Genesis 30:40-42

30:40 Jacob removed these lambs, but he made the rest of the flock face the streaked and completely dark-colored animals in Laban’s flock. So he made separate flocks for himself and did not mix them with Laban’s flocks. 30:41 When the stronger females were in heat, Jacob would set up the branches in the troughs in front of the flock, so they would mate near the branches. 30:42 But if the animals were weaker, he did not set the branches there. So the weaker animals ended up belonging to Laban and the stronger animals to Jacob.