7 y/o lab with our new puppy

Question
Hi. I have a seven year old chocolate lab named Doctor Dog. He was fixed about a year ago. He spent ages 1-3 with another dog (a total non-alpha sheltie) and they got along fine. Other than that he really has no experience with other dogs and seems aggressive around them. My wife and I just got a 2 month old sheppard/lab mix and he is so tiny and cute. We can't keep them even close to each other because Doctor Dog looks like he want to kill/hunt the puppy. The two times we got them close together, Doctor nipped at the puppy and the puppy yelped. I made sure to let Doctor Dog know that he was bad and maintained my leader of the pack attitude, which he has always accepted. Doctor Dog sits and wags his tail when I bring the puppy by him as if he thinks it's a treat and like he's waiting for me to give him the go so he can have at the puppy. Doctor Dog is a very sweet boy and weighs in at 100lbs, compared to the puppies 2lbs. What can I possibly do to get Doctor Dog to except the puppy (Scrubs) into the family without risking Doctor Dog hurting him??? Please help!!

Answer
I am afraid when you are around, you will have to supervise them carefully to make them leave each other alone.  Once past 3 years old, many dogs don't want anything to do with puppies, their sharp little teeth, and their biting games.  You need to teach the puppy to leave the older dog alone.  As soon as the puppy starts to focus on the older dog, give it a sharp ''Ah, ah, ah!'' and offer it a chew toy.  Do the same with Doctor
Dog.  

When you aren't around, at least crate the puppy.  It is only natural that a puppy resists its crate at first. What the puppy wants more than anything else is to be others, you, anyone else in the household, and any other pets. In our modern society, even if we are home, other things distract us from the attention an uncrated puppy must have. The only real solution is to crate the dog when you aren't around. The dog may be happier in its den than loose in the house. It relaxes, it feels safe in its den. It rests, the body slows down reducing the need for water and relieving its self. Dogs that have been crated all along do very well. Many of them will rest in their crates even when the door is open. I think the plastic ones give the dog more of a safe, enclosed den feeling. Metal ones can be put in a corner or covered with something the dog can't pull in and chew. Select a crate just big enough for the full grown dog to stretch out in.

Leave it some toys. Perhaps a Kong filled with peanut butter. Don't leave anything in the crate the dog might chew up. It will do fine without even any bedding. You will come home to a safe dog and a house you can enjoy.