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Vegetarian Canine Diets

Andrew Knight BSc. (Vet. Biol.), BVMS, MRCVS

Veterinarian

www.AnimalConsultants.org

Updated: 13 Jul. 2008

CONTENTS
 

1.      Introduction

2.      Requirements of vegetarian diets

3.      Palatability

4.      Nutritional content

5.      Bioavailability

6.      Health survey

7.      Urinary alkalinization

8.      Health benefits of vegetarian diets

9.      Conclusions

References

1.    Introduction

The enormous death and suffering inflicted upon approximately fifty billion chickens, pigs, sheep, cows, and other animals, both intensively and extensively farmed, who are slaughtered annually, and upon millions of intensively farmed or wild-caught fish, in order to fulfill the desire of some human beings for meat, has been thoroughly documented; as have the deleterious environmental impacts of both intensive and extensive animal farming (www.VeganOutreach.org provides extensive, thoroughly-referenced information on these issues).

It is because of the ethical concerns of a growing population of vegetarian animal guardians, and because of medical conditions such as allergies which are caused by beef, lamb and other meat-based dietary ingredients, that vegetarian pet food brands were first developed. However, canine vegetarian diets remain the subject of some controversy, which is exacerbated by ignorance of the health and nutritional issues involved, including among veterinarians and other experienced animal carers.

To assist animal guardians, animal carers and veterinary personnel who wish to gain a sounder understanding of these issues, the following examines the palatability, nutritional and bioavailability requirements of vegetarian canine diets; provides the results of a survey of the health status of 300 vegetarian dogs; provides advice on the prevention of urinary alkalinization, blockages and infections, to which a small percentage of vegetarian dogs are predisposed; and describes the health benefits commonly observed in dogs upon switching to a nutritionally sound vegetarian diet.

2.    Requirements of vegetarian diets

Whatever combination of animal, plant, mineral or synthetically-based ingredients are used, diets should be formulated to meet the palatability, nutritional and bioavailability requirements of the species for which they are intended.

3.    Palatability

The fixation of some dogs to meat-based commercial brands to which they have become accustomed is primarily due to the addition of ‘digest,’ the industry euphamism for partially digested chicken entrails. According to Small Animal Clinical Nutrition, “Digest is probably the most important factor discovered in recent years for enhancing the palatability of dry food for cats and, to a lesser degree, dogs.” (Lewis et al., 1987).

Although less of a problem than in cats, patience and persistence may be required when altering the diets of some dogs who have been exposed to digest long-term. In difficult cases it may first be necessary to withhold all food (not water!), for one day. This will stimulate the appetite without harming the dog. It may be necessary to change the diet gradually, e.g. by using 90 % old and 10 % new diet for a few days, then switching to 80 % and 20 % for a few more days, thereby transitioning to the new diet over several weeks, or even longer if necessary. A gradual change is more acceptable behaviorally in difficult cases, and also allows an appropriate transition of digestive enzymes (to the extent possible) and intestinal flora (bacteria), thereby minimizing the chance of gastrointestinal reactions such as diarrhea.

Dog guardians should demonstrate by their behavior that they consider the new diet just as edible as the old (without possibly warning or alarming the dog by making a fuss). They should not be concerned if their dog eats around the vegetarian food at first; just having it in close proximity to the other food will help the dog make the necessary mental association. Mixing the food thoroughly may help, as may the addition of odiforous (the sense of smell is very important) and tasty additives, such as nutritional yeast, vegetable oil, nori flakes and spirulina. Gently warming the food may also help. Guardians should remove uneaten food and offer only fresh food.

The most important factors for difficult dogs are gradual change and persistence. Using these principles, the most stubborn of dogs have been successfully weaned onto healthy vegetarian diets. Vegetarian dog food recipes may be obtained from Peden (1999) and Gillen (2003) and from suppliers www.VegePet.com and www.VeganCats.com.

4.    Nutritional content

Dogs may be biologically classified as omnivores, due to their ability to subsist on a mixed diet of animal and plant-based material in their natural environments. They are less adapted to a carnivorous diet than cats, and their nutritional needs are easier to meet on a vegetarian diet.

