Use Diversity and Pedigrees to Negotiate Common Breeding Pitfalls

Know your pedigrees over your breeders

Have you ever wondered how to go about selecting the right cats for your breeding program?  Well, picking wanted traits will always remain a personal choice but perhaps we can provide some insight here on what you should steer clear from. The following outline expands on our experiences and the benefits of Burmese outcrossing and introduces using a pedigree as a means for determining ordinary from pragmatic.

When selecting any breeding pair you can choose from what’s right there in your back yard, what you might research and obtain from another breeder, and from wider ranging possibilities of selecting from overseas sources. Each approach has a path and each path will contain complexity. This selection process pretty much works no matter which path you choose.

Thanks to our myopic registries, our Burmese friends invariably form an exclusive pool. No matter how large our longstanding this pool has become – our national pool is by no means diverse. The resultant genetic loading can only represent the difference between our fittest genotype and the average fitness of our entire population. This diversity level has narrowed over time with the overall average diversity really only heading one way – down. This means our average fitness standing (overall health vigour and ability) can only remain stable or deteriorate. A decade ago one might have claimed our Burmese were holding their own. The evidence more recently; smaller litter sizes, increased neonatal death, increased rates of flat chests, higher frequency of genetic diseases or impaired immunity, suggests otherwise. This evidence is very much pointing to a deteriorating pool of genes.

Natural selection is the survival mechanism for any species and a primal reason for why our cats would get this right, if left to their own devices. Any individual cat will carry a loading of four or five genes which manifest as defects and are therefore susceptible to fatal disease or mutations. Generally, this level of genetic loading will not significantly affect an individual cat because the defects exist as a single allele, or form of gene. But if you heedlessly mate such a cat with its relatives, the odds for matches within those four or five alleles increases – as does the risk for disease or mutation. By analysing pedigrees you can defend against some of the obvious problems and so create your very own form of natural selection.

To further illustrate the demise arising from inbreeding, look no further than the kings of the Spanish Habsburg dynasty from the 1500s. The family line eventually disappeared but while it existed the dynasty was given to frequently venture into consanguineous unions. Their extended pedigree of 16 generations, involving around 3000 persons, shows an inbreeding coefficient moved strongly over the generations from 0.025 for King Phillip I, the founder, to 0.254 for Charles II. It has been determined that two distinct and separate disorders existed most likely the result of recessive alleles at unlinked loci. Although this illustration represents a historical conclusion, on what can only be described as a complex clinical profile, the death of Charles II at the age of 38 led to the extinction of the dynasty.

Coming back to our Burmese friends, it goes without saying that cats with desirable traits will continually be used to propagate such traits. Over time, genes upholding those traits will skew the gene pool and become more common. As will the equivalent four or five defective genes. The result can manifest as accelerated loss in alleles and increased problems showing up in progeny. Males are more susceptible because it only takes one gene on a chromosome A useful defence to such an outcome is to conduct meticulous analysis of pedigrees and adopt an unswerving discipline. So exactly how do you use a pedigree to stand up this defence?

There is no real way of knowing a defect exists with any cat unless a breeder opens up on a linked trait. The things to look out for are both predictable and logical. First up, note the name of catteries behind each Sire and Dam so as to determine if they have a reputation for producing high quality Burmese. DM is a title used that is associated with good breeding outcomes. Look for how many cats in the bloodline have this classification. Any preponderance of sires or dams within the generations needs careful consideration. If the cat is of low quality, obviously frequent appearances should be a cue to eliminate from further consideration. If the cat is of high quality, then proceed with caution based on what you intend to mate. Relatedness comes with desirable traits but it could also bring into existence mutation. Where possible, diversity will always de-risk your selection.

If a foundation population of Burmese cats produces a high rate of deleterious recessive genes you will find a response manifests as conditions propagating into progeny. The real, hard facts show the problem you will encounter is breeders cover up any conditions. Because so much effort, time and cost are invested into bloodlines, they would choose to see that investment continue and not be wasted. This means breeders will be entirely reluctant to openly discuss any problems which may present. For this reason any due diligence needs to come from you.

