Personally, I'm a firm believer in creating a good
herbal ley pasture. Not only does it give variety to the diet, it also provides the livestock with their own 'medicine chest'. They will 'self medicate' their way through almost any health issue (including worms).
To be most effective, it needs four basic components:
* Warm season grasses
* Cool season grasses
* Warm season broad leaves
* Cool season broad leaves
Here is a good read on the subject. You will undoubtedly need to select species that do well in your location.
http://www.acresusa.com/toolbox/reprints/Oct03_Forage.pdf
Sugar beets, or mangles would provide a good source of feed for much of the winter.