What is the condition called when a ruminant animal has a distended stomach filled with methane gas?

The condition described in the question is known as being "bloated," which occurs when a ruminant animal experiences an accumulation of gas in its stomach—specifically, methane. This is often due to an excess of fermentation occurring in the rumen, which is the first compartment of their stomach system. Ruminants, such as cows and sheep, produce methane as a natural byproduct of digestion, especially when they consume fibrous plant material. When too much gas builds up and the animal is unable to expel it, it leads to distension of the abdomen, causing discomfort and potentially serious health issues.

In contrast, gastritis refers to inflammation of the stomach lining, while enteritis involves inflammation of the intestines. Dehydration is a condition that results from excessive loss of fluids and does not specifically relate to gas accumulation in the stomach. Therefore, the correct term for the condition when a ruminant has a stomach distended with methane gas is indeed "bloated."