A-Kerr's Bengal cats since 1989

Creating a breed, the choices we make

Human intervention begins when a decision is made to put two cats together and create babies.  One could say, putting two cats together allows nature to do what comes naturally, however nature bases selection on survival of a species, not on how it "looks".  The moment selection is based on appearance; the genetic selection has been changed.

When genes are combined to enhance appearance through human perception,  "engineered" versus  "nature selection," the responsibility of outcome shifts, The creator has changed from nature, to human.   This requires awareness of consequences and responsibility for the decision made.  Before proceeding ask:  Why are these two cats being put together?  What is my intent?   Am I willing to be responsible for the consequences of this combination?

What are the criteria for selection?

Selection of breeding pedigreed cats are (should be) based on three attributes:    

To be recognized by a cat association, one of the criteria is to have distinct breed characteristics passed from parent to progeny.  Consistent replication requires cats homozygous¹ for those characteristics.    Simply put, homozygous is “like breeds like” and the breed breeds true. 

The Bengal cat has a broad gene base, combining non-domestic and domestic genes.  The broadness of the base has positive and negative aspects.  Many domestic breeds have a narrow genetic base due to unnatural selection of breeding mates, the human factor narrowing the appearance genes, this also limits the gene base for health.  Sometimes, to lock in a particular look, humans select cats that produce health problems, structure abnormalities, internal problems, and immune system suppression.   The good news is Bengal cats have a broad base giving selection for health and temperament.   The bad news is there is a broad gene base, giving a wide range in the overall appearance. This diversity in outcome of breeding means it does not breed true.  

How to breed true and not sacrifice health and temperament?

This is an important question facing the cat fancy today.  The reason people select pedigreed cats as pets, is to have a record of health and temperament coming from the parents as well as the appearance of the individual breed.  As breeders, this needs to be our most important focus... to breed temperament and health for life long companionship and care; as well as, creating beauty.    To do this several things must take place.

Cat shows are designed to evaluate breeding stock and vigor.  They should not be "just another pretty face" but an evaluation of the cats with the most desirable traits to pass on to their progeny.   While this is the ideal scenario, it often falls short because some genetic information is not in the phenotype of the cat.   This information only becomes apparent when bred and often not in the offspring but in the grandchildren.  DNA testing may soon be the means to get a more complete selection model in breeding.   Cat shows allow a view of the overall breed as well as a forum to openly exchange information not only on a particular breed but all breeds.

Open exchange of information is being made more possible through publications and the internet.  As information is collected and exchanged, we become better able to share knowledge and seek solutions.   This is vital to the cat fancy. 

While one would hope that disclosure is a given... it is not.   It begins with disclosing what might be carried in a line as far as color is concerned, then structure, and then the potential problems noted in the progeny.  Remember as well, it is often not the first generation but the grandchildren of a line that exhibit the traits.   It is important to keep records of progeny so patterns are seen.  Disclosure will allow the breed as a whole to move ahead.   There is no forum for this at the present time.  

Back to the original question of: How to breed true and not sacrifice health and temperament?  It is possible.  A classic example of a very homozygous species is given to us in the cheetah.  Cheetahs are extremely homozygous, studies of transplants have shown that there is little problem with rejection in the cheetah.  So how does a breed progress by becoming more homozygous and not loose its genetic vigor? 

 It is helpful to go back to essential genetic knowledge and work from the point of what is known or at least not proven false.  What is known about inheritance of a certain attribute?   Perhaps a better way to ask: What hypothesis ² is followed?    Most of cat genetics are hypothetical, though record keeping and compiling information clarifies, it also brings to light deeper questions.  The non-domestic genes bring new elements to the domestic genes and have skewed the knowledge base... greatly!

So what are desirable Bengal cat attributes? 

            Rosetting

            Horizontal flow

            High contrast of pattern to background

            Rounded ears (interpretation of small to medium)

            Definite delineation of whisker pads

            Whited belly

            Chinstraps and facial markings

There are other areas to delineate, but this will give a point of discussion.

The Bengal cat has evolved since first registered in 1983 by Jean Mill.  The people of vision, who allowed the breed to move from the realm of "exotic curiosity" to that of the show halls with other domestic, brought us to today.  Controversy bonds, strong opinions are stated at times in heated discussions and the compromises demanded of resolving issues and moving forward divide.  One of the main areas is that of genetic diversity. The debate centers on:

We are extremely heterozygous³ .  

The new standards point to making the Bengal cat more homozygous.  To be more consistent in type as well as coat the Bengal cat breeders will vote to define the look they are breeding toward as "perfection."  This is quite a challenge, and requires compromise.   It is also an essential process to help breeders in the selection of breeding cats.  

When defining the standard, a 100 point system that is divided on point values on head, body, and coat.    Depending on the phrasing and the accounting of the points, a cat is defined.   Because the size difference in cats is minimum as compared to dogs, the differences between breeds must be clearly worded so that it is not taken to an extreme.  Quite a challenge.

