We think we know now what the problem is with Cupcake’s litter but sadly there is nothing we can do for her remaining kitten Juno other than hope and pray.
If we’re right (and I really think we are) it’s a condition known as 'neonatal isoerythrolysis' or 'haemolysis of the newborn’ which is due to an incompatibility between the mother’s blood group and that of her kittens. The kittens are born healthy, but during their first day of life they absorb antibodies from the mother's colostrum (first milk) which destroy their red blood cells causing anaemia and jaundice. Sadly there is nothing that can be done to reverse the process once the kitten has absorbed the antibodies so bottle feeding is of no help unless its started as soon as the kittens are born, at which time you have no idea that anything is wrong because they’re healthy.
Juno does have a ray of hope – well two really. She may have the same blood group as her mum or she may be one of those lucky kittens who are only mildly affected or, better still, remain unaffected.
She is the smallest of the litter so maybe in the general scramble for that first feed she didn’t get as much as the others. It’s only in the first 16-24 hours that the kitten’s gut is permeable enough to allow the antibodies to pass though it and into the bloodstream.
If anybody is interested, in particular anyone in rescue who has been baffled and distressed by the sudden death of apparently healthy kittens, this is a very informative article.
http://www.fabcats.org/owners/blood_groups/info.html Warning. You may find this final paragraph distressing. We’ve arrived at this conclusion as a result of something we witnessed in connection with the death of the kitten number 2 and things we were able to rule out after the vet performed a PM on him, plus the fact that on examination of the insides of the mouths of the remaining live kittens yesterday two showed signs of jaundice. Juno's did not. She is all black (like her unfortunate siblings) so we wont know whether she is developing jaundice without examining the inside of her mouth which is not something we’re prepared to do given that it will not help one jot.