Some key points then. If most of the males show a condition, it will represent a dominant disorder, meaning that one of the parents has that disorder. If a 50/50 ratio of Sires or Dams shows a condition then an autosomal disorder exists. This means the condition manifests further back in the bloodline as a recessive disorder, and neither parent might show the condition.  The more frequent the same cat appears within a pedigree the higher the risk for recessive genes to jeopardise your breeding program. Inbreeding is inbreeding. Whether is appears at generation 4 or commenced at generation 12, the fact remains you will take on the same risk. Look for catteries that encourage outcrossing and diversity because no matter how frequent, this simple contribution acts to mitigate risk of manifestation into conditions mentioned above. Pedigrees show up to 4 generations of bloodlines. The onus is on the consumer to research into earlier generations to confirm an acceptable risk exists based upon the above observations. After reading this passage it will become abundantly clear why Burmese breeding in Australia is not straight forward. Once you review even a few pedigrees you will soon find that conditions exist to confound sound selections. When looking for potential breeding options within Australia the opportunity to look internationally might just appear rosier.

Not all Breeding is equal

    Merlin says, “not all breeding is equal”

Aussie’s need to apply a disciplined approach to Burmese breeding. The right approach is critical in order to reduce the risk of mutations; from stagnant bloodlines, community-wide reluctance to inject new bloodlines, longstanding in-breeding, and the inadvertent passing on of unknown bloodline defects.

Not all matings are equal. There are three recognised types of breeding: outcrossing, inbreeding, and line breeding.

Outcrossing means breeding to unrelated stock in order to strengthen one’s lines; the term hybrid vigour is a key benefit of outcrossing. The downside with outcrossing is that along with all that vigour can come some undesirable or unpredictable genes, because with increased vigour comes a modicum of increased variable genes. The upside to outcrossing is that it increases genetic diversity, thus reducing the probability of an individual being subject to disease and reducing genetic abnormalities.

Inbreeding means selecting crosses to parents, and crosses to litter mates. It is important to know what one has in breeding stock to get the crosses right. In-breeding is the easiest and quickest way of learning what is bad, but even more significantly, what is good might just become apparent as well.

Line breeding means breeding to a family of cousins of similar lines that have produced your own stock. Upgrading stock to retain the best characteristics in each related line, and then selecting to only line breed with an outstanding individual. The key goal is to get the genes you really want. To do this requires knowledge, patience and longer term goal setting.

Pure breeding means cats that have registered ancestry, generation after generation standing behind them, and that means they should produce predictable and like kittens.

Here at Starkatz, we recognise and embrace the potential benefits of outcrossing and combine that benefit with our well practiced pure breeding discipline to produce lovable Burmese cats of renowned temperament and well-being.

Breed diversity and cat domestication

How does your breeding program stack up

 

Rumby recons, “getting this inbreeding stuff wrong makes for a risky breeding program”

Depression caused by inbreeding tends to negatively affect traits within a breed which might be positively affected by outcrossing. The type of traits affected will certainly include; fertility, longevity, growth and well being.

Any cat, but especially those within the Burmese breed (because so few new blood lines have been imported over may years), will have an inbreeding level for a specific animal or mating outcome which can be measured by calculating an inbreeding coefficient. An inbreeding coefficient represents a probability percentage (%) for any allele (i.e. pair of genes at a specific location on the chromosome) to be identical, by descent.

Typical inbreeding coefficient percentages are as follows. This is assuming no previous inbreeding between any parents.

Relationship Inbreeding Coefficient
Mating to parent (Sire to Daughter) 25%
Full Siblings (sire to dam with a common sire and dam) 25%
Half Siblings (sire to Dam with a common sire or dam) 12.5%
Half Cousins (sire to dam with a single common grandparent 3.1%

The “accuracy” of the inbreeding coefficient value that is calculated will depend on the accuracy and depth of pedigree that is recorded. For example, the accuracy of inbreeding coefficient that is calculated would be higher in an animal with 10 generations of pedigree on both the sire and dam side, compared to an animal with 10 generations on the sire side but from a dam with little or no pedigree recorded.

