The Alberta (Canada) Agriculture and Forestry department encourages livestock producers to plant annual ryegrass as a forage crop. Here’s a link to the entire article. 

In essence, they say that ryegrass and other annual crops provide flexible feed sources for livestock. Ryegrass has the advantage of being a quick crop to grow to extend grazing in the fall and/or spring.  It can be used as emergency forage if alfalfa is killed during the winter. It establishes quickly and produces a lot of forage in a short amount of time.Of course, excess can also be stockpiled as feed.

When managed intensively, ryegrass can be very productive, the article says. It goes on to say: The fact that the crop has little or no dormancy makes it an ideal fall pasture as it continues to grow and maintain its quality well into the fall, making them useful in extending the grazing season.

In areas with very cold winters, annual ryegrass will often be eliminated by winter weather. But if it does winter over, it grows back quickly in the spring for continued use by livestock. But if the crop will be replaced by corn, for example, eliminating the annual ryegrass is imperative. Click here to review the proper management of annual ryegrass in the spring.