Genesis 30:37-42

But Jacob got fresh branches from poplar, almond, and plane trees and peeled the bark, leaving white stripes on them. He stuck the peeled branches in front of the watering troughs where the flocks came to drink. When the flocks were in heat, they came to drink and mated in front of the streaked branches. Then they gave birth to young that were streaked or spotted or speckled. Jacob placed the ewes before the dark-colored animals of Laban. That way he got distinctive flocks for himself which he didn’t mix with Laban’s flocks. And when the sturdier animals were mating, Jacob placed branches at the troughs in view of the animals so that they mated in front of the branches. But he wouldn’t set up the branches before the feebler animals. That way the feeble animals went to Laban and the sturdy ones to Jacob.