Coefficient of Inbreeding.

[Judy]

WHAT IS COI

COI stand for Coefficient of Inbreeding. Essentially, it looks at how
related dogs in order to to measure how genetically similar they are.

WHY SHOULD I CARE?

There are consequences to being genetically similar, some good, some bad.
The fact that flatcoats (indeed every dog breed) are so genetically similar
is what makes them flatcoats and why if you breed any flatcoat to any
flatcoat it will look recognisably like a flatcoat. Same goes for every
breed and, of course, for every individual species, from the giant panda
to the fruit fly.

OK, GO ON... BUT PLEASE KEEP IT SIMPLE...

Many of the 20,000-odd genes that go into every flatcoat are Œfixed¹. That
means that every flatcoat will have two identical copies of them one
inherited from their dam; one for their sire.

Others however, are not so fixed such as those genes in flatcoats that
code for colour. Hence why flatcoats come in black, liver and occasionally
yellow.

Genes always come in pairs. The gene-pair is called an ³allele² (pronounced
al-eel with the emphasis on the eel).

When the pair is identical, it is called ³homozygous² (home = same)

When the pair in not identical, is is called ³heterozygous² (hetero =
different)

³Allele², ³homozygous² and ³heterozygous² are three good words to understand
if you are a dog breeder and scientists will be very impressed if you use
them. (And even more impressed if you use them correctly...)

Homozygous and heterozyous are terms often used more generally, too, when
talking about diversity.

The more gene-pairs that are homozygous = less diversity
The more gene pairs that are heterozygous = more diversity.

Geneticists in the main consider diversity a good thing.

SO NOT ALL THE PAIRS OF GENES ARE IDENTICAL?
Correct! And this is what gives us variation. It¹s why, as mentioned
above, flatcoats come in three colourways. And it¹s what makes some bigger
or shorter or faster or cleverer or more able to withstand disease than
others. Of course environment can play a big role, too, but the raw
potential for every dog lies in its genes.

I THOUGHT WE WERE TALKING ABOUT COI..?
Homozygosity/heterozygosity is what COI measures. A COI programme computes
the likelihood of a dog having inherited the same genes from a common
ancestor.

GIVE US A DEAD SIMPLE EXAMPLE
1. Breed two completely unrelated flatcoats
2. Mate two of their offspring together
3. What is the resulting puppies¹ COI?

In this instance, the puppies¹ COI will be 25 per cent ie, on paper, they
are likely to be 25 per cent genetically identical as a direct result of
having common ancestors in this instance, the same grandparents.

YOU SAY ³STATISTICALLY²...?
Yes, in reality, they could be much more that 25 per cent genetically
identical/homozygous or much less. The only way to know for sure would be
to minutely examine every dog¹s DNA which would be impossible (at the moment
at least). But the statistical likelihood is nevertheless very useful to
dog breeders.

WHAT ABOUT OTHER EXAMPLES?
The following matings produce the following COIs:

Parent/offspring: 25%
Full siblings: 25%
Grandparent/grandchild: 12.5%
Half-sbling: 12.5 %
Great grandparnets/great grandchild : 6.25 per cent
First cousin: 6.25 per cent

WHAT ABOUT OTHER COMMON ANCESTORS?
COIs are much more than looking at who a dog¹s parents.. COIs also track how
related dogs are much further back in the pedigree.

Look back 10 generations in any own family trees and you are very unlikely
to see the same name twice (well, unless you¹re a member of the Royal
Family... ) This is not true for our dogs, though. The same names can
appear many, many times. Traditionally, breeders have very commonly used
grandfather/grand-daughter matings (and often even closer) to cement certain
traits.

To get a true picture of inbreeding, then, you should go back at least five
generations and ideally 10. As you go further back, in most instances, the
COI is likely to rise.

WHY ARE HIGH COIs CONSIDERED A PROBLEM?
Two reasons:

1. inbreeding will help cement ³good² traits but there¹s a danger of it also
cementing bad ones. In particularly, it can cause the rapid built-up of
disease genes in a population..
2. even if a breed of dog is lucky enough to be relatively free of serious
genetic disorders, inbreeding is likely to affect our dogs in more subtle,
but no less serious ways.

These include smaller litter sizes, less vigorous/viable puppies, fertility
problems and weakened immune systems. These effects have been VERY
well-documented in other species. So much so that farmers, who used to
breed livestock in much the same way as we breed dogs, have changed the way
they breed their animals. In Holstein-Freisans, for instance, they try to
keep COIs around the 6.25% mark. In fact, farmers so recognise the benefit
of hybrid vigour that much of the meat we eat, milk we drink, and eggs we
boil is from crossbreeds. That¹s because the yield is likely to be
more/healthier/disease resistant than that from purebred stock.

A study of standard poodles discovered that dogs with a COI of less than
6.25% lived on average almost four years longer than standard poodles with
COIs over 25%.

Now nothing in genetics is inevitable. There ARE some examples out there of
very inbred populations that appear to be pretty healthy and whose
fertility/fecundity have not been affected.. But the above effects have been
observed way too often to totally ignore the risk.

RIGHT! I WANT TO KNOW WHAT MY DOG¹S COI IS! TELL ME HOW!
Working out COIs in dogs would be devilishly difficult to do manually.
Fortunately, there are various pedigree programmes which do the whole thing
for you well, except that you have to enter the names.

You can download a two-week free trial of Compuped (Windows only) from here:

http://www.compuped.com/compuped/

There¹s a Mac programme avail here with a downloadable demo:

http://www.iosphere.net/~lrmccue/mcq/scamp.htm

(Haven¹t tried it tho)

Breedmate, meanwhile, offers various options:

http://www.breedmate.com/

ANY EXAMPLES I CAN HAVE A LOOK AT?

Yes.

Here¹s how the Swedish KC database lists COIs links to individual
flatcoats from this page:

http://www.rasdata.nu/flat/htmlhund/htmlhund.htm

And there are now numerous individual breed databases that do now list COIs.

Here¹s a good site for Chessies...

http://www.chessieinfo.net/p1.htm

...that links to this pedigree database that lists 10-generation COIs (the
percentage figure after the dog¹s name)

http://www.chessieinfo.net/pp_search.htm

BREED AVERAGES
It varies enormously. The recent Imperial study revealed breed averages for
the 10 breeds they looked at of around 4 per cent. Within each breed,
though, there was enormous differences, with many dogs in the KC database
with COIs over 25% (the equivalent of a mother/son mating).

IMPORTANT CAVEAT
COIs are not the be-all and end-all of a dog. They¹re just one measure. So
don¹t freak out if you run the figures and discover you have a flattie with
a 10-generation COI of 30%. Likewise, if your flatcoat has a COI of only
1%, it does not guarantee its health and fitness.

[trekmoor]

Wowwwwwwww ! It's an awful good job I'm not having a flatcoat if I have to learn all that stuff !

Wullie