Nutritional modulation of disease is currently an area of great interest. Optimal diets for patients with various diseases have not been fully defined and likely vary depending on individual patient factors, along with clinical signs and clinicopathologic abnormalities. However, dietary modification potentially could provide great benefit in the management of patients with various diseases.
Several pet food companies manufacture therapeutic diets for dogs and cats that are designed to aid in the management of various diseases, such as renal, hepatic, cardiac, and dermatologic disease. Although only a few studies have evaluated how many dogs and cats with various diseases are being fed a therapeutic diet, it appears that the numbers are low. A study1 of 82 dogs with cardiac disease, for instance, found that only 4 were being fed a diet specifically formulated for dogs with cardiac disease. The American Animal Hospital Association's 2002 Compliance Study2 found that only 19% of dogs and 18% of cats with specific diseases were being fed therapeutic diets.
There are many reasons why any particular dog or cat with a specific disease is not being fed a therapeutic diet formulated for animals with that disease. It may be that a therapeutic diet has not been recommended by the attending veterinarian; the owner has chosen not to feed a therapeutic diet; the animal has refused to eat the diet; or the animal's clinical signs, laboratory findings, or concurrent diseases make feeding a therapeutic diet less desirable. Nevertheless, the apparently low proportion of dogs and cats with various diseases that are fed therapeutic diets is puzzling.
Dietary supplement use is another important aspect of nutritional modulation. Dietary supplement use is widespread in people, with > 50% of adult Americans taking 1 or more dietary supplements.3,4 Dietary supplement use is more common in women than in men and is associated with level of education, other health behaviors, and age.4–6 In a previous study,7 > 70% of elderly people were reported to use dietary supplements, and use of dietary supplements is more common in people known to have a disease than in the general population. For example, a study8 of children with various chronic diseases found that 62% used dietary supplements, with only about half of these supplements having been prescribed by a healthcare provider. In a study1 of dogs with cardiac disease, 31% were receiving dietary supplements, with multivitamins, coenzyme Q10, l-carnitine, taurine, and fatty acids being the most common supplements. However, little information on dietary supplement use in dogs and cats is available.
Disease prevalence is an important consideration when determining the proportion of dogs and cats receiving therapeutic diets and dietary supplements. In the largest study9 to date on disease prevalence in small animals, 46,710 dogs and cats examined at private veterinary practices in the United States were evaluated and the most common diseases for both dogs and cats were dental disease and dermatologic disorders. However, this study was limited to dogs and cats being evaluated at a veterinary clinic. Therefore, the results may overestimate the true prevalence of disease among dogs and cats in the general pet population.
Information regarding disease prevalence in the general pet population and the proportions of dogs and cats receiving therapeutic diets and dietary supplements would assist veterinarians making dietary recommendations for patients with various diseases and facilitate communication with pet owners. Therefore, the purposes of the study reported here were to estimate disease prevalence among dogs and cats in select areas of the United States and Australia and determine the proportions of dogs and cats in those areas that receive therapeutic diets or dietary supplements.
Materials and Methods
The present study was designed as a part of a larger telephone survey conducted to obtain information about pet health status, pet-owner interactions, feeding habits, and owner attitudes toward their pets.a Questions specific to the present study related to the prevalence of various diseases in dogs and cats and the proportions of dogs and cats receiving therapeutic diets and dietary supplements. Questions related to signalment, health status (ie, healthy, generally healthy, or unhealthy), and body condition (scored from 1 to 5, where 1 = emaciated, 3 = ideal, and 5 = obese) were also included. Owners who indicated that their dog or cat had a disease or who reported that they were feeding a therapeutic diet or providing a dietary supplement were asked to provide additional information through open-ended questions. Where required by an institution, the experimental protocol was reviewed and approved by the institutional review board of that institution.
The telephone survey involved individuals in 5 geographic areas: Davis and Sacramento, Calif; Lansing and East Lansing, Mich; Philadelphia, Pa, and Morris County, New Jersey; Boston, Mass; and Brisbane, Queensland, Australia. The local residential telephone directory for each of these areas was obtained, and a defined randomization process was used to generate a list of telephone numbers to be called. First, the total number of pages in each telephone directory was divided by 100, and the result was rounded to the nearest whole number. This number was used as the spread between pages. Next, a number less than this previous number was randomly selected and used as the starting page. Beginning with this starting page and using the defined spread between pages, individual pages in each telephone directory were identified (eg, using a starting page of 10 and a spread of 8, consecutive pages in the telephone directory would be 10, 18, 26, etc). For each telephone directory page so identified, the number of columns on the page and the number of names in each column were counted and 5 sets of random numbers, with each set consisting of 1 number for the column and 1 number for names in the column, were generated (eg, 1:13 = 1st column, 13th name in column). These 5 sets of random numbers were then used to identify 5 names and telephone numbers on each directory page for use in the study (approx 500 names/telephone directory). Individuals identified through this process were contacted by telephone and invited to complete the survey. The randomization process was repeated with new random numbers as necessary for each telephone directory, with a goal of obtaining 200 completed surveys from each site.
