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Are Dogs Fed a Kibble-Based Diet More Likely to
Experience an Episode of Gastric Dilatation Volvulus
Than Dogs Fed an Alternative Diet?
A Knowledge Summary by
Louise Anne Buckley PhD, RVN 1*
1 Harper Adams University, Newport, Shropshire, TF10 8NB
* Corresponding Author (lbuckley@harper-adams.ac.uk)
ISSN:
2396-9776
Published:
19 Apr 2017
in:
Vol 2, Issue 2
DOI:
http://dx.doi.org/10.18849/ve.v2i2.63
Reviewed by:
Nicola Ackerman (BSc(Hons), RVN, CertSAN,
CertVNECC, VTS(Nutr), A1 V1 MBVNA) and Sue
Badger (MEd, Cert Ed, RVN)
Next Review Date:
19 Apr 2019
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KNOWLEDGE SUMMARY
Question
Are dogs fed a kibble-based diet more likely to experience an episode of gastric dilatation volvulus than dogs
fed an alternative diet?
Clinical Scenario
A client attends the veterinary clinic with a breed of dog considered to be at a high risk of gastric-dilatation
volvulus (GDV). During the consultation, the dog’s dietary needs are being discussed. The client says that they
have been on an internet discussion forum and other owners have warned them that feeding a dried, kibble-
based diet will put their dog at an increased risk of having an episode of GDV. The client asks you, the
veterinary practitioner, what the evidence is for this claim.
The Evidence
The literature searches uncovered six papers (Glickman et al., 1997; Elwood, 1998; Theyse et al., 1998;
Raghavan et al., 2004; Pipan et al. 2012; Uhrikova et al., 2015) that either partially or fully addressed the PICO
question. These papers do not neatly address the PICO as the dogs studied either all/almost all were fed a
kibble only diet or kibble as the primary diet (Glickman et al., 1997; Ragavan et al., 2004) or fed different diet
types in combination (Theyse et al, 1998; Uhrikova et al., 2015) and/or assessed diet in terms of the
maximum size of the food particles (Theyse et al, 1998; Uhrikova et al., 2015) that comprised the diet fed so
the summaries of the experimental details should be examined for further understanding.
Of these papers, one paper found feeding a kibble diet increased GDV risk (Pipan et al., 2012) but failed to
match dogs for size between groups so the findings may have been biased if large breed dogs are more likely
to be fed kibble-based diets. One paper (Uhrikova et al., 2015) found no effect of feeding a kibble only diet,
but dogs fed a diet containing some kibble were more likely to experience a GDV than dogs fed a diet with no
kibble. However, in this study the median weight of the dogs in the control group was significantly different
to those in the two GDV groups (groups based on GDV – survival: 1. Survived, 2. Died) making this study
susceptible to the same criticism leveled at Pipan et al. (2012). However, the direction of effect is not
reported (i.e. it is not clear whether the dogs in the control group were lighter or heavier than one or both of
the GDV groups). Raghavan et al. (1997) claimed there was no effect of feeding a kibble diet but all, bar two,
dogs (n = 318) in their study were being primarily fed a dry, kibble-based diet so there was no alternative diet
control group to compare to and thus the effect of feeding kibble not amenable to meaningful statistical
analysis. In Elwood (1998), the main statistical analysis demonstrated no effect of kibble on GDV risk, but the
initial analysis did identify kibble as a potential risk factor. However, feeding a diet that contained no kibble
Clinical bottom line
Most of the studies that attempt to either partially or fully address the PICO contain limitations that mean
that they should either be rejected as unable to address the PICO or viewed with caution due to potential
bias in the population studied. Of the two studies that remain, the findings conflict. One study found dogs fed
a diet containing small particles only (<5mm, mainly dry kibble fed dogs) at greater risk of GDV than those fed
a diet containing large particles (>30mm, at least partly non-kibble based). The other study found no
significant effect of kibble on GDV risk once other potential risk factors were controlled for in the analysis.
Consequently, there is insufficient quality evidence to support the claim that feeding a kibble diet is
associated with an increased risk of GDV. However, it is worth noting that no studies found that dogs fed a
diet that contained no kibble (dry or moistened) were at increased risk of GDV, and the addition of either
table scraps, canned food or non-kibble supplements to the dog’s diet reduced the risk in some studies but
more research is needed to unpack the implications of this for feeding a kibble diet.
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reduced the risk of GDV (Uhrikova et al., 2015), as did feeding table scraps (but not canned commercial food)
as part of the diet (Glickman et al., 1997) or adding fish or egg supplements to the diet (Pipan et al., 2012).
Several studies (Glickman et al., 1997; Elwood, 1998; Raghavan et al., 2004; Uhrikova et al., 2015) reported
collecting data on dry and moistened kibble diets, but only one paper (Glickman et al., 1997) reported their
findings specifically in relation to dry kibble versus moistened kibble. They found that moistening the dry
kibble diet before feeding did not affect risk of GDV compared with feeding dry kibble only.
Both of the papers (Theyse et al., 1998; Uhrikova et al., 2015) that focused on particle size present within the
diet found that feeding a diet with small particles of food only (< 5mm; Theyse et al., 1998) or medium
particles of food as a maximum (5-30mm, but not small particles less than < 5mm; Uhrikova et al., 2015)
increased risk of GDV compared with dogs fed a diet containing some large particles of food (> 30mm). In
these studies, any diet containing particles greater than > 30mm contained none-kibble components (either
partially or exclusively). In the Theyse et al. (1998) study, 83% (19/23 dogs) in the < 5mm category were fed a
kibble only diet. No studies identified feeding a diet that did not contain kibble as a risk factor for GDV.
