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Eukanuba Skin and Coat Formula Effectiveness

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NUTRITIONAL MANAGEMENT OF CANINE ATOPY IN 47 DOGS:
A RETROSPECTIVE STUDY

Rod A.W. Rosychuk, DVM, DACVIM
Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, USA
Kathryn Scott-Fieseler, DVM
Veterinary Teaching Hospital, Colorado State University, Fort Collins, Colorado, USA
Stephen D. White, DVM, DACVD
Department of Veterinary Medicine and Epidemiology, School of Veterinary Medicine,
University of California, Davis, California, USA
Sarah Shackelford
Veterinary Teaching Hospital, Colorado State University, Fort Collins, Colorado, USA

ABSTRACT

A retrospective study of 47 dogs with atopy was conducted to assess the benefits of feeding Eukanuba Veterinary Diets® Nutritional Skin & Coat Formula™ Response FP®/Canine diet to manage atopy-related pruritus. Responses were judged as excellent (90-100%), good (50-89%), fair (25-49%), and poor (>25%). Excellent responses were noted in 5/47 (10.6%), good in 15/47 (32%), fair in 9/47 (19.1%), and poor in 18/47 (38.3%).

INTRODUCTION

Several studies have documented the efficacy of omega-3 and/or omega-6 fatty acids in the management of canine atopy.^1-6 Fatty acids have been used either alone or with other medications such as antihistamines for their synergistic effects in reducing pruritus ^7,8 or to reduce the concurrent dose of glucocorticoids required for pruritus control.⁹

In the skin, eicosanoids derived from the metabolism of cell membrane associated arachidonic acid (an omega-6 fatty acid) are noted to be potent mediators of inflammation and pruritus. They include 12-hydroxyeicosatetraenoic acid (12-HETE), prostaglandin E2, thromboxane A.², and leukotriene B4 (LBT4).¹⁰ The synthesis and release of these eicosanoids is noted to occur with Type I hypersensitivity reactions in atopy¹¹ and are related to mast cell degranulation, keratinocyte damage, and inflammatory cell infiltration.

Dietary supplements containing omega-3 fatty acids (eicosapentaenoic acid, docosahexaenoic acid) and certain omega-6 fatty acids (dihomo-g-linolenic acid, a metabolite of g-linolenic acid) are noted to be inserted into the membrane phospholipids of tissues with a corresponding decrease in concentrations of arachidonic acid. ¹² Omega-3 fatty acid metabolism produces eicosanoids such as leukotriene B5 (LBT5) and prostaglandin E3 (PGE3) which have either little or no inflammatory activity (eg, LBT5 is only 1/10 as potent as LTB4 in inducing neutrophil chemotaxis) or may inhibit the production of proinflammatory eicosanoids (eg, LTB5 inhibits production of LTB4). ¹⁰ Prostaglandin E1 (PGE1), an eicosanoid metabolite of dihomo-g-linolenic acid is antiinflammatory (eg, PGE1 inhibits the release of arachidonic acid). In that arachidonic acid, omega-3 fatty acids, and dihomo-g-linolenic acid compete for the same desaturase enzymes required, for their metabolism to various eicosanoids, dietary supplementation with omega-3 and certain other omega-6 fatty acids may competetively inhibit the metabolism of arachidonic acid, producing antiinflammatory or less inflammatory eicosanoids. ^10,12 The above would be expected to benefit the inflammation and pruritus associated with atopy.

Benefits of fatty acid supplementation in atopic dogs may also be related to the observation that some affected individuals appear to have abnormalities in fat absorption or clearance,13 and/or ?6-desaturase and/or 5-desaturase deficiencies. ⁶ 6-Desaturases are responsible for the production of g-linolenic acid and eicosapentaenoic acid from omega-6 and omega-3 precursors. In a deficiency state, this blockade in normal metabolism could result in the preferential production of proinflammatory eicosanoids. Supplementation with eicosapentaenoic acid (EPA) and g-linolenic acid (GLA) would be expected to minimize this effect and potentially benefit the atopic patient.

