History

Dog Gastrointestinal Sensitivity

Key Message

WALTHAM has contributed to the understanding of non-specific dietary sensitivity in dogs by:

  • Developing a robust system for grading faecal consistency.  
  • Defining a population of clinically healthy dogs that consistently produce poorer faeces quality; describing this population as having non-specific dietary sensitivity – they respond to dietary change, but it is not a response to specific dietary components or ingredients.
  • Characterising the physiological basis of non-specific dietary sensitivity; demonstrating that dogs with non-specific dietary sensitivity have a reduced capacity for absorbing water in the colon. Showing that altered colonic motility is not a significant factor in non-specific dietary sensitivity. Demonstrating that gastrointestinal inflammation is evident in the dogs with non-specific dietary sensitivity. Demonstrating that there are systemic effects of non-specific dietary sensitivity.
  • Showing that the susceptibility of German shepherds to chronic diarrhoea is not due to a failure of transcription of key genes encoding molecules involved in mucosal IgA secretion.

Background

Normal healthy dogs produce faeces within a range of consistency. Some individuals typically produce well-formed stools, no matter what they are fed. At the other end of the normal spectrum, some dogs intermittently produce looser or poorly-formed stools which respond to dietary changes (although it is not a response to specific dietary components or ingredients). WALTHAM has described these dogs as having non-specific dietary sensitivity. It has been estimated that around 10–15% of dogs worldwide are susceptible to gastrointestinal upset, especially when the diet is changed or certain diets are fed (Moxham 2001).

Dogs with non-specific dietary sensitivity are otherwise healthy on examination (Rolfe et al. 2002a). Their routine haematology and blood biochemistry values are within normal ranges and serum trypsin-like immunoreactivity and folate and cobalamin concentrations are normal.(Rolfe et al. 2002a) They also have no significant abnormalities in small intestinal absorptive function or permeability, as assessed using differential sugar absorption tests (Rolfe et al. 2000).

These findings suggest that the poor faecal consistency in dogs with non-specific dietary sensitivity might be caused by alterations in colonic motility, transport, or absorptive function. The efficiency of the large intestine for dehydrating the luminal contents is dependent on close coordination between colonic motility and absorptive functions (Rolfe 1999; Rolfe et al. 2002a).

Why WALTHAM is Interested

For any dog owner, loose faeces or diarrhoea can be a messy problem as well as a potential source of worry and concern. It is important to understand the underlying cause of loose faeces in dogs with non-specific dietary sensitivity in order to determine if a dietary solution might be found.

Approach

Describing faeces quality requires a robust and validated system to ensure reliability and reproducibility. WALTHAM developed a faeces scoring system, based on the appearance of the faeces.

Studies were conducted to investigate the gastrointestinal physiology of dogs with and without non-specific dietary sensitivity to understand the physiological basis of poor faeces quality.

Capability (Faeces Scoring)

To facilitate the reliable and reproducible description of faeces quality, WALTHAM developed a robust faeces scoring system.

The scoring system for faeces is based on its visual appearance (Moxham 2001). The scale runs from 1 to 5, with grade 1 representing ‘hard, dry, crumbly faeces’ and grade 5 representing ‘watery diarrhoea.’ To account for all the discernible points in between, half-scores are used, giving a total of 9 possible categories (Figure 1), with a score of 1.5–2.5 considered ideal.

Faeces Scoring System
Reproduced from Moxham G. The WALTHAM Faeces Scoring System - a tool for veterinarians and pet owners: how does your pet rate? Waltham Focus. 2001;11(2);24-25

Figure 1: The faeces scoring system in use at WALTHAM

At WALTHAM, this system has been in routine use for decades. Every day, faeces quality data are routinely collected for the hundreds of dogs and cats residing at the centre. Each defecation by every pet is individually scored and the data recorded. Many people at WALTHAM are involved in this process, and it is vital that the data are quantitative, consistent, accurate, and repeatable. To increase the robustness and reproducibility of the faeces scoring system, the WALTHAM team receives rigorous training and assessment and audits are regularly conducted.