Summary of the evidence
1. Pipan (2012)
Population:
Privately owned dogs (any breed or mix, both sexes, neutered and
entire) across a wide geographic area.
The survey was potentially available to English speaking dog owners
with access to the internet in any country worldwide.
Sample size:
2551 surveys included in the analysis:
Control group (dogs without a GDV): 1437 respondents
Gastric dilatation-volvulus group (GDV): 1114 respondents
Intervention details:
Online survey based study, with ad hoc convenience sampling of dog
owners.
The questionnaire was divided into three sections:
1. Demographic information (year of birth, breed, sex, neuter
status, and purpose of the dog; country and postcode of
respondent). Whether the dog had ever had a GDV that
required surgical intervention. This latter question was used
to divide dogs into the control group and the GDV group.
However, the authors then also included within the GDV
group dogs that did not have surgery, or died / were
euthanised without surgery but were considered to have a
GDV (whether confirmed or presumed).
2. GDV group: a series of 44 questions divided into 4 categories
were asked that covered:
i. Dog specific factors
ii. Management factors
iii. Environmental factors
iv. Personality factors
3. Control group: The same questions were asked of the
control group dog owners as were asked of the GDV group,
with the exception that they were not asked any questions
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about the GDV episode (as the dogs had not experienced a
GDV). They were asked one additional question (had the dog
had a prophylactic gastroplexy?). These changes reduced the
total number of questions asked to 32.
Study design:
Cross-sectional study
Outcome studied:
The outcome measure was a GDV episode that required surgical
intervention in the dog’s history. The study looked for factors that
were associated with an increased incidence of GDV in the
population studied.
Of relevance to this PICO, the authors’ asked owners:
1. What type of diet the dog was fed? (dry kibble, canned food,
raw commercial, cooked homemade, raw homemade)
2. Whether the dog’s diet was supplemented with any of the
following? (eggs, cod liver oil, fish, cooked chicken, raw
chicken, cottage cheese, yoghurt*)
*plus others not clearly relevant to changing the diet texture or
moisture content.
Main findings:
(relevant to PICO question):
The primary relevant finding was that feeding a kibble diet
significantly increased the risk of GDV (Odds ratio: 1.7, 95%
confidence interval: 1.21 – 2.39, P = 0.002).
Adding the following supplements to the dog’s diet significantly
reduced the risk of GDV:
- Fish dietary supplements (Odds ratio: 0.51, 95% confidence
interval: 0.37 – 0.70, P < 0.001)
- Egg dietary supplements (Odds ratio: 0.57, 95% confidence
interval: 0.44 – 0.73, P < 0.001)
Feeding table scraps had no effect on GDV risk. The authors mention
this finding in the discussion and there is no statistical output
reported.
Limitations:
The incidents of GDV were retrospective so owners may have
already altered their dog’s diet (either type or by the addition of
supplements), on the basis of veterinary recommendation or lay
research. The authors do not outline whether owners were asked to
complete the form based on the dog’s diet at the time (or
preceding) the GDV, or, the present time, or not given a time frame
to use.
The study recruited dogs of any size, breed, and age. There was no
attempt to match control and GDV cases across other dimensions
that may have been relevant (e.g. breed, size, and/or age) in the
study design or analysis and this may have affected the results. For
example, are owners of large or giant breed dogs more likely to feed
a dry kibble diet than owners of small and medium sized dogs (e.g.
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for reasons of economy)? And, if so, is any significant effect of kibble
real or an artefact of the fact that large and giant breed dogs are
more likely to have a GDV than small breed dogs? This would
potentially skew the data in the direction reported by the authors.
This failure to match control and GDV cases across other potentially
relevant dimensions is one of the biggest drawbacks of this study
and it would have been more useful if the study authors had
restricted the study only to at risk breeds and / or dogs over a
certain size (large / giant breeds) when answering this research
question.
The authors do not report investigating interactions between diet
type and supplements in terms of increased or decreased risk. E.g.
did adding fish to the diet of kibble fed dogs reduce the risk of GDV,
but have no effect on the risk of GDV of canned fed dogs? Etc. This
limits the ability of the reviewer to interpret the supplement findings
in relation to the PICO or develop hypotheses to explain the study’s
primary diet type finding.
2. Theyse (1998)
Population:
Great Danes.
Sample size:
109 dogs:
- 38 dogs that had presented at the authors’ vet clinic with a
GDV
- 71 dogs owned by members of a Great Dane breed society
Intervention details:
Clinic records were retrospectively searched for cases of acute GDV
in Great Danes presented to the clinic over a 14 year period (January
1981 – December 1994). No information is provided on the fate
(survived or died) of the dogs that attended the clinic.
Control dogs were obtained by contacting a Great Dane breed
society.
Owners of both groups of Great Danes were asked to complete a
questionnaire that asked owners about their feeding and exercise
regime.
Demographic information was also recorded (age, sex, neuter status;
and, for GDV dogs only, type of food eaten before the GDV episode).
Of particular relevance to this PICO, owners were asked about their
dogs’ diet and asked to provide a sample of the diet fed to their dog.
