My goats also love pampas grass and the many (many) massive ornamental grasses planted by the previous owner. I had noticed for the last few years that they were self-seeding into multiple clumps all round the garden and, pre-goats, decided to get my husband to zap them with weedkiller. Now I'm glad I didn't because they grow and re-grow from cropping armfuls all summer and the goats wolf them down.
In the past I used to burn the stems when I chopped them back and they gave off a burnt-sugar smell so I imagine that is why the goats like them so much: mini-sugar cane.
I'm also planting tiny self-sown goat willows all round the edge of my garden because the girls love every part of it. When I walk my dogs round local lanes there are lots of 6" high seedlings in the verges which I pull out and all I need to do is make a tiny hole with a garden cane and stuff them in when I get home. Last week I found almost a whole large goat willow that someone had dumped illegally - so I very kindly tidied it up...