which direction is north-south.
Even if that's correct, may have more to do with the sun's travel across the sky than anything else. Also the latitude might make a difference? More sun on the side means warmer cows in the northern climes, less sun is cooler cows in the equatorial regions. Maybe equatorial cows graze to the west in the morning, and then when the sun gets in their eyes graze to the east in the evening.