Study design:
A cross sectional study (based on the RCVS Knowledge Knowledge
Summary guide); the authors’ describe it as a case-control study.
Outcome studied:
The outcome of interest was whether the dogs had had an episode
of GDV. The authors were then interested in identifying risk factors
that were associated with a GDV outcome.
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Of relevance to this PICO, the authors’ asked about the dog’s diet
and requested to provide a sample of the diet they fed their dog. All
owners in the study complied (n=109). Because the diet fed was
often a combination of commercial brand(s) and/or home –
prepared food and meat, the authors altered the risk factor/variable
studied to maximum food particle size within the sample ration
provided.
An ordinal scale was used:
1. <5mm (kibble or kibble and ground home-prepared food)
2. 5-30mm (dry dog food and/or canned dog food and/or
small, cut up pieces of home-prepared food). The dry dog
food was a mix of meat chunks, flakes and grains.
3. > 30mm (commercial dog food and/or home-prepared food,
plus large chunks of meat). The commercial dog food was
either kibble, dry, or canned dog food.
Main findings:
(relevant to PICO question):
Dogs fed a diet that contained some particles that were greater than
30mm were 75% less likely to have a GDV episode than dogs fed a
diet in which the maximum particle size was <5mm (Odds ratio: -
0.25, P = 0.017).
A significant difference in risk of GDV was not observed between
dogs in the <5mm category and dogs in the 5-30mm category. No
further output is provided here.
Eighty three percent (19/23) dogs in the <5mm category were fed a
dry kibble diet only.
Limitations:
The authors retrospectively searched clinic records for GDV cases in
Great Danes between 1981 and 1994 and owners of affected dogs
were contacted to complete a questionnaire that retrospectively
assessed feeding and exercise regime and to provide a diet sample.
- Thus, owners were often being asked to recall information
about their dog’s exercise and diet regime many years (up to
circa 13 years if they conducted their retrospective search in
1994/5) after the GDV episode and/or likely death of their
dog. Factual recall is likely to be poor under these
circumstances and this will have implications for accuracy of
both diet type recall and sample provision. Whereas, control
group owners were probably being asked about an existing,
current dog that they own (not enough information is
provided to say this for certain).
- Alternatively, dietary and exercise regime modifications may
have been implemented post-acute GDV episode (in the
dogs that survived) and these reported by the owner as their
regime. This would prevent accurate measurement of risk
factors associated with GDV development. There is not
enough detail provided by the authors to allow this
possibility to be evaluated.
- There is not enough information provided regarding the way
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that the owners fed their dogs the diet type. For example,
does dry kibble diet refer to the type of food or the way in
which the dry kibble diet was fed (e.g. was it fed ‘dry’ or fed
‘soaked’?). If the kibble diet was fed soaked by the owners,
did the researchers soak the kibble before measuring the
particle size? Was this information extracted from owners?
3. Glickman (1997)
Population:
Owned dogs within the USA.
Sample size:
202 dogs (101 matched case-control pairings).
Intervention details:
Several veterinary practices were contacted to complete a clinical
data sheet for dogs that were presented at the clinic, diagnosed with
GDV, and whose owners were willing to be contacted by
researchers. Vets were asked to also identify a similar dog (matched
for age and breed if pure breed, or age and weight if cross bred).
Researchers provided their own case control dog through the
university veterinary hospital if vets were unable to.
All owners (GDV, and case-matched control) were interviewed by
phone. Data on the following areas were collected:
- The owner of the animal
- Environmental factors
- Clinical history
- Physical activities
- Dietary factors
- Personality and temperament
Two types of questions were asked:
1. Those designed to evaluate the dog in the 8 hours preceding
the GDV episode (GDV dogs) or telephone interview (case-
dogs)
2. Those designed to evaluate the dog’s behavior, diet, etc
more generally over the preceding year.
Of particular importance to this PICO was diet and nutrition. The
authors do not set out within the methodology what type of data
they collected in respect of this. From the results section, it is
possible to identify that the owners were asked about:
- Diet type (dry, canned)
- Use of dietary supplements
- Whether the dry food was moistened
Study design:
A cross sectional study (based on the RCVS Knowledge Knowledge
Summary guide); the authors’ describe it as a case-control study.
Outcome studied:
The outcome variable was an episode of GDV. The authors looked
for risk factors associated with this. Of relevance to this PICO, the
potential risk factor evaluated included:
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- Diet type (canned, dry)
Of possible relevance to this PICO, the following additional potential
risk factors were evaluated:
- Use of dietary supplements
- Whether the dry diet was moistened or not
- Feeding of table scraps
Main findings:
(relevant to PICO question):
Almost all of the dogs, irrespective of GDV development, were fed a
dry diet on a regular basis so the authors concluded that it was not
possible to evaluate dry diet as a risk factor.
Feeding canned dog food did not significantly affect risk of GDV
(odds ratio: 0.72, 95% confidence interval: 0.32 – 1.42, P = 0.34)*.
Feeding table scraps significantly decreased the risk of GDV (odds
ratio: 0.41, 95% confidence interval: 0.17 – 0.96, P = 0.04)*.
Moistening the dry dog food did not affect risk of developing a GDV
(p >0.25, no other values reported).
Very few dogs in either group were fed supplements, so the authors
concluded that it was not possible to evaluate supplement use as a
risk factor.
