I have a 10.5 week yorkipoo. I got him when he was 8.5 weeks old and weighed 1lb 6oz, now he only weighs 1lb 4oz at 10.5 weeks (
lost weight 
). The very first night I brought him home he had stool with
mucus and
blood on it. I brought him to the vet immediately the next day and they tested him for
parasites/worms and they came back
negative. Vet said it may be from
stress colitis and it should improve with time. I no longer find blood in his stool which is good but at least once a day he has a stool with mucus. Sometimes it's a little mucus on the end or sometimes it's a puddle of mucus with a little bit of poop in it. So of course, I called the vet and they gave me a
probiotic to give him. He only ingested it one time and refuses to eat anymore of it (powder). I sprinkled it on his food in a bowl but he only likes to eat his food when it is scattered on the ground. I'm not sure how else to give him the probiotic. Does anyone have any suggestions on how to feed it to him or what this mucus may be caused from? It's very stressful and nerve wracking not knowing what's going on in my little guy. Is there anything else I can do for him? Are there more tests that should be/could be done?