Royal Canin Nutritional Information

5. Nutritional Information

Focus on: Nutrients Acting on Oral Health in Cats

Servet E., Hendriks W., Clarke D., Biourge V. - Royal Canin Research Center, Aimargues, France - Massey University, New Zealand

Introduction

It has been shown that diets consisting of dry, hard foods result in less accumulation of plaque and tartar compared to canned or other soft foods. This is due to the abrasive nature of the dry food which can scrape or brush the accumulated materials off the tooth surface. In addition, the shape of the kibble has an important role in efficacy of brushing the tooth (when the owner cannot perform tooth brushing of the cat on a regular basis). A previous study (Servet et al, 2003) has reported that in cats, a rectangular kibble is more effective in preventing plaque than a triangular kibble.

The purpose of this study was to determine if chelated polyphosphates (sodium polyphosphate- SPP), a unique plaque reducing nutrient (PRN) and a larger kibble size would result in a significant reduction in calculus and plaque formation. SPP is a cation sequestrant that forms soluble complexes with calcium within dental plaque, thereby preventing the accumulation of calculus. A larger kibble of a rectangular shape should require additional prehension, biting and chewing to impact calculus and plaque formation.

Materials and Methods

Animals

A total of 30 healthy mixed breed cats were used in the study. To be included in this study, cats had to have normal dentition, scissor-configuration occlusion, dental plaque accumulation and no or mild gingivitis. Cats were housed in groups of 10 and provided their respective diet ad libitum. Fresh water was also provided ad libitum.

Diets

Cats were exclusively fed dry extruded diets throughout the study. No snacks, calculus or plaque control treats, chews or chew toys were allowed. Three different dietary regimens were compared:

- Diet A: A dry-expanded diet with triangular kibble shape and no oral care purpose, as a negative control diet
- Diet B: A dry-expanded diet with rectangular kibble shape formulated for oral care purpose, including SPP and PRN
- Diet C: A dry-expanded diet with triangular kibble shape and oral care provided by SPP.

All diets were formulated to meet the nutritional levels established by the AAFCO Cat Food Nutrient Profiles for adult maintenance.

Study Design

All 30 cats were fed Diet A for 14 days in a pre-study phase (Table 1). At the end of the pre-study phase, all cats were anesthetized and a dental prophylaxis performed to remove all supra and subgingival calculus and plaque. Each cat was deemed to begin the study with a "clean tooth model". All cats remained on Diet A and after a further seven days, plaque indexes were evaluated according to the Logan & Boyce procedure (Logan & Boyce, 1994). Cats were then randomly assigned by gender and plaque forming ability to one of 3 diets. Plaque indexes were evaluated at 7 days. At 28 days, plaque and calculus indexes were evaluated by the Logan & Boyce (plaque) and Warrick & Gorrel (calculus) procedures (Warrick & Gorrel, 1995). Calculus formation was evaluated a second time at day 56 (Table 2). One scorer was used to score all cats in a blinded procedure to the different feeding regimens and the scoring order of the cats.

The scored teeth were the canines (C), pre-molar 3 and 4 (PM3 and PM 4) for the upper jaw (maxilla) and C, PM3, PM 4, and molar 1 (M1) for the lower jaw (mandible).

Gingivitis was evaluated according to the method of Loe & Silness. Teeth scored were incisor 3 (I3), C, PM3, PM4, M1 for the maxilla and C, PM2, PM3, M4, M1 for the mandible.

Table 1 . Study design.

Data Analysis

Dental plaque and calculus scores were expressed as a whole mouth score for each cat and were calculated from the mean value of the scores for each target tooth. Data were expressed as mean ± standard error of the mean (sem). Repeatedmeasures ANOVA tests were used to derive F-tests for significant differences between treatments. F-values with p-values less than 0.05 were considered significant. Analyses were performed using the General Linear Model procedures in Statgraphics V5 statistical software.

Results

Plaque score at day 7 (Figure 1) was significantly lower for Diet B compared to Diet A and Diet B compared with Diet C (28.3% and 28.1%, respectively). In addition, gingival plaque score at Day 7 (Figure 2) was significantly lower for Diet B compared with Diet A and Diet C (27.3% and 30.5%, respectively). Diet B was associated with a 30.3% lower plaque score at day 28 compared to Diet A, and 30.1% lower plaque score at day 28 compared to Diet C (Figure 3). Likewise, Diet B was associated with a significant reduction in gingival plaque scores at day 28 (Figure 4) compared to both Diet A and Diet C (31.7% and 29.2%, respectively).

Figure 1. Plaque score day 7.

Figure 2. Gingival plaque score day 7.

Figure 3. Plaque score day 28.

Figure 4. Gingival plaque score day 28.

Calculus score at day 28 (Figure 5) was significantly lower for Diet B compared to Diet A and Diet B compared with Diet C (47.4% and 23.8%, respectively). In addition, there was a significant reduction (30.9%) in calculus score for Diet C compared with Diet A. The calculus score (Figure 6) for Diet B was significantly lower than Diet A or Diet C at 56 days (44.6% and 18.9%, respectively). The calculus score for Diet C was significantly lower (31.7%) than Diet A at 56 days.

Figure 5. Calculus score day 28.

Figure 6. Calculus score day 56.

Discussion

The results of this study demonstrated that plaque and calculus accumulation can be significantly reduced in cats when they are fed a diet that has been specifically formulated with a larger rectangular kibble coated with sodium polyphosphate and a specific plaque reducing nutrient. Plaque was reduced by approximately 30% and calculus was reduced by approximately 45%.

Coating the kibble with sodium polyphosphate alone (Diet C) resulted in significantly less calculus build up compared to the control diet (Diet A), but no significant reduction in plaque was observed. These results confirm that sodium polyphosphate has a significant impact only on calculus, and the results are in agreement with other available feline calculus data (Stookey,1995; Johnson & Cox, 2002).

