Do you know for a fact that the johnsongrass will cause problems for your cattle?

THere are dairy farmers in this area who have gone to intensive grazing systems.  They have found that johnsongrass will not stand the intensive grazing. In fact, one guy in particular who like to plant some johnsongrass to graze... if he could. (Of course, he can't and won't.....  because it is considered a noxious weed and is illegal to plant it here.)

The point(s) is/are:

1) is it really harmful to your cattle?

2) maybe managing it with a cutterbar is an option.