All cows have been vaccinated prior to calving 60 and 30 days-calves are exhibiting s/s of enterotoxemia-- diarrhea/scours, look fine one morning and check the following day and the calf is half dead-- all have bloody scours- most are 1-4 days old. One had same symptoms - seemed to act like muscles were affected- kicked at it to get it moving and it flipped onto it's back and died. We experienced same thing last year at the same time of year-- Nov 1-15. Cows are on good pasture- protein licks, salt readily available, etc.... Anyone know what this is and how to stop?