Coughing?

[shortlilcutie]

I'm with my piggies visiting at my parents house for the next week and a half. I took my boys outside to roam in the grass. I was sitting with them and they stayed close to me because they had never been out in a big back yard before. The ate grass and had some fun, but one of my boys coughed a couple times. I've never heard him cough before, and he hasn't coughed again since. The grass hasn't been sprayed, so that's not a worry. Any idea why this happened? Just from the air maybe? TIA!