Nevertheless, to safeguard health and avoid cardiac or other diseases, vegetarian diets must be complete and balanced with respect to all essential nutrients. This may be achieved by feeding a vegetarian nutritional supplement or complete commercial diet certified on the label as meeting the nutritional standards of the US Association of American Feed Control Officials (AAFCO).

The Committee on Animal Nutrition, reporting to the Board of Agriculture within the US National Research Council (NRC), has developed nutritional standards for at least 15 species. Historically AAFCO used the NRC recommendations, but in 1993 began publishing its own expanded nutrient requirements, which are now widely recognized as the required nutritional standards for animal feeds.

In order to meet AAFCO nutritional requirements, manufacturers of vegetarian (and, in some cases, processed meat-based diets), diets rely upon vegetable, mineral and synthetic sources of nutrients normally derived from animal tissues.

5.    Bioavailability

The bioavailability of nutrients (extent to which they are available to the tissues) is determined largely by their level of digestibility into simple molecules capable of absorption through the intestinal mucosa. The importance of digestibility is increased in animals such as cats and dogs that have relatively short intestinal tracts. Fortunately, studies have demonstrated ample digestibility of vegetarian dietary ingredients in cats and dogs.

The digestibility of some sources of protein has been evaluated in the dog. Hegsted et al. (1947) found that the apparent digestibility of proteins in an all vegetable diet containing white bread, corn, rice, potatoes, lettuce, carrots, onions, tomatoes and applesauce was 80.0 (plus or minus 7.7 %). James and McCay (1950) reported that the apparent protein digestibility of commercial, dry-type food, containing both vegetable and animal proteins, ranged from 67 to 82 % for adult dogs. Kendall and Holme (1982) reported the apparent crude protein (Nx6.25) digestibility coefficients for textured soy protein, extracted soy meal, full-fat soy flour, and micronized whole soybeans ranged from 71 to 87 %. Moore et al. (1980) reported apparent digestibility values of soybean meal, corn, rice, and oats by mature Pointers to be in the range of 77 to 88 %. Their data revealed that normal cooking  procedures did not significantly influence the digestibility of rice, oat, or corn protein. Their data also indicated that increasing the fat content of the diet from 10 to 20 % did not alter the digestibility of nitrogen in a corn-soybean-based diet. Burns et al. (1982) showed that the apparent digestibilities of lactalbumin, casein, soy protein, and wheat gluten are 87, 85, 78, and 77 %, respectively (National Research Council, 1986; 12). Clapper et al. (2001) compared the canine digestibility of five soybean protein sources to that of poultry meal, and found the soy protein to offer a viable protein source. They stated, "Soy protein, when combined with other protein sources that contain complementary amino acids, can provide an economical source of highly available and consistent-quality protein to the canine."

Pencovic and Morris (1975) studied the apparent digestibility of starch (added at 35 % of diet dry matter) found in corn or wheat grain. Apparent starch digestibilities for coarsely ground, finely ground, or coarsely ground and cooked grains were: corn, 79, 94, and 88 %; and wheat, 92, 97, and 96 % respectively. It was concluded that starch from corn and wheat, especially when finely ground, is well utilized by the cat (National Research Council, 1986; 6).

Pet food manufacturers are well aware of the acceptable digestibility of plant-based ingredients, which make up a large proportion of the products they sell.

6.    Health survey

In 1994 People for the Ethical Treatment of Animals (PETA) conducted a systematic survey of the health of 300 vegetarian dogs sourced from 33 US states and Canada via PETA’s newsletter (PETA, 1994). Dogs ranged in age from young puppies to 19 years old. 88.7 % (266/300) were spayed or castrated, and, of those who were not, 22 were male and 12 female. 52.7 % (158/300) were female and 47.3 % (142/300) male. 55.7 % (167/300) were mixed breeds and 44.3 % (133/300) were purebred, with a wide range of breeds represented, although a larger number of terriers (22), retrievers (22), beagles (7), and dobermans (6) were present. 65.3 % (196/300) were vegan (pure vegetarian—diets exclude eggs, milk and other animal products), with the remaining 34.7 % (196/300) simply vegetarian (ovo-lacto-vegetarians).

