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Supplement: Waltham International Symposium

Age, Breed, Sex and Period Effects on Skin Biophysical Parameters for Dogs Fed Canned Dog Food

Friskies Product Technology Center, Nestec Limited, St. Joseph, MO

³To whom correspondence should be addressed. E-mail: linda.young{at}rdmo.nestle.com.

KEY WORDS: • dogs • skin • age • breed

EXPANDED ABSTRACT

Noninvasive skin biophysical methods have been used in clinical and experimental dermatology for humans (1). The application of some of these methods has also been investigated for companion animals (2–9). Skin biophysical measurements have been reported to be affected by age, breed, sex, site of measurement, animal excitement, evaluation (time) period or season, gonadal status and even coat color (9). The objective of this study was to look at the effect of age, breed, sex and time period on skin biophysical parameters for dogs fed a nutritionally complete and balanced canned food for adult dogs.

	MATERIALS AND METHODS

TOP MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
A total of 32 dogs with age range of 2 to 14 y were fed a nutritionally complete and balanced canned food for adult dogs for 8 wk. Of these dogs, 16 were Beagles, 8 were Fox Terriers, 4 were Labrador Retrievers and 4 were Manchester Terriers. Sixteen dogs were male, 16 were female. Dogs were fed to maintain their body weight. Skin thickness was measured using skin-fold calipers. Skin pH, sebum production rate and skin hydration were measured using Courage-Khazaka (Köln, Germany) Skin pH meter pH900, Sebumeter SM810 and Corneometer CM825. Skin transepidermal water loss (TEWL) was measured using Courage-Khazaka Tewameter TM210. Skin elasticity was measured using Courage-Khazaka Cutometer SEM575 using a 2-mm probe with 12-s suction, 3-s relaxation. The skin elasticity was calculated as the ratio between the immediate recovery and the immediate deformation after application of suction and removal of vacuum. About 24 h after shaving a small patch of coat on the right side of lumbar region, skin measures were made for each dog in the following order: skin hydration, sebum, skin elasticity, TEWL and skin pH. Measurements were made the wk before feeding the canned food, at 4 wk and at 8 wk. The protocol was approved by the Friskies Petcare Committee.

The purpose of the statistical analysis was to determine whether there were any differences between time period, breeds and sexes for any of the skin parameters and whether age was related to any of the skin parameters. The first part of the investigation was to do an analysis of covariance where age was included as a covariate. This was to determine whether age was related to any of the parameters. As part of this analysis, interactions between age and the other factors were examined. The data for all measurements (except for skin thickness) in the tables give the analysis of variance after the nonsignificant effects of age were eliminated. PROC MIXED in SAS was used to calculate the analysis of variance and covariance. Tukey’s multiple comparison procedure was used to determine differences between breeds and time periods. The correlation between age and skin thickness was calculated using Pearson’s correlation coefficient.

	RESULTS

TOP MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
There was a significant negative correlation (r = -0.47) between age and skin thickness. There were significant breed effects on skin thickness (P < 0.0001). Labrador Retrievers had thicker skin than that of the other breeds (Table 1). There was no significant effect of sex or time period on skin thickness.

There were significant differences in sebum values between breeds (P < 0.028) and time period (P < 0.0007) and there was a significant breed–period interaction (P < 0.018). Labrador Retrievers had higher sebum values than those of Beagles (Table 1). Beagles and Manchester Terriers did not show changes in sebum levels with time period, whereas Fox Terriers and Labrador Retrievers had decreased sebum values with time period.

For skin elasticity, there were significant differences between breeds (P < 0.0001). Manchester Terriers had lower skin elasticity compared to that of the other breeds (Table 1). There were no significant differences in skin elasticity resulting from age, sex or time period.

There were significant differences in TEWL values between breeds (P < 0.0001) and the difference between time periods was close to significance (P < 0.06). Beagles had significantly lower values for TEWL compared to those of Fox Terriers (Table 1). The TEWL values tended to decrease with time period (Table 2).

	DISCUSSION

TOP MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Scott et al. (9) reported dogs have an average skin thickness of 0.5 to 5 mm, with skin thickness decreasing dorsally to ventrally on the trunk and proximally to distally on the limbs. In humans, skin thickness was reported to vary because of sex, age and body site (10).

Skin hydration values for dogs were reported to vary by body site (6,8,9). Corneometer readings were reported to be reproducible at each body site tested by Beco and Fontaine (2) except for the concave ear pinna. Groux and Bensignor (8) were not able to obtain reproducible Corneometer readings from one day to the next. No differences in coat relative humidity were observed between males and females (9,11).

Skin pH has been reported to be affected by breed, sex, gonadal status, site of measurement, coat color, animal excitement, time period or season (5,9). No differences in skin pH were observed for dogs fed diets with (n-6):(n-3) fatty acid ratios ranging from 1:1 to 24:1 in a study by Campbell et al. (4).

