Born after an average of 63 days of gestation, puppies emerge in an amnion that is bitten off and eaten by the mother dog. Puppies begin to nurse almost immediately. If the litter exceeds six puppies, particularly if one or more are obvious runts, human intervention in hand-feeding the stronger puppies is necessary to ensure that the runts get proper nourishment and attention from the mother. As they reach one month of age, puppies are gradually weaned and begin to eat solid food. The mother may regurgitate partially digested food for the puppies or might let them eat some of her solid food. The mother usually refuses to nurse at this stage, though she might let them occasionally nurse for comfort.
If your pup barks: Some dogs have the habit of barking at other dogs while on a walk. Oftentimes, this behavior comes as a result of lack of exercise. Make sure your dog gets the proper amount of mental and physical stimulation for his age and breed. If this is still a problem, use the same process as you would if your dog is lunging, as described above — create distance and offer treats before he starts to bark, so every time he sees a dog he gets used to turning his attention to you.
Help him relax when he comes home. When your puppy gets home, give him a warm hot water bottle and put a ticking clock near his sleeping area. This imitates the heat and heartbeat of his litter mates and will soothe him in his new environment. This may be even more important for a new dog from a busy, loud shelter who's had a rough time early on. Whatever you can do to help him get comfortable in his new home will be good for both of you.
Just as a child needs a caring parent; an athletic team needs a coach; your puppy needs a leader and a clear social hierarchy. If you do not take up the role of leader, your dog will; and you will end up with an unruly, disobedient dog. Many people try to win their new puppy's love by letting the puppy always have its way. Buckets of affection is a wonderful thing for most puppies, but it must be tempered with respect.