My Chocolate Lab is due to have pups soon. I am not sure when I have to step in and bottle feed them. What should I do?

Hi I have found your site very interesting but I have one question that I am really unsure of, I hope i dont sound like i have not researched enough about breeding, I have been on the internet and read books for weeks but just cant seem to settle this question. My chocolate lab bitch is due soon and Im not too sure when to step in to bottle feed puppies, if she feeds them herself do I still have to feed them? I have sought advice from numerous people but I cant seem to get a definite answer, your my last hope!!!

Thank you,
Debbie