Genesis 30:37-39

Then Jacob took some fresh branches from poplar, almond, and plane trees and peeled off strips of bark, making white streaks on them. Then he placed these peeled branches in the watering troughs where the flocks came to drink, for that was where they mated. And when they mated in front of the white-streaked branches, they gave birth to young that were streaked, speckled, and spotted.