Is bovine colostrum powder haram? I could not find any reference that it is haram.
I don't see why it would be: Colostrum is basically just a specialized form of milk produced in the earliest days of calving. Cow's milk, obviously, is halal.
It also looks like the New Zealand Islamic Food Management Division of New Zealand Islamic Meat Management considered colostrum to be Halal (at least back in 2010/2011).
The only concern I would have about it is that it is produced for a relatively short period of time after birthing, and is time-critically important to the calf's health: If the colostrum is to be harvested, it should not be done at the expense of the calf who actually needs it.
This may or may not be an actual issue as there are supplements available (obvious, really, given that that's basically what you're asking about here) which can ensure the calf is still taken care of, and they don't need all of the colostrum in the first place, but Islam does generally discourage placing unnecessary burdens on animals.
(See also the tangential (but relevant) answer I posted at https://islam.stackexchange.com/a/7071/22.)
Cows are considered halal so it's milk. Colostrum on the other hand is a pre-milk substance so it's halal as well.