Table 1 illustrates the breakdown of vegans and vegetarians by the length of time they maintained a meatless diet:

Table 1: Duration of vegetarian and vegan diets of 300 dogs.

Overall health status

There appeared to be a distinct advantage to being a vegan or vegetarian for a larger percentage of one's life—all of the following percentages are greater than for the entire surveyed population:

There also appeared to be a slight health advantage for veganism compared to vegetarianism: 82 % of dogs who had been vegan for five years or more were considered to be in good to excellent health, while only 77 % of dogs who had been vegetarian for five years or more were considered to be in good to excellent health.

Deaths

Twenty eight deceased dogs were included in the survey. Excluding the three dogs who either died in accidents or were euthanized for aggression, the median age of death was 12.6 years. The average length of time as a vegan or vegetarian was 5.7 years. The causes of death are summarized in Table 2:

Table 2: Causes of death of 28 dogs.

Miscellaneous causes of death included: renal, spinal, liver cirrhosis, euthanasia due to arthritis, and unknown causes.

Incidence of health problems

1.       INFECTIONS

Overview

The most common health problem was infections of all kinds. 11.7 % (35/300) suffered some type of infection, with ear infections being the most common (16), followed by urinary tract infections (eight), eye infections (six), and other miscellaneous infections (seven). There was an inverse relationship between length of time as a vegan or vegetarian and incidence of infections:

·          No dog who had been vegan for four or more years or vegetarian for more than 5.2 years contracted ear, urinary tract, eye or other infections.

·          No dog who had been vegan for more than 3.5 years had an ear infection.

·          No dog who had been vegetarian for more than four years had a urinary tract infection.

Urinary Tract Infections

2.7 % (8/300) dogs had a history of urinary tract infections, of which six were female and two male. According to a veterinarian contacted by PETA, this figure is somewhat higher than the expected rate of infection (about 1%).

The excretion of the nitrogenous waste products of protein catabolism results in the acidic urine of carnivores. Vegetarian diets with their decreased protein content result in urinary alkalinization, which increases the risk of urinary stones, which may result in partial or complete urinary obstruction (which may be life threatening). Alterations in bacterial flora, with increased possibility of urinary infections, may also result (see 'Urinary Alkalinization' below).

2.       SKIN PROBLEMS

The second most common health problem observed after infections was skin ailments, which also constitute the most common illnesses of dogs overall. 11.3 % (34/300) suffered from some form of skin irritation (hot spots, flea allergy, dermatitis, etc.), but eight of these were considered to be minor.

3.       ARTHRITIS

The third-ranking health problem was arthritis, with 7.3 % (22/300) suffering from this condition. Seven of the 22 dogs had arthritis related to old injuries, such as broken bones. Of the remaining 15 dogs, 13 were 10 years old or older.

4.       BENIGN GROWTHS

4.7 % (14/300) had benign growths, tumors, warts, or cysts, which appeared unrelated to time spent on a vegetarian diet.

5.       HEART PROBLEMS

4.0 % (12/300) had heart problems, and seven of the 12 had died as a result of those problems. Five of the dogs who died of heart problems were 13 to 15 years of age, which is not unusual. However, the trend for heart disease was the opposite of that for infections, i.e., there was a direct correlation between heart disease and length of time as a vegan or vegetarian: all dogs with heart disease had been vegan for at least four years or vegetarian for at least 10 years.

The most common and serious cardiac disease was dilated cardiomyopathy (DCM). Five dogs (aged five, nine and older), all of whom had been vegan for at least four years, had DCM, which results in myocardial (heart muscle) flaccidity and impaired pumping ability. This potentially fatal disease of the heart muscle normally affects about 2 % of all dogs, appearing mostly in large and giant breeds. A small percentage of these lack sufficient cardiac levels of the amino acid L-Carnitine. The amino acid taurine, which dogs, unlike cats, are able to synthesize, regulates the entry of calcium into the myocardium in order to trigger each heart beat. Deficiency may also result in cardiomyopathy (heart muscle disease).

However, recovery is possible with taurine or L-carnitine supplementation. Of the five dogs with DCM, three recovered by taking supplements of either L-carnitine or taurine. Prevention appears possible through regular supplementation with these two amino acids, via a nutritionally complete vegetarian canine supplement.

