Q about line-breeding

[kat hamlin]

So, I know occasionally in other animals, people will line-breed to cement a certain trait they want.

Is this done in purebred cats?

My question is basically, how close can one breed without expecting problems with the hardiness and number of offspring?

I ask not because I breed purebred cats, but because I have foster kittens that I know came from a close inbreeding situation.  Mom mated with at least one of her sons from a previous litter, possibly both, to produce the litter I have right now.  There were 5 at first but we are down to 2.  They were born 12/26, I know for a fact, but they are way behind developmentally and in size.  One has just now started to play, the other hasn't yet.  Mostly they huddle together, eat, use the litter box (sometimes, sometimes they don't), drink, and go back to huddling.  Approx weight per kitten is less than a pound.  The 3 that died were FTT, super scrawny, dysphoric, and died seemingly of nothing.

Mom's SNAP was negative for FeLV and FIV.  The kittens are on a regular (every 2 weeks) deworming schedule for roundworms.  They have had one FVRCP vaccine and are due for another soon.  They have been treated once with Revolution and have no visible fleas.  Mom is underweight but nursed the kittens pretty well.  We took them from mom and the less-than-ideal situation they were in at about 6 weeks old.  Waiting was not an option.

My question is, is this frailty and developmental delay most likely due to inbreeding, or should I be looking for another cause?  I understand it's hard to compare a healthy purebred being carefully matched with another healthy purebred to the randomness of domestic unpedigreed cats, but I'm hoping for at least some insight into the subject.

TIA for any advice.

 

[StefanZ]

Line breeding does exist, some breeders use it now and then.  Beyond this knowledge, I dont know much.    "Matador-breeding" ie a heavy use of one or very few studs in the whole populations over several years, may give similiar results...     So this is a good reason to use many studs, for the whole population as such.

These kitten you mention, could very well be severely inbred.  Not just once.  Cats do have quite a some leeway with inbreeding before there are serious, visible damages as here.   The most common when the inbreeding begins to show, is the litters gets smaller, the average size gets lower (also for adults).

Visible problems appears even later.   Unless there is some problem build in, so to speak.  Both parents carrying some very weak gene, so to speak.

Re this huddling... Its surely for comfort, but perhaps also for warmth.  Did you tried with IR-heating lamps?  Its an useful device with many weak fosters, especielly prematures.  But also others.   An excellent complement to the usual heating pads.

 

[1CatOverTheLine]

Thankfully, in the modern world, line breeding has given way in many cases to examination of particular genetic markers in cats outside a particular breeder's line, and the shared use of those genetics.  As the use of selectable-marker biolistic particle delivery systems increases over the next fifty years, I'd expect to see traits reinforced with far fewer detrimental effects to the lines.  Sadly, this will doubtless result in the over-exaggeration as we saw with the Siamese in the 1970s.

.

 

[posiepurrs]

I don't know much about line breeding, but most of the breeders that i know use the genetic testing and the breeding quotient  as guidelines. There are computer programs to help figure the breeding quotient. - I never did because I never did line breeding.