Appendix I: study

Wakefield LA et al. Evaluation of cats fed vegetarian diets and attitudes of their caregivers. J Amer Vet Med Assoc 2006; 229(1): 70-73.
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Objective—To determine motivation and feeding practices of people who feed their cats vegetarian diets as well as taurine and cobalamin status of cats consuming vegetarian diets.
Design—Cross-sectional study.
Animals—34 cats that had been exclusively fed a commercial or homemade vegetarian diet and 52 cats that had been fed a conventional diet for ≥ 1 year.
Procedures—Participants were recruited through a Web site and from attendees of a national animal welfare conference. Caregivers of cats in both groups answered a telephone questionnaire regarding feeding practices for their cats. Blood was obtained from a subset of cats that had been fed vegetarian diets. Blood and plasma taurine and serum cobalamin concentrations were measured.
Results—People who fed vegetarian diets to their cats did so largely for ethical considerations and were more likely than people who fed conventional diets to believe that there are health benefits associated with a vegetarian diet and that conventional commercial cat foods are unwholesome. Both groups were aware of the potential health problems that could arise from improperly formulated vegetarian diets. All cats evaluated had serum cobalamin concentrations within reference range, and 14 of 17 had blood taurine concentrations within reference range.
Conclusions and Clinical Relevance—Vegetarian diets are fed to cats primarily for ethical considerations. Results of this study should aid practitioners in communicating with and providing advice to such clients.

Appendix II: nutritionally inadequate diets

After extensively searching the biomedical literature, I can confirm that at least one study does exist demonstrating a disease of malnutrition, namely hypokalaemic polymyopathy, in cats fed a vegetarian diet. However, the diet was known prior to the commencement of the study to have been nutritionally inadequate. The study abstract is provided below.

I have been unable to locate any other studies demonstrating diseases of malnutrition in cats or dogs maintained on vegetarian diets. Despite the popular belief that vegetarian diets are inevitably harmful for companion animals, there were no studies demonstrating this using nutritionally complete and balanced vegetarian diets.

Leon A, Bain SA, Levick WR. Hypokalaemic episodic polymyopathy in cats fed a vegetarian diet. Aust Vet J. 1992 Oct;69(10):249-54.

A previously undocumented hypokalaemic condition with a cyclical nature, comprising acute bouts of polymyopathy followed by spontaneous recoveries, is described in the cat. Cats being fed a high protein vegetarian diet developed recurrent episodes of polymyopathy, characterised by ventroflexion of the head and neck, stiff forelimb gait, lateral head-resting and generalised muscle weakness. Plasma potassium concentrations (mean +/- standard deviation) were reduced from 3.28 +/- 0.33 mmol/l at the beginning of the experiment to 2.45 +/- 0.24 mmol/l during bouts of myopathy. This hypokalaemia was associated with increased creatine kinase activities indicative of muscle damage, and decreased urinary potassium concentrations, and was caused by insufficient dietary potassium. Cats that received the same diet supplemented with potassium did not develop hypokalaemic polymyopathy. Spontaneous recoveries of affected cats were not associated consistently with increases in plasma potassium concentrations. Plasma taurine concentrations decreased and glutamic acid increased markedly in all cats fed the experimental diet. There was no evidence of thiamin deficiency associated with the high glutamic acid intake. Veterinarians should be aware that hypokalaemic cats, and in particular those on potassium-deficient diets, may show cyclical disease with episodes of polymyopathy recurring after periods of spontaneous clinical recovery. This condition in cats may be a useful animal model for familial hypokalaemic periodic paralysis in humans.

Appendix III: Inadequate quality control in feed production: A case study

See also the associated debate about vegetarian feline diets in the J Amer Vet Med Assoc, 2005.

A study by Gray et al. (2004) well illustrates the need for sound quality control procedures during manufacturing. Two commercially available vegetarian cat foods were subjected to blind (labels removed) nutritional analysis by Woodson-Tenent Laboratories. Diet A (Vegecat KibbleMix) was prepared according to company instructions using vegetable oil, flour, tomato paste, and the supplied powdered dietary supplement for adult cats. Diet B (Evolution canned diet for adult cats) required no additional preparation.

The laboratory results were compared to Association of American Feed Control Officials (AAFCO) nutrient profiles for the maintenance of adult cats. The Committee on Animal Nutrition, reporting to the Board of Agriculture within the National Research Council (NRC), has developed nutrient requirement standards for at least fifteen specific species of animals. AAFCO historically used the NRC recommendations, but in 1993 began publishing its own expanded nutrient requirements. These are now widely recognized as the required nutritional standards for animal feeds.

The results of Gray et al.’s study are listed in Table 1.

