1.   Efforts to prevent the disease in cows so far have centered on eliminating animal feed that is laced with infected animal parts.

2.   To date, efforts to prevent the disease in cows have centered on eliminating animal feed that contains infected animal parts.

3.   To date, efforts to prevent the illness in cows have centered on eliminating animal feed that contains infected animal parts.

4.   While many questions remain about mad cow disease, efforts to prevent the disease in cows have centered on eliminating animal feed that contains infected animal parts.