There is little known as to why dogs, especially the large and giant breeds, may experience this condition. My wonderful boy, Ben, was lost to this awful unknown… it is a devastating way to lose a pet and a hard loss to deal with. Despite not having any real understanding as to what causes ‘Bloat' it is a known fact that time is of the essence when a pet shows the first signs of it.
What is Bloat?
Gastric Dilatation Volvulus (GDV):
Commonly referred to as bloat or torsion of the stomach. This condition can sneak up quickly and is often fatal. Affected dogs suffer extreme pain and their abdomen can swell to an immense proportion.
Bloat is a series of events. Air (sometimes fluid) accumulates in the stomach and this causes dilation of the stomach. The volvulus (torsion) happens when the dilated stomach twists, cutting off any way for the air to escape. On one end, the stomach closes at the esophagus and on the other end access to the small intestine is sealed. The stomach is now effectively isolated. As the condition progresses the ever enlarging, twisted stomach starts to put pressure on the blood vessels. Often these blood vessels will twist as well, hindering blood flow to the heart and lungs. If the flow of blood to the heart is decreased, then an insufficient amount of blood is reaching the rest of the dog's body. Soon tissues are deprived of oxygen, and undergo necrosis (this is especially true of the stomach wall). Death soon follows.
Three stages of Bloat:
Stage 1 – The earliest of the signs is a restless dog. They may pace continually, or get up and then lie down only to repeat the process. If caught early, the chances for recovery are good.
Stage 2 - Excessive salivation is often noticed, as well as panting and unsuccessful attempts to vomit. As the condition continues the abdomen noticeably swells and feels tight like a drum. (It is important to note that not all dogs that bloat have a distended stomach) At this stage, survival is about 50/50.
Stage 3 - The dog will then go into shock (weak, pale gums, shallow pulse) and then into a coma with death as the ultimate outcome if the condition goes unnoticed or untreated. The fatality rate of GDV runs at about 29%. Survival at this point is little to none.
Usually the time frame from Stage 1 to Stage 3 is about a 2-3 hour window and once a dog is in Stage 3, the chances for survival are slim. By this point, the internal damage is so severe that it is irreparable.
Research on Bloat:
You would think that since Bloat is a leading cause of death in giant and large breed dogs that there would be substantial research into the causes for this disorder. But this is not the case and only a few researchers are investigating its causes. Most of the studies deal extensively with treatments and not the actual cause. Dr. Glickman, a researcher and teacher at Purdue University has been the recipient of numerous awards and has authored over 175 scientific articles on canine health. His most recent research was undertaken to isolate risk factors in order to identify environmental situations and characteristics that make dogs more susceptible to GDV. In this study he followed nearly 2,000 dogs belonging to 11 breeds for up to five years to determine which would develop bloat and which would not. He then took all the data he had accumulated and related it back to things such as: the breed of dog, size, shape, personality, age, genetics, dog's diet and how the dogs were managed. Analysis is still ongoing.
The first part of the study, He tried to look at characteristics that would put one breed at a higher risk for Bloat than another. He characterized large breed dogs as those that weighed between 50 and 99 pounds at adult weight and giant breed dogs as weighing more than 99 pounds as adults. He did not study smaller breeds as they are not as prone to bloat. He included 11 breeds, chosen because they were well known to be at high risk for GDV ( Akita , Bloodhound, Collie, Great Dane, Irish Setters, Irish Wolfhound, Newfoundland , Standard Poodle, Rottweiler, St.Bernards, and Weimaraners). Though Labrador Retrievers were not included in this study the results are still valuable and can be applied to all breeds. The dogs used were measured at AKC shows and breed size, breed shape, temperament, aging and genetics were the characteristics analyzed. As a side point… a purebred dog is 3 times more likely to bloat than a mixed breed but not sure as to why.
