This occurs due to magnesium deficiency.

Cows are agitated and jittery. They chew and sometimes froth at the mouth. This one was chewing the bars on the yard. They also often will be starry eyed and not focus on you. They will sometimes charge you.

Treat with a bag of Magnesium Sulphate.

ONLY EVER TREAT UNDER THE SKIN

TREATING IN THE VEIN WILL KILL THE COW.