Genesis 30:37-39

37But Jacob took fresh white poplar, almond, and plane tree branches, peeled away white stripped sections on them, exposing the white of the branches.

38Then he set the branches he had peeled in front of the flocks in the drinking troughs and watering channels where the flocks come to drink. Since they were in heat when they came to drink,

39the flocks mated near the branches, and the flocks gave birth to striped, spotted and colorful ones.