He put those sticks in the animal's water tanks. When the animals came to drink from those tanks, they mated and when the baby animals were born they had stripes and spots in their fur. In the mating season, Jacob put the boy animals that were white in with his spotty and dark coloured animals. The animals mated, and when the babies were born they were all spotty and dark coloured. Then Jacob took all of the spotted and dark coloured animals and put them in his own paddock. He made sure that his animals stayed away from Laban's animals. This is how Jacob made his mob of animals grow bigger in number.