Goats and sheep do consume leafy spurge and all manner of undesirable plants. The goats I assume were angoras, given the time period you stated, and they worked extremely well when you could keep them in. I worked on leafy spurge at NDSU from 1986 til 1991. Sheep and goats also ate Wormwood, Canada Thistle, bindweed, dandelions, and many more weeds. Goats are a bitch to keep in though. Most folks claim that if water can get through a fence so can a goat. Sheep are much more comfortable with confinement. Many sheep flocks are kept in with only a single strand of electric wire. I'm actually quite surprised there are not more flerds (sheep flock and a cow herd) in ND. They compliment each other quite well with the sheep eating what the cattle tend to avoid which keeps the pastures in much better shape IMO. There are many other advantages to having both ruminants in the same pasture, but for some reason running them together hasn't caught on. Maybe someone in the peanut gallery can shed some more light on the subject.