Cattle do not suffer from cardiovascular disease like people do - most strokes are related to atherosclerosis (hardening of the arteries) which results in narrowing artery and decreased blood to the brain and eventually no blood to that part of the brain and a stroke. That is the most common cause of stroke in people - there are also hemorrhagic strokes (ie bleeding into the brain like a ruptured blood vessel) and clots that break off from somewhere (say the left atrium) and go to the brain.
Cattle don't get atherosclerosis, and although I suspect they could have abnormal blood vessels in the brain that would leak or bleed it sure isn't common if it occurs at all. The most common heart disease of adult cattle would be related to hardware, but this would not likely lead to blood clots to the brain.
All that said (and perhaps more than you ever wanted to know) cattle do have (or get) a variety of neurological diseases which could mimic what one might think a cow with a stroke would be like. Hope that helps ...
