Rye, wheat, and oats are cereal grains, not grasses. Timothy, Perenial Rye, fescue would be considered examples of grasses. The Cereal grains are annuals and the leaves are very high in carbohydrates compared to the grasses. They are very digestable by deer before they start to head out. They are a preferred food in the fall in my area, we plant in September. If you examine the stomach of a deer thats been feeding in a rye feild, you'll notice its just a bright green slurry. Conversely, occasionally you'll find small amounts of grasses mixed in the stomach as well. These plants look almost like they the were when ingested. Most grasses are very high in cellulous, low in carbohydrates.

I maintain that deer rarely eat grasses on purpose. Even when they have the right micro-organisms to aid in digestion, the process takes a very long time in a deer's digestive system. I do think that deer "sample" all kinds of possible foods for several reasons. Deer are very adaptable when it comes to food sources. However, they still need at least 2 weeks to develop the right bacteria in their stomach for new foods. By sampling different food sources occasionally, they speed this process up should they have to switch food sources for some reason.

On a similar note, we provide clover plots year round, annuals for the fall and spring and corn for the fall and winter. There is enough forage available for our herd that they shouldn't need for other foods. Yet they still browse on saplings (alot) and will all but switch over when mast like apples or beechnuts fall. Deer do not like to put all there eggs in one basket - thats why several food types/and plenty of natural browse are important.

This year after season, I video taped some deer from a treestand in a mature Hemlock/Beech woods as they worked toward the standing corn feild. We had about 1 ft of snow. It was very interesting as two deer came through, pawing for ferns under the snow. As the found them they would nip them close to the ground, and eat the foot long ferns as they watched ahead of them. They probably ate 20 each as I video taped them. I have no idea how digestable they are, also I never see them selecting ferns in the fall like this.