FATTY ACID SUPPLEMENTATION

In an open study of 58 dogs with atopic dermatitis, Miller et al. found an omega-6 and omega-3 combination dietary supplement (DVM Derm Caps® [DVM Pharmaceuticals, Inc., Miami, FL]; approximately 25 mg EPA, 13 mg a-linolenic acid, 10 mg GLA, and 545mg linoleic acid/9.1 kg body weight/d) to have an excellent response in reducing pruritus in 10/58 (17.2%) and a good response in 8/58 (13.8%) of atopic dogs. ²

There is some support for the hypothesis that much higher supplementation dosages of omega-3 fatty acids, approaching those used in controlling pruritus in human atopics, may provide better pruritus control in the dog. In one study, 3 of 5 atopic dogs had moderate to marked improvement in association with supplementing with 180 mg EPA and 120 mg of docosahexaenoic acid/4.55 kg body weight q 24 h.5 Numbers of dogs entered in the study were small and made interpretation of findings difficult.

More recently, emphasis has been placed on evaluating the effects of varying ratios of omega-6:omega-3 fatty acids in the diet. Vaughn et al. have shown that omega-6:omega-3 fatty acid ratios of 5:1 to 10:1 were associated with the production of lesser amounts of potentially pruritogenic leukotriene B4 when compared to omega-6:omega-3 ratios of 25:1, 50:1, and 100:1.12 A further potential benefit of feeding these fatty acids in a well-controlled, standardized commercial diet may be related to the observation that commercial diets differ, sometimes dramatically, in their fatty acid content. ¹⁴ The use of fixed-dose dietary supplements with diets of variable fatty acid content may significantly affect the total fatty acid intake and the final ratio of fatty acids consumed. This may help explain the wide variety of responses to essential fatty acid supplementation noted in various studies. ^1,2,4,5

RETROSPECTIVE STUDY

A retrospective study of 47 dogs with atopy was conducted at Colorado State University to assess the benefits of feeding the Eukanuba Veterinary Diets Nutritional Skin & Coat Formula Response FP/Canine diet (Response FP) in managing atopy-related pruritus. This diet has been supplemented with omega-3 fatty acids to achieve an omega-6:omega-3 ratio of approximately 5:1. The 47 dogs came from a group of 68 pruritic dogs who were fed the diet during the study time. A diagnosis of atopy was established based on signalment, history, physical findings, and if the pruritus was clearly seasonal. In these seasonally pruritic patients, flea bite hypersensitivity and seasonal infectious problems (bacterial pyoderma, Malassezia infections) were ruled out. In nonseasonally pruritic dogs, a diagnosis of atopy was based on signalment, history, physical findings, exclusion of ectoparasitism (fleas, scabies, cheyletiella), or infectious causes of pruritus (bacterial pyoderma, Malassezia), failure to benefit from at least an 8-week restrictive diet (but not the Response FP diet or a diet known to contain added omega-3 fatty acids), and the presence of significant numbers of intradermal skin test and/or in vitro serologic test positives for antigen specific IgE. Using these criteria, 21 dogs were excluded from the study. These 21 dogs were either atopic and food allergic or suspected or proven atopics for whom food sensitivity could not be ruled out as a contributor to the pruritus.

Response to the diet was based on both a retrospective evaluation of patients' records, along with a pet owner survey conducted by telephone and/or a written questionaire. Response was based on estimated percent reduction in pruritus. An excellent response was judged as 90-100% improvement, a good response was 50-89%, a fair response was 25-49%, and a poor response was >25%. Notation was also made of any worsening of pruritus while on the diet.

If patients were on other drug therapies, response to the diet was assessed based on subsequent reduction of drug dosages/frequencies required to manage pruritus. Association of response to the feeding of the diet was further assessed on the basis of worsening of pruritus following discontinuation of the diet.

