In the past, I haven't had an issue with my other goat herds. New goat herd and they are eating Bracken Fern and Horsetail. My Vet says it's toxic to them. I have over 4 acres of pasture/blackberries/browse, and 9 goats (2 adult Alpines, 2 Alpine kids, and 5 mini/cross). I'm in western WA state and it's hard to contain/eradicate...suggestions?