, whereas these dog food formulations have been on the market for much longer. The FDA is working with the pet food industry to try to understand whether changes in ingredients, ingredient sourcing, processing or formulation may have contributed to the development of DCM and to better understand if (and how) taurine metabolism (both absorption and excretion) may play a role in these reports of canine dilated cardiomyopathy.
So, in summary, adverse reaction to pet food is more complicated than just a missing ingredient or a toxic additive. Bear also in mind that millions of dogs are fed every year in the states and 500+ cases have been reported.
Even if we multiply the number by five to include possible unreported cases, we are still looking at a miniscule proportion of the total number of dogs fed, although it will always be terrible if your dog is one of those 500.
So, don’t panic. But, if you are concerned, get more information directly from affected companies. If you think that your pet may be affected, speak to your vet.
Sources:
|
