What is this?

[Pinklemary]

Old Dorking hen having difficulties, she is melancholy and is producing very loose poo. Including stringy red stuff that looks very odd, any advice?

 

[Eggcessive]

Welcome to BYC. That looks like blood, and I would go get some Corid today from a feed store to start treating her and the others for possible coccidiosis. Symptoms are lethargy, standing hunched or puffed up, not eating, and runny poops with mucus or blood. Corid dosage is 2 tsp of the liquid, or 1 1/2 tsp of the powder per gallon of water for 5 days. It is safe for all to drink, and change water daily. Here is a good link about coccidiosis:
http://www.the-chicken-chick.com/2012/12/coccidiosis-what-backyard-chicken.html

 

[Pinklemary]

We've read that hens can shed their intestinal linings and I wonder if it could be that, I've seen coccidiosis before and this looks very different.