Write the next sentence in this paragraph:

How to tell a horse's age by its teeth
Look a the color of the horse's teeth.
The color of a horse's teeth provide a general clue as to horse's age. The milk teeth are white, and the permanent teeth (which erupt at 2 to 5 years of age) that replace them are cream-yellow.
With increasing age they turn brown (20 years plus). Examine the shape of the chewing surface.