Genesis 30:38; Genesis 30:41

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

41 Moreover, whenever the stronger of the flock were mating, Jacob would place the rods in the sight of the flock in the gutters, so that they might mate by the rods;