6.       OVERWEIGHT

A low 3.7 % (11/300) were considered by their guardians to be overweight. However, all 11 dogs were nevertheless described as in good to excellent health or energetic. The decreased protein and fat levels and increased dietary fiber of vegetarian diets are all effective in promoting a healthier weight.

7.       DIGESTIVE PROBLEMS

3 % (10) were identified as having digestive problems. Of these, nine were seven years or older, which may have been related to a general decline in digestive enzyme secretion with age, and which is often treatable with enzyme supplementation.

8.       HYPOTHYROIDISM

2.7 % (8/300) had hypothyroidism, a decrease in serum thyroid hormone levels. However, no dog who had been vegan for more than three years had hypothyroidism, and no dog who had been vegetarian for more than four years suffered from it.

9.       DEAFNESS AND HEARING LOSS; BLINDNESS OR VISION LOSS

2.7 % (8/300) were deaf or had hearing loss, but seven of the eight were 13 years old or older. Similarly, seven dogs (2.3 %) were blind or had vision loss, but six of the seven were 13 years old or older. Age-related hearing and vision loss is normal. The younger blind dog was a collie with congenital blindness.

10.    CANCER

A low 2.7 % (8/300) had cancer. Of these eight, six were 9 years old or older, with the other two being seven years old. The incidence of cancer normally rises with age. The inverse correlation between duration of vegan or vegetarian diet and cancer incidence appears significant: no dog who had been vegan for more than five years and no dog who had been vegetarian for more than 5.5 years had cancer.

Specific Foods

NUTRITIONAL YEAST AND GARLIC

Dogs eating nutritional yeast and/or garlic did seem to fare somewhat better than the rest of the dogs. 81.6 % (102/125) of the dogs eating nutritional yeast were in good to excellent health, compared to 72.6 % of those who did not. 83.3 % (70/84) of dogs eating garlic were in good to excellent health, compared to 80 % of those who did not. Dogs eating either nutritional yeast or garlic also had a much higher incidence of good or improved coats—44 % for nutritional yeast eaters and 47.6 % for garlic eaters, compared to only 22.9 % of dogs not eating nutritional yeast and 17.8 % of dogs not eating garlic.

SOY FOODS

The only other specific food item that seemed significant was soy food products. Since all the commercial vegetarian dog foods eaten contained soy, very few dogs had no soy products in their diets—only 13 % (39/300). However, these 39 dogs were in substantially better health than the others. 89.7 % (35/39) of the dogs who ate no soy products were in good to excellent health, compared to 74.3 % of dogs who ate soy products. Also, the incidence of skin problems was much lower in the dogs who didn’t eat soy—only 5.1 % (2/39) had skin problems compared with 10.7% of those who ate soy products. Dogs who did not eat soy products relied heavily on grains (oats, rice, bread, and pasta), legumes (chick peas, lentils, split peas, and beans), vegetables, potatoes, and sunflower seeds.

Conclusions 

The results suggest that:

 

·          The longer a dog remains on a vegetarian or vegan diet, the greater the likelihood of overall good to excellent health.

·          Veganism is more beneficial than vegetarianism.

·          The longer a dog remains on a vegetarian or vegan diet, the less likely he or she is to get cancer, infections, hypothyroidism, or suffer from obesity.

·          A vegetarian diet may increase urinary alkalinization, with its consequent potential for urinary stones, blockages and infections; hence regular urine pH monitoring and correction of alkalinization is important.

·          The longer a dog remains on a vegetarian or vegan diet without supplementation of L-carnitine or taurine, the greater the likelihood of dilated cardiomyopathy or other cardiac disease.

·          Nutritional yeast and garlic appear beneficial to overall health and coat condition.

·          Dogs without soy foods in their diet appear healthier than those who eat soy.

 

7.    Urinary alkalinization

The excretion of the nitrogenous waste products of protein catabolism results in the acidic urine of carnivores. Vegetarian diets with their decreased protein content result in urinary alkalinization. These results were confirmed via a survey of 33 dogs (PETA, 1994):

 Table 3: pH of urine of 33 dogs

Source: PETA, 1994.

