milk is kinda like blood?

[zanthinegirl.livejournal.com]

I sort of vaguely remember a fic where a (possibly wounded?) vampire (probably Spike) is able to get nutritional value from milk, "Because it's similar to blood".  I just can't remember where or why, and it's driving me crazy.

It's probably an older fic, and probably Spuffy.  It's possible the vampire (Spike?) was injured.  They (scoobies?) may have been feeding him with an NG tube, though that might be from another fic.

Help??

ETA: Found! It's Ichnobate, by Rabid.  And apparently it's a surprisingly popular idea!