Breeds affected included Golden Retrievers (9), Labrador Retrievers (9), Cocker Spaniels (4), Doberman Pinschers (2), Dalmatians (2), German Shepherd Dogs (2), West Highland White Terriers (2), Newfoundlands (2) and one each of the following: Fox Terrier, Miniature Schnauzer, Jack Russell Terrier, Lhasa Apso, Corgi, Basset Hound, Australian Shepherd Dog, Collie, and English Bulldog. Five mixed-breed dogs were also included.

The diet was fed for an average of 17.7 months.

RESULTS

Excellent responses were noted in 5/47 (10.6%), good responses in 15/47 (32%), fair responses in 9/47 (19.1%), and poor responses in 18/47 (38.3%) (Figure). One dog was considered to be more pruritic when on the diet. In summary, good to excellent responses (>50% improvement) were noted in 42.6% of cases.

Results of this retrospective study are similar to those of Scott and Miller et al. who performed an 8-week dietary trial in 18 atopic dogs with a commercial lamb and rice dog food containing an omega-6:omega-3 fatty acid ratio of 5.5:1. Six of the 18 (33%) had an excellent response to the diet and 2 of 18 (11%) had a good response during the initial 8-week feeding period. Reduction in pruritus was appreciated within 7 to 21 days of the initiation of the test diet. When these 8 dogs were returned to their previous diet, pruritus returned within 3 to 14 days. Reinstitution of the test diet again resulted in good or excellent reduction of the pruritus. Interestingly, 7/11 (65%) failed to be benefited by more routine fatty acid supplements. ⁶

Schick et al assessed the efficacy of the diet in 31 dogs with either confirmed atopy, adverse reactions to foods, or a combination of both. The diet was fed for 8 weeks. Fourteen of 31 (45%) were judged to have good to excellent responses to this dietary change. Specific numbers of dogs who were only atopic within this group were not given. ¹⁵

Our retrospective study has flaws that likely did influence our results. The placebo effect of feeding a diet that was generally given free to the owners was likely significant. This statement was supported by the fact that only 13 of 28 owners of atopic dogs in the fair to excellent response groups elected to continue to buy the diet once they were no longer provided with the free product. Those who stopped using the diet cited the cost and inconvenience of obtaining the product as reasons for discontinuation.

Subjective impressions of response could have also been influenced by seasonal changes, although 29/47 cases were monitored for at least 12 months while on the diet. Nineteen of the 29 were monitored for at least 24 months.

Dogs were also maintained on other medications, including hyposensitization during the feeding of the diet. Benefits from hyposensitization, which may be highly unpredictable with respect to time of onset, could have influenced these results.

It could also be argued that lack of response to a given restrictive diet (especially if commercially prepared) does not rule out the possibility of food sensitivity and that some of the dogs may indeed have had some degree of food sensitivity and may have benefited from the restrictive nature of the fish and potato diet.

Other factors may have actually reduced the incidence or degree of reported benefits of the diet. Three dogs were only kept on the diet for 2 months. All 3 dogs had poor responses to the diet. Although there are several reports of rapid responses to fatty acid supplementation (decreases in pruritus within the first 7 days of supplementation) it is also noted that supplementation periods of 9 weeks were required to detect significant changes in the levels of arachidonic acid in the skin of dogs.10 In these 3 dogs, the diet trial may have benefited from being longer. We also limited our evaluation to pruritus. It is conceivable that other parameters of inflammation (ie, erythema, edema, alopecia, coat condition) may have more significantly improved in association with the diet.

SUMMARY

The Response FP diet does appear to benefit the pruritus associated with canine atopy in a significant number of dogs. It should be considered part of the therapeutic armamentarium used in managing atopy in the dog.This article was originally published in Recent Advances in Canine and Feline Nutrition, Vol. III: 2000 Iams Nutrition Symposium Proceedings. Wilmington, OH: Orange Frazer Press, 2000.

Eukanuba Veterinary Diets, Response, and Response FP are registered trademarks of The Iams Company. Nutritional Skin & Coat Formula is a trademark of The Iams Company.



 

REFERENCES

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