Individuals contacted by telephone were eligible to participate in the survey if they owned at least 1 dog or cat. For households with > 1 dog or > 1 cat, the owner was asked to select a single pet as the subject of the survey. For households with both dogs and cats, a computerized, randomized, 2-treatment (dog and cat) list was used to determine whether the owner was asked to select a dog or cat in the household as the subject of the survey.
Telephone surveys were administered by 1 or more trained individuals at each study site. The survey took approximately 15 to 20 minutes to complete.
Statistical analysis—Data are reported as median and range. Categorical variables (eg, proportions of dogs vs cats receiving dietary supplements) were compared with χ2 analysis. All analyses were performed with standard softwareb; values of P < 0.05 were considered significant.
Results
Between May and August 2004, a total of 18,194 telephone calls were made. Of these, 1,104 (6%) were to individuals who owned at least 1 dog or cat and agreed to participate in the study. Subjects of the survey included 635 dogs and 469 cats. Median age of the dogs and cats included in the study was 5 years (range, 1 month to 21 years). There were 543 males (462 castrated) and 561 females (507 spayed).
When asked about their pets' health, owners responded that their pets were healthy (n = 886 [80%]), generally healthy but with minor or occasional problems (204 [19%]), or unhealthy (14 [1%]). However, owners of 176 (16%) animals indicated that their pets had 1 or more diseases. When owners were asked to identify specific disorders their pets had, the most common responses were musculoskeletal disease (n = 45), dental disease (26), gastrointestinal tract or hepatic disease (14), cardiac disease (12), lower urinary tract disease (12), blindness or other ocular disease (11), neurologic disease (10), and infectious disease (10; Table 1). When owners were asked to indicate body condition of their pets, 7 (0.6%) indicated a body condition score of 1 (emaciated), 55 (5%) indicated a score of 2 (slightly underweight), 686 (62.1%) indicated a score of 3 (ideal), 289 (26.2%) indicated a score of 4 (slightly overweight), and 67 (6.1%) indicated a score of 5 (obese).
Health conditions reported by owners of 635 dogs and 469 cats participating in a telephone survey.
| Condition | Total | Dogs | Cats |
|---|---|---|---|
| Musculoskeletal disease | 45 | 40 | 5 |
| Dental disease | 26 | 15 | 11 |
| Gastrointestinal tract or hepatic disease | 14 | 6 | 8 |
| Cardiac disease | 12 | 7 | 5 |
| Lower urinary tract disease | 12 | 2 | 10 |
| Blindness or other ocular disease | 11 | 10 | 1 |
| Neurologic disease | 10 | 9 | 1 |
| Infectious disease | 10 | 5 | 5 |
| Neoplasia | 9 | 7 | 2 |
| Dermatologic disease | 8 | 8 | 0 |
| Deafness or other otic disease | 8 | 8 | 0 |
| Other endocrine disease | 8 | 4 | 4 |
| Diabetes mellitus | 7 | 0 | 7 |
| Allergic disease | 6 | 4 | 2 |
| Renal disease | 6 | 1 | 5 |
| Respiratory tract disease | 3 | 2 | 1 |
| Obesity | 3 | 2 | 1 |
| Abscess | 1 | 0 | 1 |
| Behavior problem | 1 | 1 | 0 |
| Not stated | 21 | 14 | 7 |
A total of 108 dogs and 70 cats were reported to have 1 or more health conditions.
Twenty-eight (2.5%) owners reported that they were feeding a therapeutic diet prescribed by a veterinarian to manage a specific disease or with specific nutritional properties. Therapeutic diets being fed included diets for animals with renal disease (n = 5), lower urinary tract disease (3), dental disease (3), diabetes mellitus (2), or hepatic disease (1); reduced-calorie diets (5); reduced-fat diets (4); novel protein or hypoallergenic diets (2); a high-calorie diet (1); and a diet formulated for growth (1). One owner did not identify the type of therapeutic diet being fed. Twentyone of the 28 owners feeding a therapeutic diet considered their pets to be generally healthy, 5 considered their pets to be healthy, and only 2 considered their pets to be unhealthy. Animals reported to have a disease (21/176 [12%]) were significantly (P < 0.001) more likely to be receiving a therapeutic diet than were animals not reported to have any disease (7/928 [1%]).