Sodium polyphosphate, coated on the external surface of the kibble is released into the oral cavity where it chelates salivary calcium so that it is unavailable for plaque calcification into calculus. When swallowed, the calcium polyphosphate complexes are not stable in the acid environment of the stomach and are rapidly converted to orthophosphates and used as a dietary phosphate source.

The larger, rectangular kibble coated with sodium polyphosphate resulted in significantly less calculus accumulation compared to the smaller triangular kibble coated with sodium polyphosphate (Diet C). Previous studies have shown that diet texture, kibble shape, size and design all impact calculus formation in cats (Servet et al, 2003). Indeed, it has been shown that dry kibble in a rectangular shape as opposed to a triangular shape aids in scraping away plaque when the cat bites and chews the kibble (Servet et al, 2003). This lower plaque deposition rate is attributed to the specially designed kibbles that convey an enhanced mechanical action, attributed to increased friction, induced both a higher crunching rate and by optimized crushing with greater teeth penetration into the kibbles. This process mimics tooth brushing. The significant impact on plaque deposition was attributed to the addition of the unique plaque reducing nutrient, coupled with the size, shape and texture of the kibble, which enhanced the mechanical action and simulated a brushing effect.

Conclusion

A 30% reduction in plaque and 45% reduction in calculus accumulation can be achieved when cats are fed a diet that has been specifically formulated with a larger rectangular kibble coated with sodium polyphosphate and a specific plaque reducing nutrient.

Key Points to Remember: Periodontal Disease in Cats

70% of cats aged over 3 years old present oral lesions (Harvey, 2004). © Yves Lanceau/Royal Canin (British Shorthair).

Periodontal disease is the most common disease, affecting 70% of cats aged 20-27 months to various degrees (Ingham et al, 2002). It develops in three phases:
- Phase 1: deposition of dental plaque, constituting an organic film of salivary polysaccharides and glycoproteins, colonized by aerobic bacteria;
- Phase 2: development of gingivitis and mineralization of the dental plaque into calculus. The aerobic bacteria are replaced by anaerobic bacteria and bad breath is caused by the formation of volatile sulfur compounds;
- Phase 3: destruction of the periodontal ligament (periodontitis). The bacteria reach the base of the root and attack the bone in which the tooth is embedded. Gum recession and osteolysis facilitate the tooth’s loosening.

Figure 7. Dental follow up.

Nutritional Responses

Tooth brushing is the best means of preventing the development of periodontal disease. When it is not possible because the owner is not available or the cat is uncooperative, the food can play a beneficial preventive role based on its mechanical and/or chemical effects. The expected benefits are observed only when the cat eats nothing else on a daily basis.

Mechanical Effect

Dry foods can have a light abrasive effect on the teeth when they are chewed correctly before swallowing. This permits the destruction of the bacterial mesh that constitutes dental plaque. It is important not to crush or mash the kibbles, as this will negate these benefits.

The mechanical effect is based on matching the appropriate kibble size, shape and texture to the age and size of the individual animal. The aim is maximum penetration of the kibble by the tooth before the kibble crumbles, so as to obtain relative "brushing".

The fact that the cat chews also stimulates the production of saliva, which has a beneficial antibacterial role.

Effect on Bacterial Flora

Some nutrients can inhibit the deposition of dental plaque by curbing the adhesion of bacteria and/or acting as a bactericide (Servet et al, 2006). The aim is to reduce the proliferation of the anaerobic bacterial population and the production of volatile sulfur compounds responsible for halitosis.

While no specific studies have been published on cats, several studies have demonstrated the efficacy of some nutrients in limiting bad breath. Of the nutrients studied, organic zinc salts (e.g., zinc citrate) and inorganic zinc salts (e.g., zinc sulfate: ZnSO4 2-) present beneficial bacteriostatic properties (Weesner, 2003; Waller, 1997).

There are also bacteriostatic and bactericidal oils. Eucalyptus oil for example helps actively reduce the production of sulfur fatty acids (Pan et al, 2000). Lastly, some bacteria are highly sensitive to the action of tea polyphenols (Isogai et al, 1995), the antioxidant properties of which are well known.

Chemical Effect

Sodium polyphosphates have a chelator effect on the calcium in saliva and so help limit the calcification of dental plaque.

Conclusion

Adding up the impact of size/texture and composition of daily food, it is now also possible to promise a significant reduction in the deposition of dental plaque in cats.

Nutritional Information References

Harvey CE. The oral cavity. In: Chandler EA, Gaskell CJ, Gaskell RM; Feline medicine and therapeutics 2004; Blackwell Publishing & BSAVA: 379-395.

Ingham KE, Gorrel C, Blackburn JM, et al. The effect of tooth brushing on periodontal disease in cats. J Nutr 2002; 132: 1740S- 1741S.

Isogai E, Isogai H, Kimura K, et al. Effect of Japanese green tea extract on canine periodontal diseases. Microbial Ecology in Health & Diseases 1995; 8: 57-61.

Pan P, Barnett ML, Coelho J, et al. Determination of the in situ bactericidal activity of an essential oil mouth rinse using a vital stain method. J Clin Periodontol 2000; 27: 256-261.

Servet E, Hendriks W, Clarke D, et al. Dietary intervention can improve oral health in cats. J Vet Dent 2008 (in press).

Waler SM. The effect of some metal ions on volatile sulphur-containing compounds originating from the oral cavity. Acta Ondontol Scand 1997; 55: 261-4.

Weesner BW Jr. Curing Halitosis: the sweet smell of success. J Tenn Dent Assoc 2003; 83: 20.