author Kristen Wiley Imperial RagaMuffins
A year ago I sent an email to all our breeders to discuss our breed and the outcross. As the Breed Chair for ACFA I was asked to discuss the outcross and to make changes to what is currently
allowable. I compiled all the responses and started really researching our breed database. We have seen the repetitive use of some of the same pedigrees and the seemingly shrinking pool of
our genetic diversity within our pedigree program. With that in mind I began working with a company (Optimal Selection) that does genetic evaluation of cats and determines a specific
samples heterozygosity.
For those maybe not familiar with the term heterozygosity I will explain that quickly. It is the term used to relate the genetic diversity. Hetero meaning opposite alleles of the same gene. The
greater the heterozygosity, the greater the genetic diversity. So a cat that is very homozygous (meaning same alleles of a gene) will typically be very “typey” and or line bred. I line breed my
cats to keep as closely to the type I desire in our breed. In doing so one risks loosing genetic diversity. As our gene pool is quite small we worry about the need for an outcross to help widen those numbers.
Currently when a breeder is considering a breeding they may call and ask to run a coefficient from the groups database. We like to keep our coefficient or inbreeding less than 10%. The number we get based from a coefficient is determined by the cats in the pedigree and not what actual genes the cats received from its parents are. Although heterozygosity might not vary too greatly between siblings, it is very interesting to see the differences. What I think is more interesting is correlations between heterozygosity numbers from cats of our breed vs other breeds and vs random bred cats ie barn cats DSH/DLH. This is the number to look at when worrying
about questions like “Does our breed need a outcross?”.
With the new information from Optimal Selection we can better predict a possible pairings heterozygosity. Since working with Optimal Selection my worries about the gene pool have
lessened. I do not have a huge in depth look at our gene pool through this company since there are just barely over 30 samples given. I do line breed and I was very surprised with the heterozygosity within my own cattery. So that is the info I presented to the committee after receiving requests for us to add to our outcross.
Optimal Selection has generated numbers from their samples for averages of breed heterozygosity and uses a scale to compare with pedigree cats in general as well as random bred
cats. Random bred cats heterozygosity is 38.7% compared to pedigree cats average at 33.7%. We finally have the minimum 30 samples needed to generate a median for our breed and it is
36.2%. Below are other breeds current average percentage for heterozygosity. If a breed is not listed it means they do not have enough samples. Numbers can change as more samples are
given to them.
Abyssinian 28.9%
Balinese 24.6%
Bengal 33.2%
British 35.7%
Burmese 21.3%
Cornish 32.9%
Exotic 33.1%
Korat 20%
Maine coon 34.7%
Norwegian 37.8%
Ocicat 30.2%
Oriental LH 26%
Oriental SH 24.5%
Persian 33.4%
Ragdoll 33.9%
Russian blue 31.7%
Siamese 24.1%
Siberian 38%
Somali 30.6%
Sphinx 34.7%
Turkish angora 36.4%
Turkish van 32.8%
I would LOVE to see more breeders using the Optimal Selection as a tool. It is an expense ($100/cat), but one I deem worth the results. The comprehensive report also gives blood type aswell as tests for numerous diseases including PKD1 and HCM. I think looking at the numbers comparing heterozygosity to a cats inbreeding especially interesting and think it’s indicative to our pedigrees errors. Either error of entering cats in or error of parentage. Cats with very similar
heterozygosity but vastly different COI and vice versa is odd. It confirms my thoughts on errors and also the lacking in solely using a coefficient for such decisions.
The use of the DLH as an outcross was brought up. I do have concerns about that. For one, I know of instances in our breeds history where cats have been registered as DLH for our breeds
use that possibly are purebred cats. My concern is the actual diversity within those cats we would use of DLH. Using Optimal Selection would tell us that but we cant implement its
requirement to use a DLH. I know from my experience growing up on the farm that our barn cats were inbred. Cats in the wild don’t use discretion when it comes to mating. And even though tom cats will wander there is still a circle of same genes running in those cats wandering.
My suspicions are slightly confirmed by the Optimal Selections number assigned to a random bred cat since it is not higher.
The average heterozygosity for a random bred (barn cat) cat is 38.7% and for a pedigree cat average is 33.7%. So the higher the number the more genetic diversity. Now also realize that
the number between a barn cat and a pedigree cat is not huge, but it will help you reference where our breed is on that scale.
Pedigree average 33.7%
Random average 38.7%
RagaMuffin average 36.2%
Below are RagaMuffins in the data base (the second number is that cats coefficient based off a 10 generation pedigree) They are not relatable as far as heterozygosity to coefficient but more to the
fact that we say breed under 10% coefficient to have safe health and diversity. So this will tell you ok we say 6% coefficient is great and relate to ok here is this cats heterozygosity or actual genetic diversity. In the following , bold print numbers next to each other are FULL siblings for comparison of heterozygosity vs coefficient.
heterozygosity vs coefficient . The third number percentage in each line is for samples I didn’t have pedigrees for to know coefficient
36.1% 11.1% 34.1%
36.5% 6.7% 36.7%
36.8% 6.7% 36.6%
33.9% 11% 34.4%
34.4% 11.3% 36.5%
34% 11.3% 39.9%
34.5% 7% 38.6%
34.2% 12.7% 38.9%
32.8% 12.4% 35.4%
34.4% 12.4% 36.3%
33.7% 16.1%
35.2% 6.4%
Samples from first generation BLH outcrosses using two sets of different parents:
39.8% (I dont have the BLH parent number but the Ragamuffin parent had a 34.2%)
39.3% (The BLH parent used had a 37.3% and the ragamuffin had a 35.2%)
40.3% full sibling to above kitten
Numbers from siblings of our Selkirk outcrossings and are 2nd generation.
38.4%
37.1%
So, some of the outcrosses have greater genetic diversity then that of a random bred barn cat!
That is why I think using a DLH is not the best answer. Cats in the wild can’t always be as diverse due to the small wandering circle of genes they can get to. And also they do breed to their siblings, parents etc….. With how we can ship cats today, it is more genetically diverse to get cats of known pedigree breedings than to use a DLH.
As far as “Do we need an outcross?” Well the numbers from the two BLH are nice to see. But if you look at the cats in the database
that are purebred RagaMuffins all but one are over the average of the average pedigree cat. This is why I say I don’t necessarily worry about adding one. Yes it will help and add diversity, but I
believe we will be ok without. Granted this is a small pool of our breeding pool cats. I would better be able to evaluate if there were more cats in the system.
Here are some predicted heterozygosity numbers vs trial mating coefficients with some of the samples.
predicted heterozygosity vs coefficient
37% 6.5%
36.5% 7.4%
33% 18.9%
36.3% 6.4%
35.4% 10.3%
35.3% 9.7%
37.5% 5.6%
36.1% 5.4%
35.3% 7.2%
I want us to make informed decisions. And this has been a very useful tool! For now ACFA is not adding to their outcross. But it is nice to see all this information for future reference in
determining the future for our breed.