The system is also in use in the community, providing a much-needed tool to help owners and veterinarians consistently describe faeces quality, and hence minimise misunderstandings that can delay diagnoses.
Based on a site wide survey of faeces quality, a panel of dogs with non-specific dietary sensitivity was formed at WALTHAM. When fed the same standard diet, they consistently produced faeces of poorer quality compared with the rest of the dogs.

Discovery (Water Absorption)

Dogs with non-specific dietary sensitivity have a reduced capacity for absorbing water in the colon

Disruption of colon electrolyte transport has been implicated in large-intestinal diarrhoea in other species. This study compared colonic function in dogs with non-specific dietary sensitivity with normal dogs (Rolfe et al. 2002a).

A panel of 12 dogs with non-specific dietary sensitivity and 9 normal (control) dogs were fed a series of diets for 4 weeks each in a crossover design (Rolfe et al. 2002a). The diets were selected because, from experience, they produced a range of faeces quality in the sensitive dogs. Faeces quality was recorded each day, and at the end of each diet period electrolyte and water transport were assessed, and colonic biopsy specimens obtained for histologic examination and measurement of crypt water uptake.

Colonic biopsy specimens were obtained by endoscopy, with crypt water uptake subsequently measured in vitro using a marker and confocal microscopy. Electrolyte and water transport were measured in vivo using small dialysis bags filled with a physiologic ionic solution that were placed in the lumen of the descending colon during endoscopy, and left for 30 minutes. After their removal (using a string attached to the base) water transport was determined by weight difference, and the concentration of electrolytes (sodium, potassium, bicarbonate, and chloride) was measured spectrophotometrically. This technique for measuring water and electrolyte transport was adapted from that used in humans.

In control dogs there was net colonic absorption of sodium and chloride and secretion of potassium and bicarbonate (Rolfe et al. 2002a). Electrolyte transport was disrupted in dogs with non-specific dietary sensitivity, with lower absorption of sodium and chloride compared with controls, particularly when fed diets that resulted in looser faeces (Rolfe et al. 2002a). Faecal consistency was inversely correlated with crypt water absorption, which was reduced in dogs with non-specific dietary sensitivity (Rolfe et al. 2002a). Colonic crypts were shorter and less dense in dogs with non-specific dietary sensitivity compared with control dogs (Figure 2), particularly when fed diets associated with poor faecal consistency (Rolfe et al. 2002a).

Good
© WALTHAM 2012

Poor
© WALTHAM 2012

Figure 2: Colonic physiology in a normal dog (A) and one with non-specific dietary sensitivity (B). The photomicrographs show shorter wider crypts in the sensitive dog

This study showed that dogs with non-specific dietary sensitivity are particularly sensitive to diet-induced changes in colonic absorptive function, which are associated with damage to colonic microstructure, disrupted electrolyte transport function, and impaired ability to absorb water from the lumen (Rolfe et al. 2002a).

Discovery (Colonic Motility)

Altered colonic motility is not a significant factor in non-specific dietary sensitivity

Gastrointestinal transit may be an important factor contributing to the ability to absorb water across the gastrointestinal tract, which if impaired may result in loose stools. This study investigated transit time in dogs with non-specific dietary sensitivity compared with normal dogs (Rolfe et al. 2002b).

Whole gut transit time (WGTT) was assessed in 12 dogs with non-specific dietary sensitivity and 8 normal (control) dogs which were fed 4 diets for 4 weeks each in a crossover design (Rolfe et al. 2002b). The diets were selected because, from experience, they produced a range of faeces quality in the sensitive dogs. Faeces quality was recorded each day, and WGTT measured during weeks 3 and 4 of each diet period using 30 plastic beads. The cylindrical plastic beads – each of which was 4 mm long and weighed 10 mg – were sprinkled on the food, and passed harmlessly through the gastrointestinal tract to be recovered in the faeces, the time of defecation being continuously monitored by video camera.