*Please note: in the original identification of potential risk or
protective factors to include in the multivariate final analysis, the
authors used the following P value thresholds to determine
potentially significant factors:
- P < 0.25: for the preliminary univariate analysis.
- P < 0.20: for the intermediary multivariate analysis.
These are very generous thresholds that increase the risk of a type 1
error (a false positive). While the authors are using this threshold as
an intermediary step to determine factors for inclusion in the final
statistical models, readers of the paper who are not familiar with
statistics may over-interpret tables 1 (pg. 199) and 2 (pg. 200) of this
paper, including drawing the inference that feeding canned food
significantly decreased the risk of a GDV.
Limitations:
It is not clear whether the GDV group included dogs that were
deceased as a consequence of the first GDV episode. It is possible
that referring veterinarians would not approach owners of dogs that
died or, alternatively, that owners whose dogs died were more or
less willing to be interviewed. This may have introduced bias into the
data set if survival rate from a GDV is associated with diet type fed.
4. Elwood (1998)
Population:
Irish Setter dogs (both sexes, neutered and entire) owned by
members of UK Irish Setter Breed Clubs.
Sample size:
669 dogs:
- 75 dogs that had had an episode of gastric dilatation and/or
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volvulus
- 594 control dogs
Intervention details:
A questionnaire was sent to members of UK Irish setter breed clubs,
and requested to complete one form per Irish Setter that they had
owned in the last ten years.
Demographic information included age, sex, neuter status and
whether the dog had ever had an episode of bloat/GDV.
Owners were requested to complete the answer by providing data
for the dog that applied at the time of the first GDV episode (GDV
dogs) or current data (control dogs).
A range of questions were asked about potential risk factors. These
included a range of dietary, environment, temperament and
exercise-related factors.
Of specific relevance to this PICO, the owners were asked what diet
they fed their dog.
Study design:
Cross-sectional study.
Outcome studied:
The outcome variable was whether an episode of GDV occurred. The
study then asked about a range of variables, in order to identify risk
factors that were associated with a GDV episode.
Of specific relevance to this PICO, the owners were asked what they
fed their dog:
Dry (unsoaked)
Dry (soaked)
Meat and biscuits
Proprietary tinned food (alone)
Proprietary tinned food (with biscuit)
Other (the owner was asked to provide details)
Main findings:
(relevant to PICO question):
Dogs fed a dry diet was no more likely to have an episode of GDV
than dogs fed other types of diet (Odds ratio: 1.97, 95% confidence
interval: 0.7 – 5.56, P > 0.05).
Nb. The initial univariate statistical analysis found that dogs that
were fed a dry diet were significantly more likely to experience a
GDV than dogs not fed a dry diet (Odds ratio: 2.13, 95% confidence
interval: 1.01 – 4.5; P < 0.05). However, once incorporated into a
multivariate analysis that included, where possible, the other risk
factors previously identified, the adjusted risk factor was no longer
significant. It is not clear which other risk factors were definitively
included in this multivariate analysis.
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Limitations:
The authors requested owners complete a questionnaire form for
every Irish Setter dog that they had owned in the previous ten years.
This poses a number of related issues for the data:
- The dogs may not still be alive. Thus, it is not clear how the
owners of the dogs not affected (the control dogs) could
complete the questionnaire as per the instructions as the
dogs may have been dead at the time of completion. Do the
owners then complete the form based on the management,
exercise, feeding, etc routines of the dog shortly before it
died, or when it was younger/fitter/healthier? If the owners
all elect for the form (as the closest point to ‘current’) this
could introduce significant biases into the data set.
- Up to ten years ago, is a long time to expect owners to
accurately reflect back and recall their dogs feeding,
exercise, housing regime, and so on. As the GDV group
owners were asked to recall this information from the time
the dog had its first episode of GDV, the length of time the
owners were required to reflect back could be even longer.
- The questionnaire is not sensitive to variations in feeding
regime. For example, the diet type fed may vary from day to
day, or over a longer time frame. Thus, any risk factor
identified may be arbitrary and true risk factors may not be
identified.
5. Raghavan (2004)
Population:
Dogs (male, female, neutered and entire) from eleven different large
and giant dog breeds (Akita, Bloodhound, Collie, Great Dane, Irish
Setter, Irish Wolfhound, Newfoundland, Rottweiler, Saint Bernard,
Standard Poodle, and Weimaraner), that were located within the
USA. Dogs were required not to have a medical history that included
an episode of GDV.
Sample size:
318 dogs:
- 106 dogs that developed a GDV
- 212 dogs that did not develop a GDV (the control group)
Intervention details:
This study used dogs drawn from a larger study (Glickman, et al.,
2000). The methodology for this study was as follows:
The study began in June 1994 and ended in February 1999.
Therefore, the maximum possible period that a dog could be studied
for was 58 months.
Dogs were recruited through breed clubs and dog shows. At the start
of the study, owners were asked about the presence of GDV in the
medical history of the dog or any of its first-degree relatives. The dog
was physically assessed for body condition and temperament, and
conformational measurements taken.
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Within thirty days of recruitment, owners were provided with a
detailed questionnaire to complete that provided data on the dog’s
GDV history (if positive, the dog was excluded), breeding, medical
history, reproductive status, personality and temperament, and
dietary factors.
