Well, not really magnetic, but they do tend to align themselves to the Earth’s magnetic field. A scientist has researched the alignment of herds of cows using images from Google Earth. His results show that herds of cattle and deer will, when standing still, all align themselves north-south. However, disruptions of the local magnetic field, such as those caused by powerlines, upset their senses and they tend to point in random directions. This effect becomes less pronounced the further away from the powerlines the cattle are.