Could you take a sample of it to your local Cooperative Extension office to see if they can have it tested? Odds are, if it is the hay, you aren't the only person that bought it.
My hay was bermuda/mixed grass horse hay. It was fertilized. Alfalfa isn't available around here. I wish it was. Maybe there is a fertilizer or something that is being widely used on hay and is causing problems. I usually buy from individuals since I need hay for my horses and goats, but this time I was in a tight and got it from the feed store. The last baby died with in 24 hours of eating it! I'll check the other forum too!