You could talk with other farms and see what mix they are using. We are in Mi and have been using a mixture of Orchard/Brome/Timothy. The Alpacas seem to be doing very well on it and love the mix. I know many say Orchard only but I feel that a variety offers more.
"quote from another site"
"Alpacas need variety as much, if not more so, than other herbivores. Feeding them one type of pasture and single species hays is a recipe for disaster over the long run, in terms of the potential to create nutritional deficiencies. No one forage has everything an alpaca needs."
We have used the Norm Evan's Field Manual. It has the information someone would need to determine the seed to use. We gave the manual to a local farmer and he planted it and was supposed to harvest it for us. Unfortunately, this year our area was hit with a devastating insect (called Armyworm) that wiped out our entire field before we knew what was happening. We will be planting it again next year for hopefully a better outcome.