It's definitely not grass because he is in a grass paddock and never coughs eating the grass. He does it once or twice when he is eating a flake of hay. The hay is 1st cutting. I think it is the dust or the scratchiness on his throat. I guess the last person he was with for a trial tried soaking the hay but apparently it didn't make that much of a difference but one would think that you would have to see a difference in longer than 2 weeks. I will talk to the vet when she comes next week.