We had the same thing happen in Feb to a 10 day old hfr calf...not sure why, but she was picking at some leafy hay in the round bale feeder. I was told by our vet not to tube one that young, since they don't have a functioning rumen at that age, and things are actually routed a little differently in their stomach till they get older. We gave her 2 cups of Milk of Magnesia to act as a laxative in case she was bound up. I also put about 1 cc of therabloat in it too. Seemed to work, as she was better the next day, although a little loose behind which was expected. Good luck!