Dr. Glickman found the incidence of bloat was high and nearly identical between large and giant breed dogs. Fatality rate of those that developed bloat was 29%. The highest risk breed was the Great Dane with a 42% risk of bloat in their lifetime and the Labrador Retrievers with only a 2% risk of bloat. For large breed dogs the rate of Bloat was 23% and for the giant breed dogs the rate of Bloat was 26%.
The breeds that have a deeper and narrower abdomen are at greater risk. The abdomen depth/width ratio is a much stronger predictor than the chest depth/width ratio for Bloat. The deeper and narrower the abdomen is… the greater the room for the stomach ligaments to stretch down or lengthen as part of the aging process. So the deeper abdomen provides more room for the stomach to actually descend with age. This combination of stretched ligaments and greater room allows the stomach to twist.
It was found that personality turned out to be a great predictor of Bloat at the breed level. Owners were asked to rate their dogs on a scale of 1 to 10 for traits such as aggression to people, aggression to dogs, submission to people, submission to other dogs, excitability, fearfulness, happiness, trainability and whether dogs were easily upset by new situations. Two very clear trends emerged, 1) The more fearful the breed, the higher the risk of bloat and 2) the more easy going the breed, the lower the risk. The doctor also points out that it is not the amount of stress a dog experiences but how the animal's body reacts to it. He says when animals are put under stress certain stress hormonal and neuronal responses occur. And some of these responses clearly affect gastric motility. So, a fearful dog may have a very different response physiologically to stress than a happy dog. It's possible that those physiological responses may contribute to the rotation of the stomach because of the gastric motility.
Dogs of all ages were included in the study but the incidence of Bloat increased with advancing age. As with most diseases, bloat can occur at any age but the rate increases as the dog ages. This means we have to think about how bloat ties into the aging process. In large breed dogs the incidence of Bloat increase dramatically after 3 years of age. In giant breed dogs the increased incidence starts significantly earlier.
It is not believed bloat is genetically based in the sense that one gene can cause bloat, but the inheritance of certain traits and characteristics predispose breeds or individual dogs to bloat. The strongest recommendation to prevent Bloat is to NOT breed a dog that has a first-degree relative that has had GDV. Results of this study suggest that the incidence of GDV could be reduced by approximately 60%.
Individual Dog Analysis:
The second part of the study, Dr. Glickman looked at individual dogs to see why those dogs were at increased risk compared to other dogs in the study. Risk factors that were analyzed included gender, neutering, weight, diet, speed of eating, belching and flatulence and genetics. It included environmental factors such as housing, restriction of water/exercise around feeding time, elevated food bowls, moistening food, preventative medication and number of meals fed.
Only minor differences in the risk of Bloat between males and females. The males had a 14% higher incidence than females.
Not a factor in the risk of bloat.
This factor proved to be significant. Dogs that have been categorized as chronically underweight by their owners are at a higher risk than dogs characterized as average or overweight. It is suggested that while bloat occurs acutely in dogs that show no previous indications that they will, bloat, these dogs may in fact have problems with their gastrointestinal tract long before they bloat. This may explain why they are thin. The weight factor could also be attributed to underlying GI tract problems or the fact that it is hard to keep weight on fearful dogs.
Individual dog analysis also looked at different foods, the brand, the amount, the size of the kibble, fat preservatives used, canned, dry, semi-moist etc. Because this area was of such great magnitude the final analysis has not yet been completed. It is important to note that there have been previous studies where dog kibble smaller than 30mm were associated with an increased risk of developing Bloat.
Speed of Eating:
The faster the dog ate, the greater the risk of bloat. This is believed to be a result of the excess air being gulped. One theory as to the cause of bloat has always been attributed to the speed at which a dog eats. However, the fact that many dogs that bloat do not do so immediately after eating seems to refute this widely held thought. This is perhaps the most confusing aspect when studying GDV. Researchers have tried to determine why the stomach fills and distends so rapidly, and most bloat does not occur immediately after eating. In fact about 70% of cases of bloat occur late at night or early in the morning. Researchers know that what is in the stomach is air, and that air can only come from one place… It has to be ingested. So the issue now becomes what causes some dogs to ingest large amounts of air and others not to. This suggests that there is some underlying problem that does not just occur during an acute episode, but that happens repeatedly and is exacerbated by temperament. Often, dogs that don't cope well will gulp. There is also a study in the works funded by the Collie Club of America that will look at abnormal esophageal motility in dogs. A European study found that the vast majority of dogs with repeated episodes of bloat have defects in their swallowing mechanism. If they can find the defect they may be able to test (Barium fluoroscopy) for it to see if their dog is at high risk for GDV.
