My Dad has a 12 wk old Brahma cockerel who is not walking, poop is greenish but is eating and drinking like normal. He said it uses its wings to move around. The cockerel let's Dad move it's legs and doesn't act as if it is in pain but can not stand up or walk. Is this Mariks disease? Any hope or should the bird be culled? He has already put it in a separate pen but was showing symptoms before he did that. Thanks for the help and info!