Here is one article I found on it: Experts: Contamination from GM Alfalfa Certain
I don't regularly feed alfalfa to my horses but I have fed orchard grass - alfalfa mix in the past and I know people who feed alfalfa pellets. For some reason this worries me more than other GM products that are found in horse feed such as corn and sugar beets (beet pulp).
Has anybody heard about affects that GM products might have on horses? What is your opinion on this? Right now I'm not so sure what to think about it.