Treats and chews are given to dogs for a variety of reasons. Chews are used to occupy the dog and help clean its teeth. Treats may have the same cleaning function, as well as provide some nutritional value.
Treats and chews can be made from a variety of materials. For example, the products can be made of processed, dried animal skin, such as rawhide (untanned cattle skin) or pigskin. The skin is processed by removing hair and cleaning it of fat and muscle. The skin is then manipulated into the desired shape, such as by folding or rolling, and then dried.
In the prior art, treats and chews can be made of materials other than hide. For example, the products can be made of plastic, rubber, etc. 
Even when dogs chew on treats and chews, their breath may have an unpleasant odor and their teeth may not be cleaned. For example, on a rawhide chew, a dog has a hard time piercing the tough dried skin with its teeth. Thus, the teeth are not cleaned and the dog continues to have bad breath.