Genesis 30:37-39

So Jacob cut green branches from poplar, almond, and plane trees and peeled off some of the bark so that the branches had white stripes on them. He put the branches in front of the flocks at the watering places. When the animals came to drink, they also mated there, so the flocks mated in front of the branches. Then the young that were born were streaked, speckled, or spotted.