Animals being fed a therapeutic diet were excluded from further data collection. Thus, information on dietary supplements refers only to the 1,076 animals not fed therapeutic diets. Owners of 107 of these 1,076 (9.9%) animals reported administering dietary supplements to their pets. Seventy (6.5%) indicated they administered supplements on a regular basis, and 37 (3.4%) indicated they administered supplements on an occasional basis. The proportion of dogs receiving supplements (82/624 [13.1%]) was significantly (P < 0.001) higher than the proportion of cats receiving supplements (25/452 [5.5%]). Animals reported to have a disease were significantly (P = 0.002) more likely to receive dietary supplements (26/155 [16.8%]) than were animals not reported to have any diseases (81/921 [8.8%]). Dietary supplements that were administered included multivitamins (n = 53); chondroprotective agents (22); fatty acids (13); vitamin C (7); calcium (6); antioxidants (5); combination products (4); yeast (3); taurine (2); zinc (2); and enzymes, herbs, charcoal, lysine, melatonin, garlic, and dimethylglycine (1 each).
Discussion
Results of the present study suggest that the prevalence of disease among dogs and cats in the United States and Australia is low. Surprisingly, although 176 (16%) owners indicated that their dog or cat had a disease, only 14 (1%) owners considered their pet to be unhealthy. This disease prevalence is lower than that reported in a previous study9 of animals examined at private veterinary practices in the United States, which found that 93% of dogs and 90% of cats had at least 1 disease condition. This difference is likely attributable to the fact that the previous study involved dogs and cats examined at veterinary practices, whereas the present study included randomly selected dogs and cats in the general population.
Only a small proportion of dogs and cats in the present study (2.5%) were reportedly being fed a therapeutic diet, and only 12% of animals reported to have a disease were being fed a therapeutic diet. The 5 most commonly reported diseases in the present study (ie, musculoskeletal, dental, gastrointestinal tract or hepatic, cardiac, and lower urinary tract disease) are all thought to benefit from dietary modification. However, few of the animals with these diseases were being fed therapeutic diets. Additional research evaluating the benefits of dietary modification in disease is needed, as is more information on client communication regarding dietary modification and adherence to recommendations.
Surprisingly, although owners of 356 (32.3%) animals in the present study indicated that their pets were slightly overweight or obese, only 3 of these owners considered this to be a health problem. However, dog and cat owners are not alone in this lack of recognition of obesity as a healthy problem. In a previous study,9 veterinarians routinely did not recognize obese dogs and cats as having a health problem, even when body condition scores were available. In that study, veterinarians reported that only 2.0% of dogs and 1.8% of cats were obese, when in fact, 28.3% of dogs and 27.5% of cats were assigned a body condition score that corresponded with overweight or obese. Greater emphasis on educating veterinarians and pet owners on the risks of obesity and on methods to prevent and treat it is needed.
The rate of dietary supplement use in the present study was lower than rates reported for humans, with only 9.9% of animals receiving dietary supplements. Use of dietary supplements was more common in dogs than in cats, possibly because of differences between dog and cat owners in regards to the perceived benefits of dietary supplements or because of the greater difficulty in administering pills to cats, compared with dogs. Similar to the case for people, supplement use was more common for animals with disease in the present study than for animals that reportedly did not have any diseases.
There are a number of limitations to the present study. Disease prevalence was estimated on the basis of owner self-reporting. However, some pets could have had diseases that were not yet diagnosed. In addition, owners of other pets may have misunderstood the diagnosis made by their veterinarian or been reluctant to admit that their animal had a disease. Therefore, the reported prevalence may be lower than the true prevalence.
Similarly, there may have been underreporting by owners in regard to use of therapeutic diets and dietary supplements. Owing to the design of the survey, animals being fed a therapeutic diet were excluded from subsequent questions, including those regarding dietary supplements. Therefore, it is not known whether animals being fed therapeutic diets were also being given dietary supplements. Nonetheless, even if all 28 animals being fed therapeutic diets were also being given supplements, the proportion of animals receiving dietary supplements still would be lower than the proportion reported for people.
The present study also did not specifically compare urban and rural populations of animals, and this would be an interesting topic for future studies. Finally, there was a possibility for bias in the present study because those owners who were willing to participate in the survey may have been different from those who did not participate. Nonetheless, results of the present study suggest that most animals with diseases are not being fed therapeutic diets and that dietary supplement use appears to be less common in animals than in people. These results may be useful in designing nutritional studies, understanding where additional research is needed, and helping veterinarians to better communicate with pet owners about nutrition.
Survey available from the corresponding author on request.
SPSS, version 13.0, SPSS Inc, Chicago, Ill.
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