Owners were instructed to notify the researchers if any of the
following outcomes occurred:
- The dog developed a GDV (if so, the researcher confirmed
this with the veterinarian who treated the dog)
- The dog died of another cause
- The ownership of the dog was transferred to another person
Owners were contacted in 1997, 1998, and 1999 to find out if, over
the duration of the study, their dog had developed a GDV and, if so,
whether the dog died or survived.
1991 dogs were registered at the initial state (dog show). Of these,
77 were excluded due to a previous history of GDV. The remaining
dogs (n = 1914) were enrolled on the study, of these, at least one
follow up was obtained for 1843 dogs and the detailed questionnaire
was completed for 1660. Of the latter group, 23 were excluded for
being less than six months old at the start. This left 1637 dogs o be
included in the analysis of this study.
At the end of that prospective study, there was sufficient
information on diet and ‘vital status’ (not defined by authors,
presumed to be GDV development and other demographic
information matched for in the current study), for 1634 dogs (of the
1637) to be potentially included in this study. Of these, all dogs that
developed a GDV (n=106) were included.
Dogs that developed a GDV during the prospective study were
divided into six groups based upon the calendar year in which they
developed a GDV (1994 – 1999*). The control group (n=212) was
then randomly selected to ensure that for each year, for each GDV
dog there were two control dogs that had been alive the year that
the GDV dog developed a GDV but who never themselves developed
a GDV.
*Nb. The original study (Glickman et al. 2000) states 1994 – 1999
(which would be six calendar years). The current study refers to
“follow – up ended in December 2000” (pg. 193) and six consecutive
calendar years of 1994 – 2000. However, it then directs the reader
back to the detailed study methodology described in the Glickman et
al. 2000 study for further details. This study does not refer to follow
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up data in 2000 and, indeed the study was published in January
2000. Thus, it is assumed that the current authors mean 1994 –
1999.
Study design:
Case-control study.
Outcome studied:
The outcome measure was whether the dog developed an episode
of GDV during the course of the study and whether it survived this
episode. The study then looked for factors that were associated with
an increased risk of developing GDV in the population studied.
Of direct relevance to this PICO, the authors’ asked the owners
about:
- The diet type fed to the dog (dry, canned, semi-moist,
unprocessed, home-prepared [raw versus cooked], table
scraps, treats)
Of potential relevance to this PICO, the authors’ also asked:
- Whether food was moistened before feeding
Main findings:
(relevant to PICO question):
There was no significant effect on diet type on risk of GDV.
- All of the dogs that developed a GDV (n=106) and all, bar
two, of the control dogs (n=210) were fed a dry diet as their
primary diet type.
- The median (range) percentage of metabolisable energy
derived from the dry component of the diet was similar
between controls (97.1, 0 – 100) and GDV cases (96.1, 59.5 –
100) (P = 0.99).
- Primary was defined as the dog obtained > 50% of its
metabolisable energy from this food type.
There was no effect of moistening the kibble on GDV risk (P >0.25).
Limitations:
Failure of the authors to report the findings of some of the data
referred to in the methods section limits the ability to interpret
some of the findings or draw conclusions.
The authors collect data on diet type fed at the start of the study
(within 30 days of recruiting dogs). No further attempts were made
to collect further data on this at regular intervals. Thus, unless diet
type fed is static and does not change over time, this reduces the
ability of the study to detect real effects or meaningfully explain the
effects observed.
All the dogs in the study (bar two) were fed dry food as the primary
diet type. Therefore, it is not clear how the study could evaluate
kibble as a risk factor as there were inadequate numbers of dogs in
each group (i.e. none in the GDV group and two in the no GDV
control group) fed an alternative diet type.
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6. Uhrikova (2015)
Population:
Dogs* owned by people who could read either Czech or Slovak
language. The survey was distributed within the Czech Republic
through various websites aimed at dog owners, some veterinary
clinics and dog shows, and by emailing owners through kennel and
large breed kennel club websites. However, survey distribution was
not restricted to the Czech Republic, so respondents came from a
wider geographic area, though predominantly Czech (90.7% of
respondents).
*The control dogs were dogs older than 5 years, and weighing > 30kg
and/or taller than 50cm, and had not had a gastroplexy performed.
It is not clear whether the same restrictions applied to the two GDV
groups (see below). However, it should be noted that, in the results
section, the study population overview indicates that this weight
restriction must have been lifted as the minimum weight in the
control, GDV – survivor, and GDV – died groups was 17kg, 20kg, and
17kg respectively (see limitations).
Sample size:
785 usable responses:
Control group: 536 dogs
Survived GDV group: 127 dogs
Died from the GDV group: 122 dogs
Intervention details:
The survey was comprised two parts:
Part A was accessible by all three groups of respondents; part B was
accessible only by owners of dogs who had had an episode of GDV
(regardless of survival).
Part A:
Demographic information included breed, age, sex, and weight was
requested.
A range of questions were asked about potential risk factors. These
included a range of dietary, elimination and exercise related factors.
Family history of GDV was also asked.
Of specific relevance to this PICO, owners were asked whether they
mainly fed:
- Kibbles
- Kibbles with liquid (water, soup, or other)
- Kibbles with meal (cooked or canned)
- Meal (cooked or canned)
- BARF (Bones and Raw Food)
- Other
For the purpose of analysis, the diets fed were merged into the
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following categories:
- Dry kibbles
- Meals with kibbles other than dry (presumably liquid added)
or other kinds of kibbles (not defined) and / or with the
additional of either canned or cooked food
- No kibbles in food
Of potential relevance to this PICO, the authors also asked about the
size of the particles of food fed as the diet:
- < 5mm (small)
- 5mm – 30mm (medium)
- > 30mm (large)
Part B:
Information was requested about the GDV episode.
