"The toenail is composed of two major parts – the quick, the blood supply and nerve that nourish the nail, and the horn-like nail tself. Just like human nails, dogs do not have any feeling in the nail itself, but the quick contains a nerve that transmits sensations back to the brain. When trimming the nail, it is important to stay far enough from the quick to avoid causing pain or drawing blood." ( https://caringhandsvet.com/trim-dog-nails/)