• Control group (dogs without a GDV): 1437 respondents
• Gastric dilatation – volvulus group (GDV): 1114 respondents

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:
   1. Dog specific factors
   2. Management factors
   3. Environmental factors
   4. 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 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.

Of relevance to this PICO, the authors’ asked owners to rate, on a scale of 1 to 5, the speed with which their dog consumed its food ration.

The measurement of speed of eating on a scale of 1 -5 will be sensitive to owner subjectivity in assessment. The authors do not provide any information on how owners were guided (if at all) to select the number that most represented their dog. Further, the incidents of GDV were retrospective so owners may have already taken measures to reduce their dog’s speed of eating post-surgery, on the basis of veterinary recommendation or lay research. The authors do not outline whether owners were asked to complete the form on the basis of the dog’s feeding behavior at the time of (or preceding) the GDV, or present time, or not directed as to a time frame to use.

There was no attempt to match control dogs and GDV dogs across other dimensions that may have been relevant (e.g. breed, size, and / or age).

The population of dogs studied is not constrained to types of dogs at high risk of GDV (large and giant breed dogs). Therefore, if any risk factors identified co-vary with the size of the dog, this would represent a confounding variable in interpreting the data that limits any conclusions that may be drawn.

1637 (large breeds: n= 894; giant breeds: n = 743):

• Dogs that developed a GDV during the course of the study: 98
• Dogs that did not develop a GDV during the course of the study: 1539

Nb. This study was derived from a larger prospective cohort study carried out by the authors. 1991 dogs initially enrolled on this study; however, for inclusion in the current study (which used data from the larger study), certain criteria needed to be met and this reduced the sample size. Further details are outlined in the intervention section.

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.

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.

This was the methodology for the original prospective cohort study by the authors (referred to above). Dogs from that study were included only if:

• The initial questionnaire had been fully completed
• There was at least one follow up set of data for that dog
• 7% of the owners in this study fulfilled both criterion for inclusion (n = 1660)
• 4% of these owners were excluded because their dog was less than 6 months old at the point of completing the initial questionnaire, leaving 1637 (82.2% of the original sample) available for analysis in this study.

Of these dogs, the median duration during which the dogs were followed up was 2.4 years (Max: 4.8 months; minimum: no stated). The reasons for loss to follow – up (other than death) are not stated. 182 dogs died during this period: 29 died due to the GDV episode, 24 died for unknown reasons. 55 are reported to have died from other medical problems. 74 dogs are not accounted for in the figures reported.

The authors converted the raw data into number of GDV cases per 1000 dog years in order to present the data as incidence of GDV (± confidence interval) among the large and giant breed dog population.

Of relevance to this PICO, the authors’ asked owners to rate, on a scale of 1 (slow) to 10 (fast), the speed with which their dog consumed its food ration. The authors did not direct the owners further as to what constituted e.g. a rating of ‘3’, but, instead, the owner was left to use their judgement and experience.

In analysing and presenting the data, the authors’ merged speed ratings to form three categories:

1. Slow: speed rating of 1 – 3
2. Average: Speed rating of 4 – 6
3. Fast: Speed rating of 7 – 10

And then, further split the data into:

1. Large breed dogs
2. Giant breed dogs

• Large breed dogs that ate quickly were 2.36 times more likely to develop a GDV during the study than dogs that ate slowly.
• The incidence (± confidence interval) of GDV episodes per 1000 dog years was:
  • Slow eaters: 13 (2-24)
  • Average eaters: 23 (13-33)
  • Fast eaters: 30 (19-41)
• 8% of GDV cases could be explained by the dogs eating fast.

Giant breed dogs:

• No statistically significant association was found between speed of eating and risk of GDV in Giant breed dogs.
• The incidence (± confidence interval) of GDV episodes per 1000 dog years was:
  • Slow eaters: 36 (12-60)
  • Average eaters: 29 (15-43)
  • Fast eaters: 22 (12-32)

The authors collect data on eating speed 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 speed of eating is an unchanged behavior of the individual dog and not influenced by other factors (e.g. diet change, age, etc), this reduces the ability of the study to detect real effects or meaningfully explain the effects observed.

The measurement of speed of eating on a scale of 1 -10 will be sensitive to owner subjectivity in assessment.

