Whenever the stronger females were in heat, Jacob would place the branches in the troughs in front of the animals so they would mate near the branches
NIV
And whenever the stronger animals were breeding, Jacob laid the rods in the watering troughs before the eyes of the flock, that they might breed and conceive among the rods.
AMP
And it came to pass, whensoever the stronger cattle did conceive, that Jacob laid the rods before the eyes of the cattle in the gutters, that they might conceive among the rods.
KJV