Genesis 30:37-39

37Then Jacob 1took fresh rods of poplar, almond, and plane trees, and peeled white stripes in them, exposing the white that was 2in the rods.

38He set the rods which he had peeled in front of the flocks in the drinking troughs, that is, in the watering channels where the flocks came to drink; and they mated when they came to drink.

39So the flocks mated by the rods, and the flocks delivered striped, speckled, and spotted offspring.