October 14, 2016
Answers: What Dry Food Does to Your Cat's Gut
Last Updated on Saturday, August 13, 2016 08:51 PM
Published on Saturday, August 13, 2016 07:48 PM
Written by Guillermo Díaz, MV
作者：獸醫基勒摩．迪亞茲（Guillermo Diaz, MV）
I want to switch my cat over to a raw meat diet, but, in the meantime I'm still feeding her dry food. I notice she throws it up pretty often, almost always soon after eating it. What is it about dry food that makes cats throw it up? The barf looks almost the same as when it went in!
"Why did my cat throw up?" is one of the most common questions vets get asked. Vomit is the first defense mechanism by which cats protect themselves from the absorption of substances that could harm them. For the purposes of this article, I'm going to consider "vomit" everything a cat expels from her mouth, regardless if it's digested or not. Cats have a relatively short gastrointestinal or GI tract, powerful abdominal muscles and a very delicate and precise sympathetic nervous system that can detect potential harmful substances and allow the cat to expel them.
Cats have evolved as strict carnivores. They are highly specialized to ingest, digest and absorb animal protein and fat efficiently. Cats have developed scissor-like teeth designed exclusively to rip, tear and chew meat and bones. When fed dry kibble, their teeth are not efficient at coping with all those tiny pellets by chewing. As a consequence, most of the kibble is swallowed intact.
Because of the extreme low water content of dry commercial diets, usually between 5 and 10 percent on average, once those pellets are swallowed they tend to absorb great amounts of water from saliva and gastric juices, so they can be digested. But, in the process and as a collateral effect, these pellets get swollen and many times exceed the capacity of the stomach, stretching its wall and the nerve fibers within. This sends SOS signals to the medulla oblongata in the brain, the center for the vomit response, generating the process we all have witnessed at least once: our cat begins to meow in a weird manner and to retch, which is an acute vomiting episode, throwing up the food she ate a few minutes ago. That is the origin of those weird tubular structures made of wet kibble we find on the floor. The message the cat's GI tract is sending is: "I cannot digest this food." This is one of the effects, a mechanical effect, of dry kibble on your cat's gut.
Vomit in cats is not a normal event, and it is a red flag that something is going wrong. Many pathologies include vomiting as a symptom; that is why you need to take your cat to the vet for a checkup and rule out disease as a possible cause. Here are some of the problems that can make cats throw up:
- Food intolerance
- Food allergy
- Gastritis, acute and chronic
- Liver diseases
- Drugs and chemicals
- Renal insufficiency
Another effect of dry kibble is on the immune system. Many cats do develop allergies to dry foods; this is the reason for intermittent vomiting over a long period of time. If the cat is fine, looks healthy, maintains a normal weight, doesn't look ill and has normal energy levels, but just throws up occasionally, you should consider a food allergy as the possible cause. In both cases, mechanical and immune, there's damage done to the integrity of the gut wall.
Let's have a quick glance at the microscopic view of the gut. From the outer layer to the inner layer:
- Serosa: This is the "cover" sheet of the gut and lies all along the GI tract.
- Muscular layer: Smooth muscle fibers running along and across the intestines and stomach. This layer allows the GI tract to move and contract itself, called peristalsis, facilitating digestion.
- Submucosa: The location where the digestive glands are located as well as the blood supply.
- Mucosa: The inner layer where the molecular digestion occurs. It has finger-like structures or "villi" covered by the enterocytes.
Due to mechanical and/or immune damage to the mucosa, a disruption, or rupture, occurs in this delicate barrier, allowing the passage of undigested nutrients, i.e. proteins, many types of additives and preservatives from the food and bacteria from the gut and from the food into the bloodstream. All of these are now allergens. These whole, undigested molecules are detected by the immune system generating an immune response and sensitizing the individual to that, or those, specific antigens present in the food.¹
The intestinal mucosa is a very efficient barrier that limits the absorption of macromolecules. After the antigen is exposed or presented for the first time to the mucosa generally, a local immune response develops. This inflammatory response reduces the amount of antigenic material absorbed and if the noxious stimulus persists the response will be general, as in all over the body. When the inflammation of the GI tract is established and the patient has remained untreated, the absorption rate increases because of the vasodilation of the mucosa, thus allowing the intake of greater amounts of allergens, causing a vicious cycle. When this happens, the first clinical sign generally observed is vomiting, sometimes with blood present. The signs that follow can be diarrhea/loose stools, anorexia, itchiness, alopecia, uneasiness, excessive licking, hair loss and secondary skin infections.² ³
If the short intestine is involved, the diarrhea is characterized by a large volume of loose, watery stools, poor body condition and weight loss. In many cases of cats with chronic inflammation of the GI tract, diarrhea is not present until a stressful event occurs, such as pregnancy, parturition or a change of environment.⁴
The best and most effective way to stop this vicious cycle is to stop feeding the cat the species-inappropriate food and provide the patient with the raw natural choices available. Do not forget, the GI tract has a great capacity to renew its lining cells at an extraordinary rate, even outpacing all other tissues. Let's give Mother Nature a chance to heal.
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Dr. Guillermo Díaz studied veterinary medicine at the Universidad Mayor de San Marcos in Lima, Perú. He currently practices in Lima and also provides veterinary services to a large number of local rescue organizations.
本文作者獸醫基勒摩．迪亞茲(Dr. Guillermo Diza) 就讀位於秘魯利馬的 Universidad Mayor de San Marcos 獸醫系。他目前在利馬執業，同時提供許多當地的動物救援組織獸醫服務。
1. TR Tams, "Chronic Feline Inflammatory Bowel Disorders," Compendium on Continuing Education for the Practicing Veterinarian 8, no. 6, 1986, 371-376.
2. JR August, Consultations in Feline Internal Medicine, 5th ed., Elsevier, Nov 2006.
3. E Baker, "Food Allergy in a Cat," Feline Practice 5, 1975, 18-26.
4. DN Carlotti, "Food Allergy in Dogs and Cats, A Review Report of 43 Cases," Veterinary Dermatology 1, June 1990, 55-62.