You will produce colostrum whether or not baby feeds at the breast - so I'd say give the colostrum for a few days. When you stop feeding, your breasts automatically stop making milk, so in a couple of weeks you shouldn't have a problem (although I do know some women who claim to still had some milk 10-15 years on, which "squirts" whenever they hear a baby... I chose to take that as a "horror story" because I was a leaking, spraying queen and don't have that problem, even with my own child).

You'll notice when the milk comes in: baby will feed for a bit longer and not be hungry straight after a feed.

I was told DS was starving on day 3 (my milk came in day 4) so gave formula (it was that or the midwife was going to do it herself... why did I believe that threat?). What I did was use a little egg-cup and DS lapped it up from that, a bit like a little kitten. After a week we introduced a bottle after feeds, with a really slow-flowing teat. I was told DS "should" take 300ml every feed when I was starving him, but anything over 200 was OK. So maybe that's what to aim for? When I was mixed feeding, the neonatal nurses didn't really mind how much DS took so long as he'd had a feed and had most of the expressed stuff.

HTH!