Owners were asked to characterize their dogs in terms of flatulence and belching to see if they were also associated with greater risk of Bloat. It was found that in dogs that belch often had about a 60% increase in risk of Bloat. In dogs that had flatulence often there was a 20% increase in risk. Dogs that had abdominal distention regularly after eating had an 80% increased risk. Dr. Glickman believes that GDV is caused by excessive air swallowing, so the belching and the flatulence may not be gas but may in fact be air. He thinks that maybe the same mechanism that leads dogs to bloat, may also lead to the belching and flatulence.
One of the strongest predictors for Bloat was having a first-degree relative that bloated. A first degree relative is defined as a parent, sibling, or offspring, dogs that shared 50% of their gene pool. Pedigree analysis is difficult because Bloat may not manifest itself until the dog is 7 - 10 years old. This type of analysis would be quite difficult, but would give a wealth of information to uncovering hereditary tendencies that are not easily obtained when asking only about first degree relatives.
In earlier studies, environmental changes such as a dog being boarded, having strange people in the house, changing residences, etc. increased the rate of Bloat.
A common practice to prevent bloat that many people have utilized includes restricting exercise or water intake immediately before or after eating. This advice has become almost 'common sense'. However this study found that this was not associated with a reduced incidence of Bloat, but in fact there was even a slight increase in the rate of Bloat for dogs whose owners restricted water and or exercise around meal times.
Elevated Food Bowls:
A common thought found on the internet, in dog food pamphlets, and in popular dog magazines, is that raising the food bowl for dogs that eat quickly will help reduce the air that is gulped. However, raising the food bowl has appeared to significantly INCREASE the risk of Bloat and not decrease it as was previously thought.
This is a common practice for many people that are trying to prevent an occurrence of Bloat and several studies have shown there may be an increased risk of Bloat with moistened food. This needs further study.
Owners of high-risk breeds may try to medicate their dog to reduce gas formation or increase gastric motility in order to help stave off Bloat. These efforts do not appear to reduce the incidence of Bloat. The only real preventative medicine would be to tack the stomach in place prior to a Bloat event occurring.
Number of Meals Fed:
Another common recommendation for preventing Bloat is feeding smaller meals more often throughout the day. It has been found that as the number of meals increased, the risk of bloat decreased. According to that, you could make the conclusion that free feeding is best. Most people do not free feed large or giant breed dogs so this conclusion is only speculation. Although I can tell you first hand, Ben was free fed and it didn't help him. It is assumed that the reduced incidence of bloat relates to less distension of the stomach with smaller meals.
Things to Help Possibly Reduce the Risk:
1) Don't breed a dog if a first degree relative has suffered an episode of bloat.
2) Owners that have dogs that eat rapidly should do anything they can to slow them down (what seems to work best is a heavy chain with big links, so the dog is forced to eat under and around it, not a ball as is commonly recommended).
3) Owners of anxious and fearful dogs should consider behavior modification. Drug therapy may be warranted in serious cases.
4) Feed several small meals per day instead of one large meal.
5) Do not elevate the food bowl.
The greatest value of this study is that it is prospective in nature, meaning all the information about the dogs was collected before anyone knew which dogs would develop bloat and which would not. This way owners and researchers were unbiased in how the information was collected.
Information compiled from the personal experience of losing Ben, the attending Vet and a Veterinarian friend's comments on Bloat and from the Journal of the American Animal Hospital Association 1997 & 1998 and the Journal of the American Veterinary Medical Association 1994.