For about a month now I've been supplementing pasture with hay for my Angus/ Hereford herd. This evening I put out 2 bales with the Angus going after the first and the herefords the second. After about 10 minutes one of the Herefords stepped away from the trough and spit up about 3-4 times. A few minutes later a second Hereford did the same, followed by an Angus. They seems OK otherwise and shortly after went back to feeding. Is this simply a case of "rumen overload" or something I should be concerned about?