Of specific background relevance to this PICO (i.e. was the dog
actually fed the usual diet immediately prior to a GDV developing?),
in part B, owners were asked about the last type of meal fed before
the dog developed a GDV.
Study design:
A cross sectional study.
Outcome studied:
The outcome variable was a) episode of GDV (yes/no?), and, b) of
dogs that developed a GDV, survived or died? The study then looked
for risk factors that were associated with these outcomes.
Of specific relevance to this PICO, the authors looked at different
diet types normally fed as potential risk factors for GDV
development. They also examined the type of diet last fed before
the dog developed a GDV. Of potential relevance, they also asked
owners about the size of the particles of food that comprised the
dog’s diet.
In the analysis, in calculation of the odds ratios, the relative risk
associated with feeding a diet with small or large particles was
compared to that of dogs fed a diet in which the maximum size fed
was medium sized particles.
Main findings:
(relevant to PICO question):
Part A of the questionnaire:
Dogs fed a dry kibble diet only were no more likely to have a GDV
episode than dogs fed other diet types/combinations (Odds ratio:
1.111, 95% confidence interval: 0.802 – 1.539, P = 0.527)
Dogs fed diets that did not contain any kind of kibble were
significantly less likely to have a GDV than dogs fed a diet containing
kibbles (dry kibbles, kibbles and canned food, or kibbles and cooked
food) (Odds ratio: 0.486, 95% confidence interval: 0.283 – 0.834, P =
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0.009).
Dogs fed large (> 3 cm) particles of food were significantly less likely
to have a GDV episode than dogs fed small (< 0.5cm) or medium (0.5
– 3cm) particles of food. Compared to medium particle fed dogs,
large particle dogs were 0.344 times as likely to have a GDV (95%
confidence interval: 0.224 – 0.529, P < 0.0001). There was no
significant difference in GDV risk between dogs fed small and
medium particles of dog food. Although the authors do not formally
analyse the small versus large categories, it should be noted that the
95% confidence interval for the small and large particle categories
overlap and so a significant difference was not observed between
these two categories:
- Maximum particle size < 0.5cm: odds ratio: 0.865, 95%
confidence interval: 0.425 – 1.761
- Maximum particle size > 3.0cm: odds ratio: 0.344, 95%
confidence interval: 0.224 – 0.529
Part B of the questionnaire:
77% of dogs that had a GDV were fed their usual diet type as their
last meal before the episode occurred. No further information
relevant to the PICO is supplied.
Limitations:
The authors do not specifically outline whether owners were
directed to record the biggest particles in the food before or after
soaking the kibble.
Although the questionnaire design allowed the authors to compare
dry kibble that had been moistened before feeding versus other
non-kibble based diets, before analysis the authors merged diet
categories into:
- Dry kibble only
- Meals with kibbles other than dry kibbles, moistened
kibbles, kibbles plus other food type, etc.
- No kibbles
As the non-dry kibbles category covered both moistened kibble only
diets and kibbles with any other diet type as well, this limits any
inferences that could be drawn versus the risk of dry kibble versus
moistened kibble in this diet.
The authors report that the control group was designed to be
restricted to > 30kg, the results section indicates that all groups
contained dogs weighing less than this. Furthermore, the authors
report that there were highly significant (P < 0.001) differences in
the median weight between the control group and the GDV groups,
but they fail to state the direction of the effect. However, the
authors chose to report their data using means and the range
(minimum – maximum values). The failure to report this data using
the median and inter-quartile range (it is assumed that, as a non-
parametric test was used, this data was skewed), means that it is
impossible to evaluate how these groups differed.
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Appraisal, application and reflection
Six studies were identified that purported to address the PICO either partially or fully. The findings of these
studies were mixed and of variable quality. However, no studies found that feeding kibble as a protective
factor reduced the risk of an episode of GDV. Teasing out the different potential aspects to this PICO (e.g.
dried kibble per se versus other diets; dry kibble versus moistened kibble, or diet fed immediately prior to
GDV versus the usual diet fed) was difficult or impossible to evaluate due to limitations or differences in the
study design. In some cases, diet type was described in terms of maximum particle size present in the diet,
rather than diet type. These studies and information have been included for the following reasons: the
author is unaware of any kibble diets that have kibbles that are bigger than 30mm; the authors report that
any diet containing the largest particles contained non-kibble components (thereby fulfilling the inclusion
criterion); the authors report other information that makes clear that some of these diet sizes were kibble
based.
Two studies should be removed from consideration before drawing any inference about the risk of GDV
posed by feeding a dried kibble diet (moistened and/or fed dry) per se. The first of these, Glickman et al.