42 % (14/33) had alkaline urine (pH > 7.0). 15.2 % (5/33) had a history of urinary tract infections, but two of these five had pHs of 6.2 and 6.8 respectively. 78.6 % (11/14) of the dogs with alkaline urine had no history of urinary tract infections (PETA, 1994).

Although dogs are seemingly less predisposed than cats, urinary alkalinization can result in the crystallization of urinary salts, resulting in the formation of stones in the urinary system (urolithiasis), which may result in partial or complete urinary obstruction (which may be life threatening), dysuria (difficulty in urinating) and haematuria (blood in the urine). Alterations in bacterial flora, with increased possibility of urinary infections, may also result.

The likelihood of alkalinization, urolithiasis, and urinary tract infections may be minimized via several means:

Minimizing magnesium content

By far the most common urinary stone (urolith) is struvite (magnesium-ammonium-phosphate) (Blood & Studdert 1988). Hence minimizing dietary magnesium concentrations minimizes urinary magnesium concentrations, decreasing struvite formation. Magnesium concentrations may be available on product labels.

Water consumption

Urinary salt concentrations can also be lowered by increasing the volume of water drunk and excreted. Clean, fresh water should always be available, and salty foods or a pinch of salt added to normal wet food are of benefit in stimulating thirst.

Urinary acidifiers

The normal pH of dog urine slightly acidic, with struvite requiring 7.0 or higher to crystallize (Gillen, 2003). Urine may be acidified in several ways.

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, coconuts and macadamia nuts), grains (not millet), and wheat gluten (used in kibble recipes) may be included in vegetarian dog food, and are all urinary acidifiers (Peden, 1999).

Vitamins are also of benefit. Vitamin C (ascorbic acid) is a urinary acidifier. Tablets may be pulverized or ascorbic acid powder may be used. The BSAVA (British Small Animal Veterinary Association) Small Animal Formulary (drug handbook) recommends a dosage of 50-80 mg/kg every 24 hours for cats and dogs (Tennant, 2003). pH buffering negates their effectiveness, so unbuffered Vitamin C should be used. If other urine acidifiers are also used, doses may be decreased.

Methionine is particularly effective in preventing struvite formation. Methionine is metabolized into sulfuric acid which is a powerful urinary acidifier. Additionally, sulfate displaces phosphate from the magnesium-ammonium-phosphate complex, preventing struvite formation. The BSAVA Small Animal Formulary recommends a dosage of 200 - 1,000 mg/dog every 8 hours (Tennant, 2003). The dosage should be adjusted to maintain urine pH at or below 6.5. Excessive methionine levels can result in metabolic acidosis with consequent loss of bony calcium and electrolyte imbalances (Peden, 2003). Methionine should not be used in young animals nor those with kidney or severe liver disease (Tennant, 2003).

Sodium bisulfate is a particularly powerful urinary acidifier, and is added to some vegetarian pet nutritional supplements (Peden, 2004). Ammonium chloride is also a powerful urinary acidifier, but may decrease palatability. In his "5-minute (veterinary) consult drug formulary," Papich (2004) recommends a dosage of 100 mg/kg every 12 hours.

Prevention

Dogs are less predisposed to urinary problems than cats, and although adverse health consequences are unlikely, those consequences may include fatal blockage of the urinary system, particularly for males; and painful urinary tract infections. Hence urinary pH and dietary magnesium concentrations should be monitored. To ensure safety, urinary pH levels of both males and females should be checked in the beginning, and at least fortnightly during transition to a vegetarian diet, and every 3 months thereafter, for life - even once diet and pH levels appear to have stabilized. Levels should be checked more frequently during any dietary, environmental or other changes with the potential to result in destabilization. Urine can be collected from dogs using containers such as foil baking trays. pH test strips are also available from veterinarians, although pH meters provide the most accurate results.

Gillen (2003) describes three steps, in increasing order of magnitude, that may be taken to rectify urinary alkalinization, if detected. He applies these steps to cats, but the general principles are also applicable to dogs: 

1.        For minor cases, he states that enzyme supplements which include methionine, vitamin C, and/or cranberry extract will be sufficient. These limit both urinary alkalinization and inflammation. They also aid digestion, and can result in increased vitality.