Some breeders will argue that “considered” inbreeding programs can produce a single “superior” outcome by concentrating on desirable genes for certain type or traits (i.e linebreeding). Of course, aiming to produce a superior outcome might just result in inferior animals through inbreeding depression or the appearance of recessive genetic conditions. So let’s explain this using a different example (horse racing) so that the odds make a significant impact. 

Black Caviar has common ancestry in her pedigree such as the stallion called Vain. Vain is Black Caviar’s paternal great grandsire as well as maternal great-great-grandsire. Vain also has a second sire, Silly Season, further back in the pedigree that appears on both sides of the pedigree. Now if you’re banking on a next generation winner then you would wish for a superior outcome. Should a recessive gene pop up you might find the impact manifests as an extremely reduced bank balance. When economics weights on the outcome you really need maximum certainty.

There is no gold standard for an acceptable level of inbreeding within any breeding program. One would hope that experienced breeders would manage inbreeding rather than simply let it play out. That said, breeding programs that simply avoid inbreeding without injecting desirable genetic material from select animals, to be used within their mating programs, are unlikely to be sustainable over the longer term.

Average inbreeding coefficient levels that calculate to around 5% within any breeding program are considered low. Inbreeding levels between 5% and 10% are generally considered to be moderate levels of inbreeding that warrant more careful management. Whatever you determine as your level, containing an increase to inbreeding level over time is as important, if not more important, than managing an overall level of inbreeding within your breeding program.

Over time, higher levels of inbreeding will ultimately invite loss of genetic diversity within your breeding program. This could mean the loss of valued alleles that you may have counted upon for maintaining desirable traits.  This will also put at risk a the amount of genetic variation from which to make future decisions around mating selections. Putting your head in the sand is unlikely to bring about returns you might wish for your breeding program. A very good thing is we don’t need to deal with a future racing budget.

Breaking down inbreeding

 

Burmese [Euro Burmese] in Australia

The problem: put to the 2015 Judges Conference…

All Burmese originated from the same cat, but their breeding separately in different parts of the world has led to different styles of Burmese. Each of these styles has almost universally been kept apart from the others, so that there is an American Burmese and a number of variations on the English or European Burmese; this latter being the Australian Burmese.

There is a widely-held view that Burmese in Australia have a number of problems —
– Their gene pool is very small, resulting in a high in-breeding rate
[co-efficient]
–  Litter size has decreased markedly
–  Natural birth rates have decreased
–  Animal size has decreased markedly
–  Not all breeders are willing to share access of their stock to other
breeders, which accentuates the above problems.
–  A number of existing Burmese lines in Australia have the disease
Hypokalaemia (HK), the presence of which can be identified by a DNA test.

–  Dr Leslie Lyons, prominent cat geneticist from the University of
Missouri, has led a study which found that Burmese [regardless of their
style] have the lowest level of genetic diversity of all 20 breeds of cat
studied [and therefore presumably one of the lowest levels of
genetic diversity of pedigreed breeds of cat.

–  This study concluded that as a result of the above concerns,
pedigreed Burmese will cease to exist within 20 years if a solution
is not put into place.

–  Not all breeders agree either that there is a problem or with the
results of Dr Lyons’ study, but the concern is widespread enough
for a solution to be proposed. There is nothing to lose in not
doing so and potentially a lot to gain.

A Proposal: 
–  That Australian Burmese breeders be allowed to outcross to any
or all of Thai cats, American Burmese and Mandalays, with the
following controls —
–  Any such outcrossing be done only with the prior approval of the
relevant registration body and through the use of an approved
experimental breeding programme. All the normal generational
checks, inspections of stock and marking as Gen 1 for 1st cross to
G4 for full register be conducted.
–  Thai cats are himalayan-patterned [Cs], so offspring from
outcrossing to them will need to be selected with a view to
eliminating the Cs gene. The available DNA test carried out
through correct protocol i.e. by a veterinarian or accepted officer,
would achieve this, so that freedom from the Cs gene could be
recorded on the pedigree of the cat concerned and ensuing
pedigrees on which the cat appears.
–  All American Burmese used for outcrossing are to have all
available DNA tests for known conditions [Head Defect, Gangliosidosis (GM2) and
HK], using the same protocol so these conditions are kept out of
Burmese breeding programmes in Australia.
–  Only Mandalays free from the cinnamon gene, from Oriental and
Abyssinian be used for outcrossing and that DNA testing be used to
verify this.

