Bloat: Identifying Risk Factors and Preventive Measures



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Although much research remains to be done to understand bloat (Gastric Dilatation - Volvulus) in dogs, significant advances have been made. Current scientific research does indicate that bloat is a dietary disease. Although specific causes of bloat are not known, identifying risk factors and high-risk dogs will help dog owners adopt preventive measures.

Gastric dilatation-volvulus (GDV), often called bloat or gastric torsion, is a complex disorder which usually occurs as a lifethreatening emergency. Bloat is characterized by expansion of the stomach with gas or frothy material (dilatation). The stomach will not empty normally. In the stomach of a dilated dog it is difficult for food to advance into the intestines, nor will food pass in the other direction as vomit.

Dilatation can be followed by a rotation of the stomach (volvulus or torsion), which effectively closes both the entry to and exit from the stomach, so that relief of the distended state is not possible. This rotation compresses one of the major veins carrying blood to the heart, severely depressing normal blood circulation. This condition can rapidly lead to shock and death. Bloat can be sudden and devastating in an apparently healthy dog. Hereditary predisposition has been suggested in certain instances. However, conclusive documentation is difficult to obtain because of the sporadic nature of GDV.

New Studies Focus On Risk Factors
Recent studies provide new insight into risk factors associated with bloat. Analysis of Risk Factors for Gastric Dilatation and Dilatation - Volvulus in Dogs by Dr. Lawrence Glickman, et. al., the Department of V eterinary Clinical Science at Purdue U ni versity, was published in the May 1, 1994 issue of The Journal of the American Veterinary Association.

This study is based on bloat cases from 12 veterinary hospitals. Abstracts of medical records were obtained for 1,934 dogs with bloat (cases) and 3,868 dogs (controls) with other diagnoses. Only initial rather than reoccurring bloat cases were included in the study. The case and control groups were compared in order to evaluate factors which might have influenced the risk of developing bloat.

The Purdue study defined risk factors as any aspect of life style or behavior, environmental exposure or inherited characteristic that is associated with the occurrence of a disease. That is, any characteristic observed more frequently in the group with bloat than the control group.

Risk Factors Identified
The Purdue study identified these factors which influence the risk of developing bloat:
  • Increasing age was a significant risk factor. Dogs older than seven years were at least twice as likely to have bloat as dogs two to four years of age.
  • Actual body weight was found to be less important than expected body weight based on breed standards as a risk factor for bloat. There are many health care reasons to prevent obesity in dogs such as cardiovascular problems and strain on muscles and joints. However, as a strategy to help prevent bloat, attempts to reduce a dog's body weight by caloric restriction would probably have little effect.
  • Purebred dogs were more likely to develop bloat than were mixed breed dogs.
  • No significant association of bloat with sex orneuterlspay status was found.
  • The six more common breeds with the highest risk of bloat were Great Dane, Weimaraner, Saint Bernard, Gordon Setter, Irish Setter and Standard Poodle.
  • Less common breeds with a high risk included the Irish Wolfhound, Borzoi, Bloodhound, Mastiff, Akita and Bull Mastiff.
  • Body conformation, particularly a narrow and deep thoracic cavity, increased the risk of bloat for specific breeds.

    Other Findings
    The frequency of bloat among all dogs admitted to the different hospitals in the Purdue study ranged from 2.9 to 6.8 per 1,000 dogs.

    A total of 28.6 percent of the dogs with gastric dilatation and 33.3 percent of those with dilatation and volvulus died in the hospital.

    Study of Feeding Practices, Behavior Provides New Insight
    Another study conducted at the Virginia-Maryland Regional College of Veterinary Medicine by Dr. Neal Bataller involved over 700 dogs presented at nine veterinary hospitals. Of these dogs, 244 were bloat patients. The other dogs were admitted for other reasons and provided the control group for the study. This study looked at diet and behavior and their relationship to bloat and presents new observations about feeding and water management. A number of different diets and feeding strategies were represented in the study. Based on this study, Dr. Bataller believes that diet tends to be overemphasized as a cause of bloat. Preliminary results identified several risk factors.

    In the study, dogs fed once a day were at no greater risk than those on any other feeding frequency. However, Dr. Bataller cautions that this is preliminary information. Additional studies are needed to verify it.

    Nervous Dogs at Risk
    Dr. Bataller's findings suggest that the more nervous the dog, the more at risk. Dogs in the study were defined by their owners as calm, normal, nervous or very nervous. Normal dogs were almost twice as likely to develop bloat as compared to calm dogs. Very nervous dogs were 12 times more likely to be at risk.

    Based on behavior reported by owners, the dogs with bloat have behavior patterns that showed the dogs ingesting large amounts of air.

    Dogs in the study that gulped water were twice as likely to get bloat as dogs that lap water normally. Many owners of dogs with bloat also reported that their dogs panted or belched excessively before bloating.