Dunstan et al. (7) reported breed differences in sebum production rates, given that Labrador Retrievers and Siberian Huskies had higher sebum values than those of Miniature Poodles. Sebum values have been observed to vary from one day to the next (6) and to increase with time in puppies (7). There were no significant differences in sebum values that were associated with dietary treatment in the study of Campbell et al. (4).

Beco and Fontaine (2) and Groux and Bensignor (8) reported that TEWL values were not reproducible from day to day in individual dogs. Campbell et al. (5) did not observe significant seasonal differences for TEWL values. TEWL was significantly reduced in dogs with seborrhea sicca within 1 wk when sunflower oil was applied topically (3). Campbell et al. (4) did not observe differences in TEWL for healthy dogs as a result of dietary treatments. However, Marsh et al. (12) observed a significant decrease in TEWL values for Labrador Retrievers fed diets supplemented with high levels of zinc sulfate and safflower oil.

In conclusion, age, breed, sex and time period influenced various skin biophysical parameters of dogs in this study. For examination of dietary effects on skin biophysical parameters, it is recommended that studies be conducted with just one breed to minimize variability. Dietary effects should be examined with a concurrent control, given the potential for time period effects. It is also proposed that dietary treatment groups be balanced by age and sex.

	FOOTNOTES

 
¹ Presented as part of the Waltham International Symposium: Pet Nutrition Coming of Age held in Vancouver, Canada, August 6–7, 2001. This symposium and the publication of symposium proceedings were sponsored by the Waltham Centre for Pet Nutrition. Guest editors for this supplement were James G. Morris, University of California, Davis, Ivan H. Burger, consultant to Mars UK Limited, Carl L. Keen, University of California, Davis, and D’Ann Finley, University of California, Davis.

² Supported by Friskies Product Technology Center, Nestec Limited, St. Joseph, MO.

	LITERATURE CITED

TOP MATERIALS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 

1. Serup, J. & Jemec, G.B.E. (1994) Handbook of Non-Invasive Methods and the Skin 1994 CRC Press Boca Raton, FL .

2. Beco, L. & Fontaine, J. (2000) Corneometrie et perte d’eau transepidermique: validation des techniques chez les chiens. Ann. Med. Vet. 144:329-333.

3. Campbell, K. L. & Kirkwood, A. R. (1993) Effect of topical oils on transepidermal water loss in dogs with seborrhea sicca. Ihrke, P. J. Mason, I. S. White, S. D. eds. Advances in Veterinary Dermatology 2:157-162 Pergamon Press Oxford, UK .

4. Campbell, K. L., LaFlamme, D. P. & Harrison, J. (2000a) Effects of four diets with varying omega 6: omega 3 ratios on the health and appearance of the skin and hair coat in normal dogs. Vet. Dermatol. 11(suppl. 1):18(abs.).

5. Campbell, K. L., LaFlamme, D. P. & Harrison, J. (2000b) Seasonal variations in skin surface pH, skin surface hydration and hair epilation of normal dogs in Midwestern United States climate. Vet. Dermatol. 11(suppl. 1):19(abs.).

6. Chesney, C. J. (1995) Measurement of skin hydration in normal dogs and in dogs with atopy or a scaling dermatosis. J. Small Anim. Pract. 36:305-309.[Medline]

7. Dunstan, R. W., Herdt, T. H., Mei, L., Credille, K. M., Kennis, R. A., Maier, R. L., Dziezyc, J., Castle, S., Reinhart, G. A. & Davenport, G. M. (2000) The role of nutrition on canine sebum secretion: a preliminary report. Vet. Dermatol. 11(suppl. 1):2-3(abs.).

8. Groux, D. & Bensignor, E. (2000) Skin characteristics measured by trans-epidermal water loss, corneometry and sebometry are not valuable tools to evaluate the effects of topical treatments in dogs. Vet. Dermatol. 11(suppl. 1):60(abs.).

9. Scott, D. W., Miller, W. H. & Griffin, C. E. (2001) Muller and Kirk’s Small Animal Dermatology 6th ed. 2001 W.B. Saunders Co Philadelphia, PA .

10. Martin, A. D. (1994) Skin thickness: caliper measurement and typical values. Serup, J. Jemec, G.B.E. eds. Handbook of Non-Invasive Methods and the Skin 1994:293-296 CRC Press Boca Raton, FL .

11. Chesney, C. J. (1996) Mapping the canine skin: a study of coat relative humidity in Newfoundland dogs. Vet. Dermatol. 7:35-41.

12. Marsh, K. A., Ruedisueli, F. L., Coe, S. L. & Watson, T.D.G. (2000) Effects of zinc and linoleic acid supplementation on the skin and coat quality of dogs receiving a complete and balanced diet. Vet. Dermatol. 11:277-284.

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