The colon produces mucous when it is irritated/inflammed.
The most common cause in young dogs is worms particularly whipworm. Have your vet run a fecal and/or give him a dewormer that kills whipworm as well as the other species (round, hook, tape). Coccidia and Giardia are other possible intestinal infections that could cause mucous in the stool.
The mucous can look slimy or can look stringy. Large numbers of worms can alse look stringy.
I did understand, but thanks for restating it because I thought of something else.
Parasites are still on the list.
Does your pup eat things like parts of toys, socks, plastic bags, etc. These can look very funny when they emerge at the far end and are often covered with mucous.
did you try picking apart the blob?
Chicken bones could cause irritation as they pass out, but in general do not.
Let me know what you find when you pick it apart.... if you find it.
Dogs don't usually sneeze out the quantity of mucous you described. The last part of the intestine can prolapse (hang out), but they don't poop intestines.
I've seen some pretty scary stuff come out of one of my boys who likes to eat the smaller stuffed toys...whole.
I'm glad I could help. Have a nice day!