Nasolabial plane

The nasolabial plane is the most rostral surface of the external nose in cattle, also called the muzzle. It is hairless, pigmented, and divided by the philtrum, which extends along the midline. Its surface is subdivided into small polygonal areas by grooves, the arrangement of which remains unchanged throughout life and is characteristic of each individual.

In carnivores, sheep, and goats, the top of the nose is called the nasal plane. In pigs, it is the rostral plane or snout.