Bran has a lot of fibre and the human digestive system doesn't have the enzyme that digests fibre, but there are bacteria living in the large intestine that can digest fibre. As they digest, they release gas
The large intestine function is digest to your food
Intestine
intestine
The large intestines function is to digest your food.
They have a small intestine because dogs are carnivores (they only eat meat). An animal with a large intestine digests fibre as well, which a dog does not eat, and therefore does not need a large intestine!
So it can properly digest and excrete food.
intestine
small intestine
* Part of digestive system * intestines * absorb (small=nutrients large=water)
Bacteria
the large intestine absorbs water and starts to digest it and goes through the rectum