Table 1: Nutritional content of two vegan feline diets


NutrientDiet ADiet BAAFCO nutritional requirements
Protein29.29 %25.40 %26 %
Crude Fat9.17 %15.33 %9 %
Tryptophan0.35 %0.29 %0.16 %
Methionine0.47 %0.33 %0.62 %
Threonine0.90 %0.84 %0.73 %
Valine1.16 %1.02 %0.62 %
Isoleucine1.03 %0.91 %0.52 %
Leucine1.80 %1.53 %1.25 %
Phenylalanine1.33 %1.09 %0.42 %
Lysine,total0.71 %1.20 %0.83 %
Histidine0.52 %0.47 %0.31 %
Arginine0.95 %1.49 %1.04 %
Taurine0.02 %<0.04 %0.10 %
Linoleic acid1.55 %3.72 %0.50 %
Arachadonic acid<0.01 %<0.02 %0.02 %
Calcium0.80 %0.06 %0.60 %
Phosphorus0.54 %0.28 %0.50 %
Selenium7 ppm0.48 ppm0.1 ppm
Niacin75.07 mg/kg39.97 mg/kg60 mg/kg
Retinol (Vit A)618631 IU/kg<1599 IU/kg5000 IU/kg
Pyroxidine3.28 mg/kg2.91 mg/kg4 mg/kg
Cobalamin0.31 mg/kg0.02 mg/kg0.02 mg/kg
All values represent dry matter (DM) proportions.

While both brands claimed nutritional completeness on their labels, as Table 1 demonstrates, both were in fact deficient in select amino acid composition, trace minerals, vitamins, and arachidonic acid. Diet B was also deficient in overall protein content.

Diet B was just barely deficient at 25.4 %, while Diet A was adequate at 29.29 %. The AAFCO requirement was 26 %. The study authors suggest that the AAFCO level may be inadequate (Gray et al., 2004). While unable to substantiate this suggestion, they cited the protein levels of Hill’s Pet Nutrition diets for comparison: 33.5 % protein DM for a feline maintenance diet, and 28.3 % protein DM for cats with renal failure (Hill’s Pet Nutrition, 2003). High protein diets have been used or suggested to control signs of diabetes mellitus (Frank et al., 2001), inflammatory bowel disease (Zoran, 2002) and to reduce obesity (Hannah, 1999). On the other hand, the excessive protein levels found in some meat-based commercial brands predispose to chronic renal disease. DiBartola et al. (1993) demonstrated renal lesions in an alarming 56 % (5/9) of cats exclusively fed a meat-based commercial diet containing 40 % DM protein for two years.

Amino acids
Both brands were deficient in taurine; Diet A contained 0.02 % and Diet B contained less than 0.04 %. The AAFCO requirement was 0.10 %. Both brands were deficient in methionine; Diet A had 0.47 % and Diet B contained 0.33 %. The AAFCO requirement was 0.62 %. Lysine and arginine were deficient in Diet A at 0.71 % and 0.95 %, respectively. The AAFCO requirements were 0.83 % and 1.04 %.

Arachidonic acid
Arachidonic acid was deficient in both diets as well; Diet A contained less than 0.01 % and Diet B contained less than 0.02 %. The AAFCO requirement was 0.02 %. Diet A utilized a species of seaweed, Ascophyllum nodosum, as an arachidonic acid source. The deficiency detected could be due to variations in arachidonic acid concentration between batches of seaweed. Available light and nutrients during seaweed growth and age at harvest may all affect nutrient availability (Peden, 2004).

Diet B was deficient in several B vitamins as well. Niacin was inadequate at 39.97 mg/kg and cobalamin was marginal at 0.02 mg/kg. The AAFCO requirements were 60 mg/kg and 0.02 mg/kg respectively. Both were deficient in pyroxidine; Diet A contained 3.28 mg/kg and Diet B contained 2.91 mg/kg. The AAFCO requirement was 4 mg/kg. Diet B was also deficient in retinol (vitamin A) at less than 1599 IU/kg. The AAFCO requirement was 5000 IU/kg.

Diet B was deficient in calcium (0.06%) and phosphorus (0.28%). The AAFCO requirements were 0.60% and 0.50% respectively. The Ca:P ratio was 0.21, as compared to an ideal of 1:1 to 2:1. A low ratio places cats at risk of nutritional secondary hyperparathyroidism and consequent loss of bone density. Interestingly, Diet A selenium levels of 7 ppm greatly exceeded the AAFCO requirement of 0.10 ppm. Selenium toxicosis has not been demonstrated in cats, although levels greater than 5 mg/kg are toxic to many other species (National Research Council, 1986).

Manufacturer response: Evolution Diet

In response to these results, Eric Weisman, Evolution Diet CEO (2004) stated, “We have ten to twenty thousand healthy and long living dogs, cats and ferrets living on the Evolution Diet. … Major animal sanctuaries use our products and stand behind them. These sanctuaries use our products because they have lower rates of illness and mortality when their animals are placed on our foods.”