–  The use of the above 3 outcross breeds be recorded on pedigrees
by “Thai”, “AM Burmese” and Mandalay, respectively.

–  A note should be displayed on the pedigree of all Burmese in
Australia advising either that “This cat has only Australian
Burmese on it” or “This cat has “Thai”, “AM Burmese” or
“Mandalay” on it.

–  The above outcrossing be initially allowed for a period of 10
years, to be reviewed toward the end of that time for possible
extension/s of time.

–  The above outcrossing be approved by all CCCA member bodies,
with a view to attempting to have it approved in all Australian
registries.

–  No breeder will be required to use any of these outcross breeds if
they choose not to, but it will enable those who wish to broaden
their gene pool and attempt to reverse some of the problems
outlined at the start.

–  All Burmese breeders in Australia be required to have the DNA
test for GM2 performed under correct protocol, as
above, on all existing Australian-line breeding stock unless both
parents have been DNA tested and shown to be GM2 free.

Pedigrees should clearly state either GM2-free or GM2-carrier.
This proposal is a modification of the proposal presented to the
2015 Judges Conference and is submitted on behalf of the CCCA
November 2015 meeting by: –

– Dr J Nicholls [Burmese breeder, noted veterinarian and member
of CCCA Breed Council] and
– C Merritt [Chair of the CCCA Judges Conference and member of
CCCA Breed Council]
– M Ristuccia [principal Mandalay breeder],
– Beverley Jones [source of original Burmese proposal to the conference
and Burmese breeder].
– R. U’Ren [co-ordinating the proposal].

Taking a Chance – Outcrossing Burmese Cats.

Should anyone contemplate the undertaking of a Burmese Outcrossing program then read on to find out how such an endeavour might actually just play out. Any prospective American program will include finding a suitable American Burmese, developing a relationship with the owner, navigating a bureaucratic process that will test the most hardened importer, and setting up an Australian home. None of this happens overnight and it’s not a program for the uncommitted or for those with limited time or capital. The result however will be pleasantly satisfying and it is more than likely that you’ll end up with a productive and dependable breeding future.

First up, be very aware that there is no incentive and zero advantage for any breeder within the United States to sell to a breeder in Australia. The export requirements are some of the toughest of any country and the process will be case by case, long and drawn out. The administrative requirements are bewildering at best and require disciplined timing and sequencing to obtain the right contributions from the many stakeholders. If you can work past all of that you’ll need to find a kindred soul who just has a love for our affectionate and noble Burmese cats. Finding that one who is then willing to go those extra yards to overcome each and every import challenge will simply be a lottery. But if you can see past all of that the results to be achieved are totally worth it. You can bring diversity into your breeding program and you’ll just love the result.

Every project must have a plan. The Department of Agriculture’s animal import Website is the natural starting place, but you’ll certainly need a healthy dose of resourcefulness to bring your program home even after using that. From forms that do not function using some internet browsers, to undocumented or variable fees for Government approved vets and Official Government vets, veterinary health checks, the obligatory blood testing regimes (both general and rabies), the application for an export permit, quarantine accommodation, comfort stops, and IATA approved transport crates – the process quickly turns into a virtual minefield. Add to the mix the different time zones and one can easily imagine the perseverance required, the draw on one’s time, the lightness in one’s pockets, and the fingertip grip on one’s sanity. The export process is not for those that are faint of heart.

If you have a breeding program that finds mothers and kittens having trouble at birth or litters not meeting the normal development milestones, then a Burmese Outcross Program might just be for you. The experience explained here finds mothers having trouble free births, kittens strong and robust, total litters surviving to wean and no dull or poor doer’s anywhere in the lot. Noticeably, all kittens are alert and have met every development milestone to date. Try yourself and see if you can pick any differences between any normal Australian litter and two outcrossed litters as shown in photos provided below. The benefits from Outcrossing are there to be taken and can only be given two big thumbs up.