faulty gene?

Question
Hi there,  I have a female netherland dwarf and a male otter dwarf.  I breed them very occasionally but have noticed that if she has any otter colourds in her litter, they all die before the 7th week!  It's at week 5 that the difference shows in size.  I have watched them carefully and they are eating, drinking and going to the toilet as they should, but don't seem to grow like the rest of the litter.  Then they become less active and die within a week.  I have tried a course of antibiotics and adding recovery to thier diet but I still loose them.  It is only the black ones in the litters that this happens to.  Is this a genetic thing passed down?

Answer
Dear Dawn,

It does sound as if there is some congenital, linked condition with the otter coloration.  But it could be any number of things that make these babies fail to thrive.  It would take extensive testing of their blood chemistry and metabolism to determine what exactly is going wrong.

Breeding two dwarf rabbits together is risky to begin with, as dwarfing is caused by a lethal gene that makes a bunny dwarf if he has only one copy, but inviable if he receives two copies.  The latter are called "peanuts", and they generally don't make it to birth, let alone five weeks.  But there may be mitigating genetic factors that are either allowing homozygous dwarf babies make it farther into development than normal, or there could be other genetic problems at work here.  Why they would be linked to the otter color is a mystery, but such things are not unknown.

Dana