Hey Karen -
Really nice people. I actually contacted them and they confirmed they do use silage. I too made some cheese with their milk, but it's been a long time now and I can't recall the type of cheese, or what I experienced using it. I do know nothing weird came from it, as I think I would have remembered that.
With silage my concern is late blowing, clostridium. Alp can confirm this but Swiss alpines prohibit its use something like at least 6 weeks before beginning the pasture-based alpine production season, and the cheese I model from, Beaufort, prohibits the use of silage at any time.