black hair; black fur
Refers to black hair or fur of animals, or sometimes human hair in descriptive contexts.
That dog has beautiful black fur.
black-haired horse
Specifically a horse with a black coat; used in equestrian or farming contexts.
That black-haired horse is fast.
She walked with her black hair flowing.
Compound of 黒 (くろ, 'black') + 毛 (け, 'hair/fur'), with rendaku voicing of け to げ.