My six yer old dashound has a bowel problem he is unable to pass his poo his bowel gets filled and looks like a tennis ball he tries four or five times and nothing only a small piece,and not breaking off,he has had two surgeries the second one a complete failure he has had x rays blood work laxatives and medication the vet says to put him down

Have you only seen one vet? You didn't give us the diagnosis. I'd get a second opinion or even a third before I'd put my dog down.