(1997), intended to evaluate kibble as a risk factor, but found that almost all owners reported feeding their
dog (irrespective of whether the dog was in the GDV or control group) mainly a kibble diet. The authors
rightly note that, consequently, it was not possible to evaluate a dried kibble diet per se as a risk factor for
GDV as there is no comparator (for example, of non-kibble fed dogs, what proportion develop a GDV
compared to dogs fed a kibble diet?). It should be noted though that this study did identify the addition of
table scraps to a dog’s diet was a protective factor: dogs fed partially on table scraps had a significantly
reduced risk of GDV of 59%. The study design does not allow the reader to tease apart the owner feeding
regimes further so it is difficult to evaluate the impact of this finding in relation to the PICO. However, this
aspect of the study does not suffer from a lack of comparator so this finding should be taken forward to the
final evaluation. Although Ragahavan et al. (2004) report that there was no significant effect of feeding kibble
on risk of GDV, this study suffers from the same limitation as the Glickman et al. (1997) study as all, bar two,
of the dogs included were primarily fed on a kibble-based diet. The authors do extend their analysis by
exploring the proportion of metabolisable energy derived from the kibble component of the diet (to account
for mixed diet type feeding) to demonstrate that the proportions do not vary between groups, but this does
not remove the limitation described here.
Of the remaining four studies, the Pipan et al. (2012) study reports an impressive sample size (GDV group:
n=1114; Control group: n=1437) and reports that feeding a kibble diet significantly increases the risk of GDV.
However, the population that the authors elected to study was not restricted to large and giant breeds/sized
dogs (i.e. those which are considered to be at high risk of GDV). As the authors do not report requesting
information about the body weight of the dogs included in the survey, and there is no evidence to suggest
this in the results section, it is not possible to evaluate whether the two groups of dogs varied significantly
across this potentially important dimension. Consequently, the study findings should be approached with
caution as a potential source of relevant bias has been introduced into the methodology if large and giant
breeds are more likely to be fed a kibble based diet than small and medium sized breeds. As a dried kibble
diet tends to cost less than commercial diets containing a higher moisture content, and big dogs cost more to
feed than small dogs, the supposition of bias is reasonable. However, this study does also identify fish and
egg-based dietary supplements (but not table scraps) as a highly significant protective factor against risk of
GDV in dogs. Whether this finding is also a potential artefact of the sample population is not necessarily clear,
as the exact nature and form of the supplements is not clear. Are smaller dogs more or less likely to be given
supplements?
Uhrikova et al. (2015) also identified a dried kibble diet as part or all of the diet (but not dry, no liquid added
before feeding, kibble only versus other diet combinations) as a risk factor for GDV compared to feeding a
diet that contained no kibbles at all, however their study potentially suffers from the same criticism as the
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Pipan et al. (2012) study. Although Uhrikova et al. (2015) appear to be alert to the bodyweight issue (their
target control group definition attempted to restrict respondents to dogs weighing >30kg only), they were
unsuccessful in achieving this. All groups of dogs included dogs lighter than 30kg, but a highly significant
difference was observed in bodyweight between the control group and the two GDV groups (survived versus
died). However, the authors fail to state the direction of effect and their choice of measure of variation
(range) and central tendency (the mean is reported, despite using a non-parametric test to compare what
was presumably skewed data) does not allow the reader to assess the impact of this difference. As a
consequence, the findings of this study should also be viewed with caution in relation to the PICO. Uhrikova
et al. (2015) also found that a diet with particles of food in which the maximum size was >3cm was a
protective factor that reduced the risk of GDV compared with a diet containing diets in which the maximum
particle size was 0.5 – 3cm, but significant differences between the smallest particle sized diets (<0.5cm) and
the largest (>0.3cm) were not observed.
Of the remaining studies, the Elwood (1998) study most closely primarily addresses the PICO. Although a
smaller sample size than some other studies (GDV dogs: n=75; control dogs: n=594), the methodology utilised
by this study allowed the authors to examine the risk of feeding a kibble diet per se compared with other diet
types, and the effect of the kibble diet being fed dry or moistened. The initial univariate analysis identified
kibble as a potential risk factor; however, once other potential risk factors were built into the multivariate
analysis, this potential risk factor was no longer significant. The primary issue with this study is that the
authors requested that owners complete the form for any/all Irish Setter dogs that they had owned in the
previous 10 years (regardless of whether they had had an episode of GDV or not). As owners of dogs that had
had a GDV were instructed to answer the form by providing details of the dogs’ diet prior to the GDV
episode, some owners may have had to recall back an even longer period of time. Unless dogs are generally
fed a relatively unvarying diet type over an extended period of time, this may reduce the value of owner
recollection over such a long-time frame. The authors do not report data to allow the reader to evaluate
whether the two groups differed across the dimension of ‘how long ago the dog was last owned/alive’ (or
similar) to see if the demographics were similar between groups across this potential dimension. The
remaining study (Theyse et al., 1998) suffers from the same limitation in relation to the GDV group as they
retrospectively searched records over a 13-year time span, for GDV cases (which may have died many years
ago) and then contacted these owners to obtain, firstly, diet fed to the dog, and secondly, a sample of this
diet. This was compared to a control group recruited through a breed society. This study identified feeding a
diet with a maximum particle size of >30mm were significantly less likely to have a GDV than dogs fed a diet
containing a maximum particle size less than <5mm (of which 19 of the 23 dogs in this category were fed a
dry kibble diet only). If historical differences in trends in the type of diet fed were present (e.g. if dogs were
more likely to be fed a raw diet in present time (at the time the study was conducted) than over the 13-year
time frame studied, then this could have skewed the data in the direction described as the present-day dogs
would have been primarily control group dogs. Uhrikova et al. (2015) also found that feeding large particles
of food had a protective effect against GDV and this study did not suffer the Theyse et al. (1998) limitation
described. However, the strength of the Uhrikova et al. (2015) study in supporting the Theyse et al. (1998)
finding is weakened by the lack of transitive inference in their data, as no other size categories were
significant (i.e. small > medium, and crucially small > large were not identified as relative risk factor
relationships).
