How can you remove dark stains on Bruce hardwood floors caused by dog

https://housewifehowtos.com/clean/how-to-clean-pet-stains-on-laminate-floors/

You would have to sand off or use stripper to remove the finish, then use wood bleach to lighten the stain, and then possibly stain to match floor, and finally top coat with same finish i.e. matt, satin, or semi-gloss. Start crate training your dog and have dog checked out by vet.

dark urine-related stains are usually on oak... oak is sensitive to ammonia- which is the product of decaying urine... That stain is TOUGH to remove!

Try: Remove the top finish - then sand to expose fresh wood- it too may be stained. Use wood bleach... repeat if the stain persists - (you many never get it All) ... resand to a smooth surface and refinish.

I Just saw Sharon's answer- and must say our approaches are too similar to be random!

I would also suggest sanding it down and then restaining the floor.