There was no significant effect of diet on mean WGTT within or between groups (Rolfe et al. 2002b). However, minimum WGTT (the time to the appearance of the first marker in faeces) was shorter in dogs with non-specific dietary sensitivity compared with controls, especially when fed diets producing poor quality faeces (Rolfe et al. 2002b). A shorter minimum WGTT was significantly associated with poorer faeces quality (Figure 3 Rolfe et al. 2002b).

Minimum WGTT graph
Reproduced from Rolfe VE, Adams CA, Butterwick RF, Batt RM. Relationship between faecal character and intestinal transit time in normal dogs and diet-sensitive dogs. J Small Anim Pract. 2002 Jul;43(7):290-294. Blackwell Publishing. The definitive version is available at http://onlinelibrary.wiley.com

Figure 3: A shorter minimum whole gut transit time (WGTT) is associated with poorer faeces quality (higher mean faeces score) (Rolfe et al. 2002b). Each point represents the mean results for one diet in one of the two groups of dogs (control and sensitive dogs)

This study suggests that altered colonic motility is not a significant factor, but that rapid transit of certain dietary components might contribute to loose faeces in dogs with non-specific dietary sensitivity (Rolfe et al. 2002b). Dogs with non-specific dietary sensitivity might be more sensitive to the effects of diet on minimum WGTT (Rolfe et al. 2002b).

Discovery (Inflammation)

Gastrointestinal inflammation is evident in the dogs with non-specific dietary sensitivity

In collaboration with researchers at the School of Veterinary Medicine in Hannover, Germany, and the University of Bristol, UK, WALTHAM investigated the morphology and immunopathology of the small and large intestine in dogs with non-specific dietary sensitivity (Zentek et al. 2002).

Endoscopic biopsies were taken from the small and large intestines of 10 dogs with non-specific dietary sensitivity and 8 normal (control) dogs that had been fed for 3 weeks on the same diet known to produce loose faeces in the sensitive dogs. The samples were stained and examined histologically, and cell surface markers investigated using immunohistochemistry and flow cytometry.

Compared with control dogs, those with non-specific dietary sensitivity exhibited (Zentek et al. 2002):

  •     A higher incidence of mild diffuse inflammation in the duodenum and colon (P<0.05).
  •     Higher percentages of CD45+ and CD4+ cells, and lower percentage of CD8+ cells, in the epithelium (P<0.05), with a greater CD4/CD8 ratio.
  •     Elevated numbers of colonic intraepithelial CD45+ and CD3+ lymphocytes (P<0.05).
  •     No difference in the cell populations of the colonic lamina propria.

This study showed that there are mild histological changes mainly in the colon of dogs with non-specific dietary sensitivity, associated with a tendency to higher numbers of intraepithelial lymphocytes and only minor changes in lamina propria cell populations (Zentek et al. 2002).

Insight Generation (Systemic Effects)

It is not only the gut that is affected in dogs with non-specific dietary sensitivity – there appear to be systemic effects

The haematology and blood biochemistry of 12 dogs with non-specific dietary sensitivity was compared with 10 normal dogs (Table 1 McNeill et al. 2001). The sensitive dogs had significantly reduced white blood cell counts (5.8 ± 0.8 x 109/L) compared with normal dogs (9.9 ± 3.9 x 109/L) due to reduced neutrophil and T cell populations (McNeill et al. 2001). No difference in C-reactive protein (CRP) levels was found (McNeill et al. 2001).

Table 1: Haematology and blood biochemistry of dogs with non-specific dietary sensitivity (McNeill et al. 2001)

Blood biochemistry of dogs
Image from the pre-peer reviewed version of McNeill L, Vallance CE, Boddy RY, Batt RM, Butterwick RF, Rolfe VE. Systemic changes during canine non-specific dietary sensitivity. J Vet Intern Med. 2001;15(3):312 [Abstract 163]which has been published in final form at http://onlinelibrary.wiley.com


This study suggests that compared with normal dogs, those with non-specific dietary sensitivity have systemic changes (McNeill et al. 2001).

