weight gain and red blood in stool

Question
We have a 6 yr old boxer male named baxter. over the last couple of months he has put on 10+ lbs. yesterday blood (red) was noticed in his stool. it was also present today. the only abnormalities observed before with his stool was Thursday he had a touch of diariah. the bloody stool was noticed by a friend of his (and ours). as we were out of town for the weekend. we just received the info during a call to check on him.problem now is tomorrow is labor day and i don't expect to find a vet available. however we are very worried as he is one of our kids.  

Answer
In the meantime waiting to get him to a vet ASAP-- give him Pediolyte clear. This is for children during diarrhea, to keep them from dehydryating. A generic Pediolyte is okay.

Also, give him plain whole yogurt and cut back on dog food.

If you cannot see your normal vet Tuesday- get him to an emergency bet hospital. Something is wrong when blood and diarrhea is present.