The total number of dogs lost to follow up is not reported. The authors exclude dogs from the original study that were lost to follow-up before at least one follow up questionnaire was completed. However, this is not the same as saying these dogs were not lost to follow-up as, for example, if the study was still in operation, why were further questionnaires not completed by these owners? The authors do not report how many dogs recruited to the study, remained with the study until the study ended. Instead they report only median duration of follow-up; this is meaningless to assess the number of dogs that remained with the study from recruitment to study end, as the dogs were signed up to the study at different time points. If the dogs that developed GDV and the dogs that didn’t develop a GDV differentially dropped out prematurely, this could introduce a ‘loss to follow-up bias’. We know that, by the nature of the recruitment process for the subset of dogs included in this study, that already 13.3% of dogs had been excluded due to lack of follow-up data (no follow-up questionnaires completed). Therefore, it seems likely that total losses to follow-up before the study ended would be higher (and possibly considerably so) but the authors fail to give us the information needed to assess this.

There is not attempt by the authors to assess whether participant drop out before the study ended was random or whether particular risk factors or characteristics were associated with an increased risk of drop out. Furthermore, there are a lot of dogs lost to death that remain unaccounted for in the authors’ reporting.

• 38 dogs that had presented at the authors’ vet clinic with a GDV
• 71 dogs owned by members of a Great Dane breed society

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).

No further information is provided.

• Owners were not specifically asked to measure length of time taken so it probably represents a variable and subjective assessment
• The authors also ask owners whether they feed their dog once, twice or more often per day. Dogs that consume several meals will have smaller portions per feeding session and so be more likely to consume a ration within five minutes. Therefore, there may be a partial confound in the findings between size of portion and time taken to consume the ration. This weakens its use as a measure to assess speed of eating.
• There is no evidence that the authors tried to control for this statistically (e.g. by only analysing the dogs that were fed once daily).

The authors provide no numerical data to support their assertion that there was no significant effect of food intake time.

The authors retrospectively searched clinic records for GDV cases in Great Danes between 1981 and 1994 and owners of affected dogs contacted to complete a questionnaire that retrospectively assessed feeding and exercise regime.

• Thus, owners were often being asked to recall information about their dog’s exercise and diet regime many years after the GDV episode and / or likely death of their dog. Factual recall is likely to be poor under these circumstances. 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.

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 – control 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 rate of eating. This is mentioned in the abstract and results section but the authors fail to mention in the methods section either rate of eating per se or how this was assessed by the owners or quantified by the researchers. In the results section, the authors refer to slow, moderate, and fast groupings in relation to rate of eating, but how dogs were allocated to these groupings remains unclear.

Compared with slow eaters, dogs that ate moderately fast were 2.59 (1.01 – 6.79, 95% confidence interval) times more likely to have developed a GDV. Fast eaters were 4.72 (1.57 – 14.24, 95% C.I.) times more likely to have developed a GDV, than slow eaters.

It is not clear how many dogs (total; GDV; case-controlled pairs) were represented within each of the groups (slow, moderate, and fast).

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 speed of eating.

• 75 dogs that had had an episode of gastric dilatation and / or volvulus
• 594 control dogs

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.

There is insufficient information as to whether this was objectively quantified (i.e. authors provided a descriptor for how fast each dog should eat in order to be awarded a given score). Or, whether this represented a subjective impression of the dog’s feeding behavior.

The median (1^st quartile – 3^rd quartile) score for speed of eating was 6 (5 – 8) for the GDV dogs, and 7 (2.1 – 8) for the control dogs.

• 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.

There is not enough information supplied regarding the speed of eating score to allow further criticism of it.

• 106 dogs that developed a GDV
• 212 dogs that did not develop a GDV

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 to be potentially included in this study. Of these, all dogs that developed a GDV (n = 106) were included.

A nested case control study design was used so dogs that developed a GDV were placed in one of six groups (corresponding to the year – 1994 – 2000 - they experienced the episode of GDV). The dogs that made up the control group (n = 212) were placed into one of six groups according to the year they joined the study (i.e. the year they completed the detailed questionnaire about diet, etc). From each of these year groups, for every GDV case that occurred in that year group, two dogs were randomly selected to act as controls. This was done to ensure that the diet related information (including the estimation of how fast the dogs ate) was collected at a similar time for both GDV dogs and control dogs.

Of relevance to this PICO, the authors asked owners to rate, on a scale of 1 (slow) to 10 (fast), the speed with which their dog consumed its food ration. The authors did not direct the owners further as to what constituted e.g. a rating of ‘3’, but, instead, the owner was left to use their judgement and experience.

To analyse the data, dogs from each group were split into two groups: slow eaters (score: 1-3); moderate speed eaters (4-6); fast eaters (7-10) and odd ratios calculated based on difference from moderate eating. Thus, both slow and fast rates of eating were evaluated as a risk factor for GDV.