If you had any common sense, you would know that you need to take your dog to the Vet to find out why it's pooping blood, and after a Vet diagnosis the problem then hopefully this medical issue can be fixed.
Blood from either end isn't good. I'd need more information, age of the dog, how often the need for a BM, bright red or dark red, other symptoms for eg.
Right now, the only answer is to find a vet. Don't feed any more food until you have. And clearly if the bleeding is copious, you need a vet as a matter or urgency.