Do you reckon that it was just boredom? I mean, I've been known to eat stuff that I wouldn't ordinarily eat when I didn't have anything else, even though I wasn't really hungry. Maybe their salt block was kinda like their potato chips. ;o)
That could be too. There's certainly not any pasture growing out there, and though I've been feeding them hay on the ground during the day, they aren't exactly thrilled by the hay we've got available right now.