In Chapter Three of Animal Farm, Jessie and Bluebell give birth to "nine sturdy puppies" and, after they are weaned, they are taken away by Napoleon. He tells Jessie and Bluebell that he has done this for the purpose of educating them, but, in fact, Napoleon is training the puppies to be his personal bodyguards. This explains why the puppies are kept in virtual isolation, in a loft above the harness room which is accessible only by a ladder.
This act is significant because it marks the beginning of Napoleon's reign as the farm's absolute leader. Once he has trained the puppies, he uses them to exert his will and to eliminate any opposition. We see this in Chapter Five when Napoleon uses extreme violence to run Snowball off the farm after a heated debate over the windmill.
Napoleon was taking it upon himself to correctly educate the young puppies about animalism. We find out later, of course, that he is really turning them into his own personal guards.