Genesis 30:37-39

37Then Jacob took fresh-cut branches of poplar, almond, and plane trees and peeled the bark on them in strips of white, uncovering the white which was on the branches.

38He placed the peeled branches in the troughs directly in front of the flocks, at the watering places where the flocks came to drink. When they were in heat and came to drink,

39they mated in front of the branches. Then they gave birth to young that were striped, speckled, or spotted.