Below is a summary of the issues for both vegan cats and dogs, for your reference.

For both ethical and health reasons, many vegetarians and vegans choose to feed their companion dogs and cats vegetarian or vegan diets. Up to 50 % of commercial pet food brands are comprised of “meat meal” and “byproducts,” which include various body parts (such as beaks, brain, spinal cord tissue, bones, lungs, intestinal tracts) slaughterhouse wastes, 4-D meat (from dead, dying, diseased or disabled animals), supermarket rejects, as well as rendered dogs and cats from animal shelters.  Other contaminants which have been found in commercial dog and cat foods include old restaurant grease complete with high concentrations of dangerous free radicals and trans fatty acids; PCBs, heavy metals and other toxins, particularly from fish; bacterial, protozoal, fungal, viral, and prion contaminants, along with their associated endotoxins and mycotoxins; hormone and antibiotic residues; and dangerous preservatives. Many speculate that the dramatic increase in incidences of cancers, kidney failure, and many other degenerative diseases in our companion animals in recent years may be due to the harmful ingredients in many commercial meat-based pet foods.  This has led people to feed alternative diets.

Although cats are biologically carnivores, in many cases they can be successfully maintained on a vegan diet as long as it meets all of the nutritional requirements specific to cats and their overall health is adequately monitored, with particular attention to urinary tract health especially in male cats. Cats require the same nine essential amino acids that are needed in the diet of all mammals. However, in addition, cats also require arginine and taurine. Taurine is found naturally in meat but can be supplied in synthetic form. (In fact, most of the commercially available meat-based cat foods are supplemented with synthetic taurine.)  Without adequate taurine, cats will suffer retinal damage and go blind and may also develop dilated cardiomyopathy (a type of heart disease).  Other essential nutrients that cats require include arachidonic acid and vitamins  A and D, which can also be supplied to formulate a balanced, nutritionally complete vegan diet for cats.

One problem which can afflict cats on a nutritionally balanced and complete vegan diet is FLUTD (feline lower urinary tract disease), which is a syndrome that is more likely to occur if urinary struvite crystals or stones form secondary to urinary alkalinization and a diet too high in magnesium.  Due to anatomical differences, male cats are much more likely to get FLUTD and urinary obstruction, but female cats can (rarely) be affected as well. Ensuring adequate water intake is important for preventing excessive urine crystals, and eventually stones as well.  This can be accomplished by feeding a canned diet, adding water to dry food, or adding a pinch of salt to food to stimulate thirst. Cats on a vegan diet can develop abnormally alkaline (high pH) urine due to the more alkaline pH of plant based proteins in comparison to the acidic pH of meat-based foods which cats have evolved to eat.  When the urine pH becomes too alkaline, there is an increased risk of formation of struvite (also known as magnesium ammonium phosphate) bladder crystals and/or stones.  Calcium oxalate stones can also occur, but these do not occur if the urine is too alkaline, but rather if it is too acidic.  Such stones can create irritation and infection of the urinary tract and require veterinary treatment.  In male cats who form such crystals or stones, they can suffer more severe consequences than simply irritation or infection of the urinary tract because the stones can actually cause an obstruction of the urethra so the cat cannot urinate.  This is a life-threatening emergency requiring immediate veterinary care; this involves passing a urinary catheter to relieve the obstruction, placing an indwelling urinary catheter, and starting supportive intravenous fluid therapy, along with appropriate pain management and antibiotics if indicated.  These “blocked” cats frequently need to be hospitalized and monitored closely for several days before they can go home and the associated veterinary fees can easily be between $1000-$1200.  Depending on the duration and severity, urinary blockage can be fatal due to accumulation of toxins in the bloodstream and/or complications associated with urinary bladder rupture, tears in the urethra, and damage to the lining of the bladder and urethra from stones, crystals, and even the catheterization itself.  The sooner a problem is identified and the cat is treated, the better the prognosis for recovery.  As a practicing veterinarian, I have had several cats with life-threatening urinary blockage come in to see me.  (None of these cats were on a vegan diet, to my knowledge.)  To emphasize the severity of this condition, I will add that one of these cats was euthanized due to re-blockage after catheterization and lack of caretaker finances to pursue treatment further (especially in light of the worsening prognosis, as cats who block once are at a high risk for blocking again), and another cat had to be referred to a specialist for surgical repair of a urethral tear.  Some cats who get blocked repeatedly require a highly specialized (and expensive, ~$2000) surgery called a perineal urethrostomy (PU).

Therefore, cat guardians who decide to put their cat on a vegan diet should bring their cat to their veterinarian to have the urine pH tested 1-2 weeks after switching them to a vegan diet and then once a month for the first several months to ensure the pH remains stable.  If the pH is too high, there are urinary acidifiers which may help the urine pH to be more acidic.  Urinary acidifiers that may be used include methionine, vitamin C, and sodium bisulfate.  James Peden, author of “Vegetarian Cats and Dogs” states there are also natural urinary acidifiers, including asparagus, peas, brown rice, oats, lentils, garbanzos, corn, Brussels sprouts, lamb’s quarters (the herb Chenopodium album, also known as pigweed), most nuts (except almonds and coconut), grains (not millet), and wheat gluten (used in kibble recipes).  Once the pH is regulated (with or without the use of appropriate urinary acidifiers, the urine pH should be checked at least twice a year.  If a cat shows signs of pain or straining while using the litter box, immediate veterinary attention should be sought.  It is important to not supplement the cat’s diet with urinary acidifiers unless it is actually needed because a too acidic pH can cause a different kind of stone to form (calcium oxalate stones). While many cats appear to thrive on a vegan diet, there are also many anecdotal reports of cats having recurring urinary tract problems, including urinary tract infections associated with previous urethral obstructions caused by crystal formation.

For cat guardians who find it too tedious to monitor their cat’s urine pH, they should perhaps consider feeding a non-vegetarian cat food or not keeping a cat as a companion.  Another option is a special pH-adjusted vegan formula available through Harbingers of a New Age (http://www.vegepet.com/) which requires the caretaker to make home-baked kibble using the supplement mix and the vegan recipe provided by HOANA.

Most of the available veterinary prescription diets (such as those manufactured by Hill’s and Purina) which are designed to aid in treatment of a variety of illnesses, including diabetes, kidney failure, liver disease, inflammatory bowel disease, and urinary stones do contain animal products.   Hill’s c/d is a prescription diet low in dietary magnesium formulated to prevent recurrence of struvite urinary stones by maintaining a normal acid urine pH (between 6.2-6.4).

Also, many cats are very picky eaters.  Although adding vegan mock meats and nutritional yeast to flavor vegan cat food will encourage many cats to eat it, there may be many cats who still refuse to eat, especially if they are sick.  Cats who are anorectic for a prolonged period are at high risk for developing hepatic lipidosis, or fatty liver syndrome, which is a serious condition requiring extended hospitalized care.  Some cats may require more patience and a gradual transition from a meat-based diet to a vegan diet if they have been accustomed to eating a meat-based diet.  Most commercial pet foods contain “digest” which consists of partially digested chicken entrails, that makes the food more palatable.

On the positive side, many cat and dog guardians have reported improved overall health, vitality, coat quality, and fewer problems with skin allergies, food allergies, and various degenerative diseases.