 

2.        For moderate cases, Gillen states that vegetarian nutritional supplements with added sodium bisulfate may be sufficient.

 

3.        For severe cases Gillen recommends methionine pills.

8.    Health benefits of vegetarian diets 

As of 2005, an English border collie is well on the way to becoming the world’s oldest dog. Bramble “loves exercise” and “has a real passion for being outdoors,” according to her guardians. One stated, “She can be a thorn in my side when she's restless, but it's what keeps her going.” At the age of 27 (189 in human years), Bramble is still “alert and active and goes for a walk four times a day,” and swims once a week. Bramble subsists mainly on a diet of rice, lentils and organic vegetables. Bramble is vegan (pure vegetarian, consuming no animal products at all) (Anonymous, 2005).

Apart from the increased overall health, and decreased incidences of cancer, infections and hypothyroidism among the 300 dogs surveyed by PETA (see Health Survey previously), numerous other happy guardians of vegetarian dogs have reported their experiences in Peden’s (1999) Vegetarian Cats & Dogs. The health benefits they reported include decreased ectoparasites (fleas, ticks, lice and mites), improved coat condition, allergy control, weight control, decreased arthritis, improved vitality, improved stool odor and cataract resolution.

Ectoparasites and coat condition

Alison Shepard wrote of her dogs Vanya and Vladimir: “Vanya (age 10) and her son, Vladimir (age 5) have always been vegetarian. Since we’re going to breed Vladimir, we had his hips X-rayed for certification. He got “excellent” rating from O.F.A. — top score! He and his mom have beautiful coats and skin. Here in Florida, skin problems are very common — hot spots, etc. Also, they don’t seem to attract fleas. People assume we “bomb” our house & soak our yard with pesticides, like everyone else seems to. They can’t believe the answer is diet.” (Peden, 1999).

Veterinarian Richard Pitcairn (Pitcairn & Pitcairn, 1982) quoted a New Yorker: “Friends think I’m nuts to cook for a dog. They have younger dogs with loose or missing teeth, severe rashes, heart and breathing problems, overweight, lethargy, etc. They say Buck is so healthy because he’s a mutt. That might help, but I think the diet and care he gets is part of it also. Buck has never had fleas either.”

Allergy control

Possibly assisted by the proliferation of artificial dyes, flavorings, preservatives (especially ethoxyquin), stabilizers and adulterated slaughterhouse products in commercial meat-based pet foods, the prevalence of companion animal allergies is rising. As stated by allergy expert and veterinarian Dr Alfred Plechner, animal products provoke the most allergic reactions, with beef at the top of the list for both cats and dogs. Changing to another commercial meat-based pet food usually does not resolve the problem, because of the similarity in ingredients used (Plechner & Zucker, 1986). Consequently several meatless Hills Canine Prescription Diets (k/d, dry u/d, dry d/d, and dry s/d) have been formulated to address allergies and degenerative medical conditions.

Itchiness is the most common sign of a food allergy for companion animals, although vomiting, coughing or wheezing can also be present.

Michael Buzel of Florida recounts the story of his dog, Penny: “I adopted my first dog, Penny (collie/golden retriever mix) from the Florida Broward County Humane Society in 1987. She was four and one-half years old and suffered from multiple allergies that caused her to scratch constantly and gnaw at her backside. She kept losing a lot of hair and generally did not look very happy. I brought her to my first veterinarian who gave her cortisone pills that alleviated the problems. Unfortunately, cortisone causes other problems that are worse in the long run. When she stopped taking the pills, the problems recurred. I thought there has to be a better remedy than medication, so I found another veterinarian who suggested changing her diet. We eliminated all allergic foods (meat, chicken, fish, eggs, yeast, milk, etc.) using a commercial dry and canned dog food. It still contained lamb but Penny’s condition dramatically improved. ….A friend told me about Vegedog and gave me a recipe for a vegetarian dog food (using a lentil base) and told me to supplement it with Vegedog. Penny loves the food and I feel good about the food I’m feeding her. I cook the food every other Saturday morning (it takes approximately two hours start to finish) using two large stock pots. I make a lot because I recently adopted another dog in need of a home (golden retriever) that became a vegetarian when he became a member of my family. I never cooked in such large quanti