In conclusion, most of the studies that form a part of this PICO contained limitations that meant that they
cannot specifically address the PICO due to a lack of comparator (Glickman et al., 1997; Ragahavan et al.,
2004), or viewed with considerable caution with regards to any significant effect of kibble feed due to issues
with the population surveyed or reported (Pipan et al., 2012; Uhrikova et al, 2015). Of the remaining two
studies, the findings are not in agreement with one study (Theyse et al. 1998) concluding that there was no
effect of kibble, and one concluding that, relative to feeding diets with large particles, diets that were small
particle sized (mainly dry kibble only feeders) were significantly more likely to experience a GDV. However,
the long time frame over which owners were potentially asked to recall back (Theyse et al., 1998; Elwood,
1998), and the requesting of a diet sample for a dog that may have died up to 13 years ago (Theyse et al,
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1998) mean that these findings should not be accepted uncritically. However, the Glickman et al. (1997)
finding that table scraps significantly reduced the risk of GDV does provide some support for the alternative
claim that feeding alternative diets may be a protective factor. However, there is a need for further research
in this area, with adequate numbers of dogs being fed specific, identifiable, alternative diets (e.g. primarily
raw, primarily home-made cooked, etc) in order for these hypotheses to be tested. The preponderance of
dogs being fed primarily a kibble diet (based on the studies evaluated) may make this more problematic to
investigate. Though as a consequence, the balance of unevaluated evidence supports the claim that kibble is
a risk factor for GDV (and that non-kibble based diets or kibble plus non-kibble supplements or dietary
additions may be a protective factor that reduces the risk of GDV), in practice, there is insufficient adequately
controlled evidence to demonstrate this clearly.
Methodology Section
Search Strategy
Databases searched and dates
covered:
Pubmed; Science Direct (all years, restricted to journals); Web of
Science; CAB Abstracts. (1973-2016).
Search terms:
(dogs OR dog OR canine OR canines OR canid OR canis OR bitch)
AND ("gastric dilatation" OR "gastric dilation" OR "gastric dilatation
volvulus" OR GDV OR "gastric torsion" OR "stomach volvulus") AND
(feed* OR diet OR diets OR dietary OR food OR kibble)
Dates searches performed:
29th March 2017
Exclusion / Inclusion Criteria
Exclusion:
Pre-defined exclusion criteria: non-English language, popular press
articles.
Inclusion:
Any comparative (control group utilised) study in which the effect
of diet type* on development of a gastric dilatation (+/- volvulus)
was investigated.
*Diet type must refer to a dry or kibble based diet, plus at least one
other type of diet in order for the study to be included.
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Search Outcome
Database
Number
of
results
Excluded
– did not
address
the PICO
Excluded – not
English
language
Excluded –
conference
abstract only
Excluded –
duplication
Total
relevant
papers
NCBI PubMed
35
30
0
0
0
5
Thomson
Reuters Web
of Science
35
28
1
0
5
1
CAB Direct
58
50
1
1
6
0
Science Direct
343
343
0
0
0
0
Total relevant papers when duplicates removed
6
CONFLICT OF INTEREST
The author declares no conflict of interest.
REFERENCES
1. Elwood, C. (1998) Risk factors for gastric dilatation in Irish setter dogs. Journal of Small Animal
Practice, 39 (4), pp. 185 – 190. http://dx.doi.org/10.1111/j.1748-5827.1998.tb03627.x
2. Glickman, L. et al. (1997) Multiple risk factors for the gastric dilatation – volvulus syndrome in dogs: a
practitioner / owner case – control study. The Journal of the American Animal Hospital Association, 33
(3), pp. 197 – 206. http://dx.doi.org/10.5326/15473317-33-3-197
3. Glickman, L. Glickman, N. Schellenberg, D. et al. (2000) Incidence of and breed – related risk factors for
gastric dilatation – volvulus in dogs. Journal of the American Veterinary Medicine Association, 216 (1),
pp. 40 – 45. http://dx.doi.org/10.2460/javma.2000.216.40
4. Pipan, M. Brown, D. Battaglia, C. et al. (2012) An internet – based survey of risk factors for surgical
gastric dilatation – volvulus in dogs. Journal of the American Veterinary Medicine Association, 240 (12),
pp. 1456 – 1462. http://dx.doi.org/10.2460/javma.240.12.1456
5. Raghavan, N. Glickman, N. McCabe, G. et al. (2004) Diet – related risk factors for Gastric Dilatation –
Volvulus in dogs of high risk breeds. Journal of the American Animal Hospital Association, 40 (3), pp.
192 – 203. http://dx.doi.org/10.5326/0400192
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6. Theyse, L. van de Brom, W. and van Sluijs, F. (1998) Small size of food particles and age as risk factors
for gastric dilatation volvulus in Great Danes. Veterinary Record, 143 (2), pp. 48 – 50.
http://dx.doi.org/10.1136/vr.143.2.48
7. Uhrikova, I. Machackova, L. Rauserova – Lexmaulova, L. et al. (2015) Risk factors for gastric dilation
and volvulus in central Europe: an internet survey. Veterinarni Medicina, 60 (10), pp. 758 – 587.
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