    Stress Implicated
    Other findings in the study suggest that many kinds of stressful events are often associated with the onset of bloat such as a trip, the excitement of a picnic, a thunderstorm, and kenneling. While it is virtually impossible for a dog owner to prepare a dog for all stressful situations, helping a dog ease into such situations is desirable. For example, if a dog is to be kenneled, accustom the dog to spending more hours in his dog crate and having limited access to exercise prior to being boarded.


    • Time of Bloat Occurrences
    According to Dr. Bataller, the time of day appears to have an influence on the occurrence of bloat. Among the dogs in his study, few incidents occurred during the morning hours. Incidents of bloat increased throughout the day and peaked at late evening. In discussing his study, Dr. Batallar added that he hopes owners of dogs at risk for developing bloat and dogs who have experienced bloat will consult with their veterinarian concerning the merits of gastropexy, a preventive surgical procedure.

    Research Disproves Old Diet Theories
    Historically, some researchers theorized that cereal-based dry dog foods, and soybean meal in particular, might be involved in the cause of GDV due to the fermentation of food by bacteria in the stomach. The theory was that fermentation would be followed by release of large quantities of gaseous products such as carbon dioxide, methane and hydrogen. However, considerable research has shown this is not true.

    A study conducted at the University of Minnesota examined the gas accumulated in the stomachs of dogs with bloat. This study showed that the source of gas was swallowed atmospheric air rather than fermentation, as the original proponents had suggested. Several other studies have indicated that atmospheric air is the main source of gas in the digestive system of normal animals. Additional support for this research is the fact that fermentation occurs primarily in the intestine, not in the stomach. Consequently, it cannot contribute to bloat.

    Studies at the University of Florida have failed to demonstrate any effect of diet on gastric function in large breed dogs, suggesting that diet is probably not a cause of the disease.

    Other Research Perspectives
    Some researchers feel that the basis for bloat may be a disorder of motility of the stomach or the control of motility. They theorize such a defect might predispose to delayed or abnormal emptying of the stomach after eating, chronic overstretching of the stomach, alterations in supportive structures, excessive swallowing of air and eventually dilatation and volvulus.

    The Journal of Small Animal Practice (1990, Volume 31) published a paper by C. F. Burrows, et.al., University of Florida, College of Veterinary Medicine, stating that "current thinking suggests that the final common pathway in the development of GVD may be an inhibition of gastric motility and emptying. This could come about through a primary disruption of normal gastric electrical patterns or through the effect of extraneous stressful events that disrupt gastric motility."

    Bloat affects primarily large and giant breed dogs, presumably because of their anatomy or conformation. This factor has led some researchers to suggest that the stomach in deep-chested dogs has excessive room to move about or twist. It is also suggested that the stomach anatomy or function is different in large breed dogs. Heredity may play a role by influencing the dog's anatomy.

    Although many important clues exist as to the causes of bloat, research must continue to achieve a complete understanding of this disease.

    Warning Signs of Bloat
    Bloat can strike an apparently healthy dog without warning. For this reason, a dog owner should be aware of the following warning signs of bloat:
  • A sudden display of discomfort is the first warning. The dog may whine, pace, sit and get up again in an unsuccessful attempt to be comfortable.
  • Frequent attempts to vomit produce no result.
  • The abdominal pain and distention become more evident.
  • The dog may not be able to get up.
  • Signs of shock become evident: pale gums, rapid heartbeat and irregular, shallow breathing.

    Bloat is life threatening and emergency treatment must be obtained immediately. Do not wait for signs to progress before seeking veterinary care.

    As a safeguard, whenever a dog shows signs of illness, prompt veterinary treatment is recommended.

    Preventive Measures
    While no measures can guarantee to prevent bloat, the following strategies have been suggested to help reduce the risk:
  • Feeding should not be preceded or followed by exercise.
  • In a multi-pet household, feed dogs individually in a quiet place. This may help calm dogs who gulp their food or feel they have to protect it while eating.
  • Feeding two or more small meals a day is recommended.
  • Avoid sudden dietary changes. If it is necessary to change a dog's diet, it should be done gradually over a seven to ten day period.
  • Feed only a high quality dog food. Avoid feeding table scraps or supplements of any kind. Prevent access to other sources of food such as garbage cans.
  • Dogs who habitually gulp their food may benefit by mixing dry food with water. This increases the volume and helps to slow them down.
  • Keep the dog as quiet as possible before and after eating.
  • Do not allow a dog to drink water immediately after exercise or undue excitement.
  • Try to avoid or alleviate situations stressful to the dog such as loud rock music or the excitement of large gatherings.
  • Disrupting a dog's regular routine should be avoided or minimized as much as possible.
  • When a dog is boarded, the kennel personnel should be instructed as to the diet to feed and how much to feed. The importance of not changing the dog's diet or feeding routine should be emphasized.

    In establishing a breeding program, consideration should be given to the possibility of hereditary predisposition to bloat as the result of body conformation or physiological control of the digestive function of the stomach.


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