why did my baby rabbit die?

Question
hello,
         my name is wendy and i have raised and sold rabbits all my life for about 9 years now.. i am 15 years old and i have 13 healthy rabbits which all are very tame and for the most part calm as can be..but my doe rabbit had just had a litter of baby's she had 4, which is very unusual she usually has like 9 babys so this time she just had only 4 baby's and a couple of days later i have noticed one of her baby's getting skinnyer and skinnyer so what i done was went to walmart and i got some just born kitten milk and tryed to feed it through a surenge to took a little of milk i done this everyday for about 4 days until one day i went out side to feed them and i reached in the cage and grabbed the baby rabbit that was sick and i had noticed it was already dieing it could'nt breath... so we juss put it to sleep so it wouldnt suffer no more.. ok what my question was is, i was just wondering why the baby died like that when the mother only had 4 babys, i thought they all would be ok because she had enough tit's for them all to feed off of so i wanted to know and why it died like that and didnt eat.. so if you could please answer my questions it would be greatly appreciated!
thank you,  Wendy

Answer
Dear Wendy,

It is impossible to know why the baby died without extensive tests.  Many baby rabbits are born with congenital defects that prevent them from thriving.  Some of these are genetic, inherited from the parents, whereas others can be caused by conditions the mother experienced while she was pregnant.  I do wonder about the latter in this case, since she had only 4 babies and usually has larger litters.

Was the mother exposed to any pesticides or other toxins during pregnancy?  Was she closely related to the father of the babies?  Both of these can cause birth defects, the former from developmental problems and the latter from bad genetics.

There is also the possibility that when you tried to bottle feed the baby it aspirated formula and developed pneumonia.  This is not uncommon when an inexperienced person tries to feed the babies, as it is a delicate operation and not easy to learn how to do safely.  Here is some information that might help if you ever have this situation again:

www.bio.miami.edu/hare/orphan.html

Please also read:

www.bio.miami.edu/hare/breeding.html

I hope this helps.

Dana