Discovery (IgA Secretion)

The susceptibility of German shepherds to chronic diarrhoea is not due to a failure of transcription of key genes encoding molecules involved in mucosal IgA secretion

In collaboration with scientists at the University of Bristol, UK, WALTHAM investigated a potential cause of the susceptibility of German shepherd dogs to chronic diarrhoea (Peters et al. 2005).

Immunoglobulin (Ig) A plays an important role in gastrointestinal mucosal immune defence, and is present in mucosal secretions as a dimer, joined by the J-chain. The mucosal secretion of IgA relies on the polymeric immunoglobulin receptors (plgRs) for transport across the epithelia. A portion of the pIgR, termed the secretory component, remains bound to the dimeric IgA, and is an integral part of secretory IgA, increasing its resistance to proteases.

Decreased mucosal immunity associated with deficiency of serum IgA was implicated in small intestinal bacterial overgrowth in German shepherds (Batt et al. 1991), a condition that can result in chronic diarrhoea. Hence, decreased mucosal IgA secretion in German shepherd dogs might play a role in their apparent susceptibility to chronic diarrhoea.

This study used molecular techniques to examine the expression of mRNA transcripts for molecules involved in IgA secretion (plgR, alpha-chain, and J-chain) in duodenal biopsy specimens obtained endoscopically from dogs with and without chronic diarrhoea. A total of 39 dogs presenting with chronic diarrhoea (12 German shepherds and 27 dogs of other breeds) and 9 control dogs participated. No differences in the level of expression of any transcript were found among the different groups of dogs.

This study confirmed that the susceptibility of German shepherds to chronic diarrhoea is not a result of simple failure of transcription of the key genes that encode molecules involved in mucosal IgA secretion (Peters et al. 2005).

References

Batt RM, Barnes A, Rutgers HC, Carter SD. Relative IgA deficiency and small intestinal bacterial overgrowth in German shepherd dogs. Res Vet Sci. 1991 Jan;50(1):106-11.


McNeill L, Vallance CE, Boddy RY, Batt RM, Butterwick RF, Rolfe VE. Systemic changes during canine non-specific dietary sensitivity. J Vet Intern Med. 2001;15(3):312 [Abstract 163].


Moxham G. The Waltham feces scoring system - a tool for veterinarians and pet owners: How does your pet rate? WALTHAM Focus. 2001;11(2):24-25.


Peters IR, Helps CR, Calvert EL, Hall EJ, Day MJ. Measurement of messenger RNA encoding the alpha-chain, polymeric immunoglobulin receptor, and J-chain in duodenal mucosa from dogs with and without chronic diarrhea by use of quantitative real-time reverse transcription-polymerase chain reaction assays. Am J Vet Res. 2005 Jan;66(1):11-6.


Rolfe VE, Adams CA, Butterwick RE, Batt RM. Relationships between fecal consistency and colonic microstructure and absorptive function in dogs with and without nonspecific dietary sensitivity. Am J Vet Res. 2002a Apr;63(4):617-22.


Rolfe VE, Adams CA, Butterwick RF, Batt RM. Relationship between faecal character and intestinal transit time in normal dogs and diet-sensitive dogs. J Small Anim Pract. 2002b Jul;43(7):290-4.


Rolfe VE, Adams CA, Smith VV, Batt RM, Butterwick RF. Large intestinal abnormalities in canine non-specific dietary sensitivity. J Vet Intern Med. 2000;14:349 [Abstract 88].


Rolfe V. Colonic fluid and electrolyte transport in health and disease. Vet Clin North Am Small Anim Pract. 1999 Mar;29(2):577-88, viii.


Zentek J, Hall EJ, German A, Haverson K, Bailey M, Rolfe V, Butterwick R, Day MJ. Morphology and immunopathology of the small and large intestine in dogs with nonspecific dietary sensitivity. J Nutr. 2002 Jun;132(6 Suppl 2):1652S-4S.


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