Mast is nuts. Specifically, it is the nuts from trees. Browse on the other hand is twigs and branches that deer cklip off with their teeth.

Mast crops, acorns mainly, make up almost 80% of the deers diet during years of a heay mast crop. Different oak trees have different cycles and they may have a crop of acorns every year, every other year, or every third year. The deer respond by feeding on what is available in order of preference. The favorite is the white-oak the least favorite in my estimation is the rock oak, those big round ones. They have more tanic acic making them bitter. Go ahead, try one! During poor years or years with low mast crops, finding a tree that is producing is a blesssing. That tree will get hit hard because deer want those acorns. The nuts are almost all fat.

Greg