How to proceed? 

The following is for each breeder to use as a means of evaluation of their cats and the breed in general.

1. Select the ideal.   Even this is controversial with many looks to the Asian leopard cat and many breeders wanting to go with a larger cat and have it look more like a leopard or jaguar.    But each of us can consciously select our ideal...

2. Realize what is lacking.  This is the point of departure… it is not unusual for breeders to become “cattery blind.”  Cattery blind thinking goes something like “if you do not agree with my assessment you are an ignorant fool.”   (If you hear this sort of dialogue going on in your head…  reevaluate your position!)   There are check and balance ways to do this:

3. Set a main hypothesis.  Mine is.  “Breeding cats that seek to be around humans will produce cats wanting to be around humans.”

4. Decide how to evaluate this hypothesis.   Use criteria that allow a scientific method. In this scenario  a scale of 1-10 is used to allow  evaluation of the cats and kittens.

By noting the score, that is being very conscious of the individual kitten and how it was reacting, evaluating the kitten, it became clear what to begin selecting for in the kittens and in the parents.  It is all a matter of being conscious of what selection is based on... be aware.

The three generation model of selective breeding

The general accepted rule in genetics is that it takes three generations of selectively breeding for a trait to see it in place.  Three generations of breeding before the genetics are stable (homozygous) enough to be  reproduced.   This is based on the assumption that we breed selectively.  In order to work with selective breeding it follows a 3-generation rule.   You do not know what a particular line carries until you have the third generation… The Bengal cat is unfolding so quickly that we do not do this often… as a rule we are using young unproven cats and genetics.   I will show the model that is used to determine and create some homozygous individuals.   

The model I use is one found in the Book of the Cat, by Michael Wright (page21).  He uses the example of simple color genetics involving the dominant full density (D = full density) to the recessive blue. (d = dilute).  This trait is located on a particular locus in the chromosomes.   This example shows how to breed for a recessive trait making it homozygous.  Since the dilute gene does exist in the Bengal cat breed coming from the domestic genes, it is something that most breeders are working to breed out.

The full color density phenotype⁴  could also be Dd in the genotype⁵ . But we are assuming homozygous.

The full density parent can only give full density if homozygous.  DD        The dilute genes since it is also homozygous.  dd

Each kitten  receives a full density gene (D)        via the egg or sperm from one parent and a dilute gene (d)        from the other.  Because full density is dominant to dilute the result is a litter of heterozygous density kittens..   They are symbolized Dd       .  The starting point in any breeding program is called the parental or P generation; the first generation offspring are known as F₁  or first filial generation.  (The confusion of F generation that comes from the Asian leopard cat crosses is not being referred to here...  we are now talking straight cat genetics, not Bengal cat jargon of F1)

F₁  or first filial generation

Crossing heterozygous full density cats from the F₁  generation to each other, results in far more possibilities in the F₂ or second filial generation.  Each parent may pass on either the dominant black or the recessive blue gene, these combine randomly to create : homozygous black kittens (DD), heterozygous black kittens (Dd) and homozygous dilute kittens (dd)       .  The four possible combinations of eggs and sperm are all equally likely, and this is why, on average there will be three full density appearing offspring to one dilute blue.        

The only way to KNOW which is the genotype homozygous out of the three that appear in the phenotype to be the same...  is to breed the phenotype homozygous to the homozygous dilute and test breed or do DNA testing that is available for the A, B, C, and D locus. (see note at bottom)   

this is called Back crossing  BC

Back-crossing a heterozygous dilute cat from the F₁  generation to its homozygous recessive  dilute parent (P) Reveals the recessives in  the back-cross or BC generation.  The heterozygous dilute cat can pass on either the full density or the dilute gene, but the dilute parent can pass on only the recessive dilute gene.  Therefore the offspring can only be homozygous dilute (blue) or heterozygous density, like their parents.  On average, as the diagram shows, they will appear in equal numbers.  Back-crossing of this type has practical application for breeders in determining an individual’s genotype.     (The above is from page 21 in The Book of the Cat.)

In this case the ration for the phenotype and the genotype

If the BC was of the homozygous DD offspring to the homozygous dilute dd parent, all the off spring would be phenotypically full density, but in actuality be heterozygous.  But there would be NO dilutes to ever be produced by such a mating.  Because of random assortment of genes, the only way to be sure or moderately sure that the full density phenotype cat was indeed a homozygous one, is to have 9 offspring from this crossing.  Then one can be moderately sure, but there is a saying in feline genetics quoted from Don Shaw, a TICA judge and geneticist, "Recessives are forever."   Thus when a recessive is introduced, do so with great care! 

The is the model for a simple recessive.

Using this same model on other genetics: color, ears, temperament, whited bellies… allows for better selection of breeding cats.  Note:  many of the genetics are polygenetic so do not follow as simple a pattern… there are many other influencing factors.  However, this model is quite helpful in record keeping and in learning the basics of inheritance.

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