You may find the sheep will decide whether it's edible or not! My lot have been very choosy in the past and I tried 4 or 5 sources before find some they would eat. Once found though, I've been able to use the same "brand" every year since.
While I was struggling to find a hay they would eat, The advice I got was 'if they're hungry enough, they will eat it". But I'm not sure that's true, and I wasn't prepared to stand by and watch them get thinner and thinner!