Given that Gray et al.’s study illustrated that one tested Evolution Diet sample failed to meet the AAFCO nutrient profiles for maintenance of adult cats, one or more of the following possibilities must be true:

  • The sample tested was nutritionally inadequate, but the great majority of samples sold and used are adequate. This may have resulted from a formulation error at the factory or from degradation over time of a very old sample. However, it is unlikely that a very old sample would have been retained for testing.

  • The laboratory results were significantly in error for several nutrients tested. However, given a professional, accredited laboratory was used, and that the samples were tested blind to prevent bias, this seems very unlikely.

  • The AAFCO cat food nutrient profiles for the maintenance of adult cats are highly conservative, and, although Evolution Diet pet food does not meet the AAFCO requirements, it does meet the actual the nutrient requirements for the maintenance of the great majority of adult cats. However, this also seems unlikely. Even if only 10% of cats required the nutrient levels specified by AAFCO, given that “ten to twenty thousand healthy and long living dogs, cats and ferrets [live] on the Evolution Diet” (Weisman, 2004), this would have resulted in a minimum of several hundred cats showing signs of nutritional deficiency following chronic feeding on the Evolution Diet. An affected population this large would most probably be detected, yet it has not been.

Hence the most likely possibility is that the sample tested was nutritionally inadequate, but the great majority of samples sold and used are adequate, and that a formulation error occurred at the factory.

Manufacturer response: Harbingers of a New Age

James Peden, of Harbingers of a New Age (2004), stated in relation to their Vegecat KibbleMix:

“We were frankly shocked by the analysis of the kibble made from Vegecat KibbleMix. I talked with our mixing personnel about the report and tried to understand how such a situation could have occurred. I’m convinced that this particular batch of Vegecat KibbleMix was made improperly, and have stressed to our personnel the importance of paying attention to the mixing process and if any errors are made to notify me immediately rather than pass on incorrectly mixed product.

We will reformulate our products in light of these unsettling facts, and submit to a lab for analysis

The fact that we’ve supported so many healthy vegan cats for so many years indicates that this particular batch was an isolated incident. But still, this is very alarming and requires our immediate attention.

Probably this was a one-time event, and never happened again.

It is so unfortunate that Tina [Tina Gray, study author] analyzed an atypical batch of KibbleMix. … It probably only affected 14 pounds total, since that is the small amount we make per batch by hand!

One more thing we plan on doing soon. We have a larger facility that we are moving into for mixing, and it will make it possible to keep our raw ingredients and premixes better isolated and organized.”

“One note about the protein. In our directions we state that any wheat flour can be used. We will change that to read only whole wheat or bread flour. That adds 1% protein over the results that Tina achieved, since Tina used all purpose flour.”

Taurine and selenium
“We don’t even add selenium to the kibble formulation. The taurine that we obtain is crystalline and assays at 98.5% purity.

[The mixing person] brought to my attention what must have happened. He mistakenly picked up the Vegecat Micro-Mix container instead of the Vegecat KibbleMix MACRO. That substitution would have resulted in grossly elevated selenium levels as well as a complete lack of taurine, since only the MACRO contains the taurine, and not the Vegecat Micro-Mix.

It’s a relief to me to know what happened, and why the values are so off. What I’m going to do is put color coding on the containers that will match color coding on the wall charts.”

Amino acids and vitamins
”We depend to a large extent upon a food yeast for vitamins and amino acids. Apparently the nutrient profiles that we have for that raw material are in error. What we plan to do is add additional methionine, as well as add lysine, arginine, and pyroxidine (B6) to make up for the deficiency. We will add a preformed source of arachadonic acid, instead of depending upon the kelp to meet that requirement.

The excessive amounts of B12 and Vit A are alarming, and again I’ve stressed the importance of paying attention to the mixing process.”

As with the Evolution Diet, the same three possibilities exist to account for both Gray et al.’s study results, and the large existing population of healthy cats maintained on Vegecat KibbleMix. Once again, the most likely possibility is that the sample tested was nutritionally inadequate, but the great majority of samples sold and used are adequate, and that a formulation error occurred at the factory. This hypothesis was confirmed and the error corrected by the company.

The steps described to rectify the nutritional inadequacies identified by Gray et al. are reassuring. As with Evolution Diet cat food, ultimate confirmation would be provided by repeatable independent laboratory analyses. By August 2004 no such confirmatory results were available.


Gray et al.’s 2004 study illustrates the need for good quality control during production to ensure that feed products consistently meet the nutritional requirements specified by authorities such as AAFCO, and intended by their manufacturers. It is entirely feasible that repeated independent laboratory analyses of a range of commercial brands, both vegetarian and meat-based, would similarly demonstrate nutritional inadequacies, and also inconsistency of nutritional content over time.

Such findings in no way negate the ability of well formulated vegetarian or meat-based diets to meet all the nutritional requirements of the normal animals for which they are intended; they simply demonstrate the consequences of inadequate quality control, and the need for sound quality control systems during manufacture, including regular laboratory nutritional analyses.