If your baby will need to take bottles of breast milk at some point, some experts recommend introducing it at around six to eight weeks. The theory is this: Your milk supply and breastfeeding relationship are usually well-established by six weeks, meaning there's less likelihood of nipple confusion or damaged nipples due to a shallow latch. (Babies suck in a different way on artificial nipples. If they treat your boobs the same way, it hurts.) Opinions differ on whether it's cool to wait as long as possible to introduce a bottle though. Some fear babies older than eight weeks will have a tougher time accepting a bottle while others say the fear is unfounded.
So shoot for six to eight weeks. This will give baby a couple of weeks to get used to her new food source before you head out. When you do it, it may be best to leave the room and have someone else try the bottle — some babies won't accept a substitute when mom is nearby. (In fact, leave the house. Even if you hide, she might be able to smell you.) And if for some (unlikely) reason baby just won't take a bottle? No biggie — she can be fed by cup, spoon, syringe, or even finger-fed with a nursing supplementer.