Mulitflora rose (Rosa multiflora) - Cows trained to eat Canada thistle, leafy spurge and spotted knapweed in Montana chose to eat this in pasture as well.

This plant was introduced from Japan as rootstock for ornamental roses. In the 1930s the U.S. Soil Conservation Service promoted it for erosion control and living fences and in the 1960s the Virginia Highway Department planted it in interstate medians to reduce headlightglare and provide a crash barrier. One multiflora rose can produce as many as 500,000 seeds per year and seeds can remain viable in the soil for 10 to 20 years.

Toxins: I have found none listed, and I have found no information indicating problems with animals eating this plant.   However, since all plants contain toxins I would be sure that animals have a variety of forages to mix with this plant.

Grazing Prescription: According to the National Park Service, frequent, repeated cutting or mowing at the rate of three to six times per growing season, for two to four years, has been shown to be effective in achieving high mortality of multiflora rose. So, if eradication is you goal, put your four-legged mowers to work on your multiflora rose at that rate. If that's more fencing and labor than you care to invest, think of it as forage.

For more info, check out this NPS fact sheet