Influence of wet and dry commercial diets on the oral microbiota of Yorkshire terriers

Abstract

Background: Periodontal disease is common in dogs and is initiated by the build-up of plaque on the tooth surface. There is evidence that the feeding of dry diets may help prevent the build-up of plaque and calculus compared to softer wet diets. The primary objective of this study was to determine whether diet format influences the microbial composition of dental plaque.

Results: Subgingival (SG) and gingival margin (GM) plaque samples were collected from 28 Yorkshire terriers, housed within a research facility, between 37 and 53 weeks of age. Dogs were fed either wet commercial diets, dry commercial diets, or a simultaneous offering of the two. Illumina sequencing of the 16 S rRNA gene (variable regions 3 and 4) of 43 SG and 43 GM plaque samples resulted in the generation of 6,725,682 paired end reads. Exploratory factor analysis, a statistical method for dimensionality reduction of multivariate data, was used to identify groups of covarying bacterial species. Subsequent mixed effects modelling revealed significant differences in the scores of two of these groupings indicating systematic differences in prevalences of their component taxa. One grouping revealed that for GM plaque samples, the profile of bacterial species most descriptive of the wet diet was biased towards those associated with periodontal disease whereas for the dry diet it was biased towards those associated with healthy gingiva. The dogs fed a mixture of wet and dry diets had bacterial profiles in between the wet and dry diets, i.e. a mix of both health and disease associated taxa. The other bacterial grouping indicated that, in dogs fed a wet diet only, GM plaque was significantly associated with bacteria that preferred aerobic conditions whereas SG plaque was associated with taxa that favoured anaerobic conditions.

Conclusions: Although dry diets shifted the bacterial community towards a healthier profile compared to wet diets there was no evidence of improved periodontal health. Additional methods to maintain dental hygiene should therefore be promoted to ensure effective management of periodontal disease in dogs.

Keywords: Bacterial plaque; Canine; Dog; Microbiome; Oral; Periodontal disease.

Fig. 1

Non-metric multidimensional scaling dimensions 1 (Dim1) and 2 (Dim2) labelled by sample type (gingival margin plaque (crosshair) and subgingival plaque (filled circle)) and diet (wet (blue), dry (red) or mixture of the two (green)). Ellipses represent 95% bivariate data quantiles for each experimental group

Fig. 2

Boxplots of Shannon diversity for gingival margin and subgingival plaque samples when dogs were fed a dry commercial diet (red), wet commercial diet (blue) or a mixture of the two (green). Individual dots represent outliers

Fig. 3

Stacked bar chart showing the phylum level composition of gingival margin and subgingival plaque when dogs are fed wet commercial diets (wet), dry commercial diets (dry), and a mixture of the two (mixed)

Fig. 4

Boxplots of the scores for Factor Group 3 for gingival margin and subgingival plaque for each diet group: Commercial dry (red), commercial wet (blue), mixture of commercial wet and dry (green). Individual dots represent outliers

Fig. 5

Boxplots of the scores for Factor Group 7 for gingival margin and subgingival plaque for each diet type: Commercial dry (red), commercial wet (blue), mixture of commercial wet and dry (green). Individual dots represent outliers

Fig. 6

Schematic of the study design together with a summary of the number of dogs sampled and gingival margin and subgingival plaque samples collected at each timepoint