Symptoms of  bloat or torsion include extreme restlessness, salivation, successful or unsuccessful vomiting, and progressive abdominal swelling. A dog beginning to bloat may seem larger around the last ribs before abdominal swelling is noticed. All of these symptoms occur in a short time span, quickly leading to severe shock and death in as few as six hours from the onset of symptoms.  Irreparable damage to internal organs occurs quickly, due to shock,  which severely complicates treatment in animals caught only a few hours after onset.

The importance of immediate veterinary intervention can not be stressed enough. Immediate decompression of the stomach or surgery,  in the case of torsion,  is necessary to save the dog's life.

Torsion occurs, when the stomach becomes increasingly swollen, during bloat, and rotates, causing all circulation to be lost to the stomach and other vital organs. It has also been speculated that torsion can also be caused by loose abdominal muscles, when a dog is exercised immediately after a large meal.  Both bloat and torsion are equally dangerous, as both will lead to shock and death if not treated as immediately as possible.
 
Research has been done to study possible causes of bloat and torsion in dogs. Most of the research has been inconclusive as to the actual cause of bloat. A few factors were isolated, and later discounted as a possible cause of bloat, such as the dog being fed only one large meal of dry food daily,  the dog was habitually exercised after meals, or the dog was allowed to consume large amounts of water after a large meal of dry food.

Some causes have not been discounted, such as sudden changes in diet, recent de-worming, vaccinations, or antibiotics, and exposure to high stress situations. Many dogs that develop bloat have been described as having a nervous, high strung, very sensitive or easily stressed personality.

Each of the above factors can result in destruction of probiotic (friendly) bacteria in the digestive system. These bacteria are essential in maintaining an acidic pH in the digestive system, and they also are very important to carbohydrate digestion. Carbohydrates quickly ferment in the digestive system when they are not properly digested. Many cases that were documented showed that the dog was fed a low protein diet, (under 30%)  that contained a large amount of grains and carbohydrates. It is very possible that some animals may have an inherited tendency to have poor carbohydrate digestion.

According to Joseph Pizzorno, N.D. , who is the founding president of the renowned Bastyr University, in his book Total Wellness, abdominal bloating and gas is caused by "Undigested carbohydrates resulting in excess gas production by bacteria".

More recently, some animal health nutritionists have implicated Brewer's Yeast (also known as Saccharomyces Cerevisiae) or other yeast products as a contributing  factor to bloat. This is understandable, because this ingredient would increase gas and fermentation in the stomach, especially in the presence of poorly digested carbohydrates.

According to a report on studies of bloat done at Purdue University, bloat cases have risen 1500% in the thirty year period between 1964 and 1994.

Their report dated January, 1997 states: "This increase is unlikely to reflect changing diagnostic criteria or disease recognition. The increasing frequency of GDV starting about 1969 affected most of the large and giant dog breeds. Therefore, it is also unlikely to be caused by genetic factors. However, this apparent epidemic of GDV could be explained by introduction of one or more novel environmental factors such as a new ingredient in dry dog foods or a change in the manufacturing processes. It might also be related to changes in canine vaccines or their pattern of use, e.g., multivalent vaccines."
 
A pre-disposition to this condition has been observed in animals that have low pancreatic function, especially in animals that produce low levels of Trypsin, which is an important protein digesting enzyme.

A normal test range for Trypsin in dogs, is between 5.0 to 35.0 ,  if a dog is below the normal range , veterinarians prescribe pancreatic enzymes to maintain the dog's health and weight.  Many of the dogs in the low normal range might never be tested if they do not have any digestive symptoms, such as weight loss or diarrhea, although these dogs would require more than an average amount of food to maintain their weight.

Animals that are fed higher protein diets, or are given meat with their regular meals, have higher Trypsin levels than animals that are fed low protein diets. It has been proven that increasing protein in the diet also increases Trypsin levels in the blood.

Higher Trypsin levels contribute to a healthier pH level in the digestive system, which is important in maintaining a healthy balance of microflora, which require a more acidic environment to survive. Factors, such as stress, de-worming, or antibiotics, are known to destroy beneficial bacteria (microflora)  in the digestive system.
 
Prevention lies in maintaining a healthy digestive system.  Bloat and torsion is practically unheard of in dogs that consume a high protein, raw meat based diet, that  includes minimal amounts of grain and carbohydrate. (less than 25% carbohydrate) If you own a dog that has previously bloated I would recommend completely eliminating grains and carbohydrates from its diet.

A dog should consume a minimum of 1.75 grams of protein for every pound of body weight daily. Diets containing gluten meals or soybeans should not be fed, because they have been shown to contain anti-Trypsin factors that reduce blood Trypsin levels. Wheat has also been shown to contain anti-Trypsin factors.

Additionally, dogs should receive a probiotic supplement daily that includes more than one strain of beneficial bacteria, although probiotics alone have not been shown to prevent bloat.

Fiber also helps to maintain a healthy digestive system, and encourages the growth of beneficial bacteria. Studies have not been done to determine if the source of fiber has any relevance in bloat cases, although some articles report an increased incidence in dogs fed a diet that included beet pulp or alfalfa meal as the fiber source.

Fiber levels in the diet should be maintained at a level that encourages normal  intestinal motility.  A normal diet should contain at least 2.5 grams of fiber for every 15 lbs. (6.8 kg.) of body weight per day. In a commercial food, this would represent an analysis of  3.00 % crude fiber.

If you own a dog with a family history of bloat or torsion it would be very worthwhile to feed it a diet that contains at least 75% raw meat, with a fiber source such as bran, along with a broad spectrum, high potency probiotic supplement. (I recommend a product available at health food stores called PB-8) Some breeders of large dogs like to supplement with a tablespoon of apple cider vinegar in each meal to promote acidity in the stomach. Sources of additional carbohydrates or yeast, such as most commercial dog biscuits, should be avoided.