Mental Disorders/Disabilities in chickens?

[Flax]

Has there ever been any studies done or have you noticed any chickens acting just a little bit 'off'? For example... I think my Rooster has problems. When he was a baby he had rickets and needed extra vitamins when he got older though he has tried to mate with geese(there's a fence separating them now) only 1 out of my 3 hens 'like' him and he pecks at his water. He doesn't dip his beak and pull his head back like the other chickens. He pecks at it like it was food. He is now almost 2 y/o so I don't think he'll change?

He is extremely sweet to me though. Lets me pick him up whenever and just sits still in my arms till I get tired of holding him.

Also do you think domesticating them and mass breeding could've brought upon these problems? I wonder how different the chickens today are in behavior to their wild relatives.


Might be some interesting discussion!