Gastric Dilitation-Volvulous (GDV)

Bloat or GDV is a devastating killer of dogs  and it is the greatest killer of the Greater Swiss Mountain Dog.

Mostly, GDV  occurs in deep chested breeds, such as the GSMD and requires immediate veterinary care.
Unfortunately, even with the speediest care, many dogs do not survive. 

Bloat can occur with or without torsion of the stomach and/or spleen, just as torsion can occur with or without bloat. When abnormal amounts of air, food, fluids get into the stomach, you have the right conditions for bloat. It can be caused by wolfing down too much water, too much food too fast, exercise after eating, stress, or conditions too numerous to mention and some unknown as well. 
Symptoms can be distended abdomen, excessive  salivating, depression, lethargy - 
There are so many symptoms that you would just have to know your dog and know that something was not right. 

When Bloat occurs it cuts off the esophagus and the blood supply to the heart is lessened causing low blood pressure as well as other cardiac problems. This causes the dog to go into shock. Organ damage can occur as well and the stomach 
may rupture causing peritonitis to set in. This can also affect the stomach and spleen and cause torsion.

If not treated immediatly, the dog will die. 

I would urge all Swissy owners to acquaint their veterinarians and emergency care facilities that you have a GSMD

and this  is a breed that is very prone to bloat and torsion. 

In the Purdue Bloat Study, they state that though there are ethical issues that need to be considered by dog breeders and  veterinarians, any dog that is prone to GDV should have an elective gastropexy (stomach tack).

Gastropexy will not prevent bloat, but will prevent the torsion that usually occurs with the bloat, and the dogs chances of survival improve greatly.