> While every one in the Arab world looks on in horror and SNOBISHNESS when
> you mention crosses(my dear, WHY did you ever cross an Egyptian with a
> Russian???) There is much to support this concept.
The debate between whether it is better to outcross or to inbreed
(linebreed, closebreed, or whatever you want to call it) depends upon
your long-term versus short-term goals.
Generally speaking, the closer the inbreeding coefficient, the more
"true" the horse will breed (i.e. the more the horse's offspring will
look like itself). The reason for this is that inbreeding increases the
incidence of homozygosity.
However, since most genetic faults are recessive traits (here I am
oversimplifying, but since it is possible to remove dominant genetic
faults in one generation with selective breeding, dominant genetic traits
are rapidly removed from the gene pool), if you inbreed, your chances of
unpleasant genetic faults manifesting themselves in the phenotype (what
you see rather than genetic makeup). So....if you outcross, you get that
"hybrid vigor" by masking any recessive genetic faults.
However, you have done this by creating a horse that is more
heterozygous, and therefore, its offspring are less likely to be just
like mom or dad (even if you breed a half-arab to a half-arab).
As an individual making this decision, it is best to decide what your
purposes are. Do you want to create an exceptional individual or are you
breeding for breeding stock.
If you are breeding for breeding stock, and you decide to inbreed
(linebreed, close breed, whatever) because you want to increase your
incidence of homozygosity, then remember that as a breeding philosophy
this only works if you are willing to ruthlessly cull your herd (i.e.
you are going to have some horses that you have to throw away).
Outcrossing is much safer.
Breeding and arabian to an arabian is inbreeding compared with breeding
an arabian to an appaloosa. Your chances of getting a horse with genetic
faults is therefore lower.
> All you knowledgeable people out there, pour out the ideas on this subject.
> What crosses the best as for breed /breed or should we really be looking at
> individual /individual regardless of breed???
There are some breed/breed crosses that have a tendency to throw a
specific type. But you should always be looking at the individual as
well. If a horse demonstrates a genetic fault, that fault will probably
be passed on (genetically atleast) to the foal (since most faults are
recessive and would not be displayed if the horse were not homozygous for
that trait) although it may not become apparent. THerefore, no matter
what breed your horse, and what the horses in its pedigree looked like,
it is best not to breed horses with obvious genetic faults.
If you are only breeding one or two horses, it is best to stick with
outcrosses. If you are planning a breeding program that you intend to
span generations, you can experiement with closer breeding practices with
the hope of eventually removing horses with recessive genetic faults from
the herd entirely.
Have I muddied the waters further?
kat
Orange County, Calif.