How To Select?
Article (c) and reproduced by kind permission of Libbie
Kerr - A-Kerr's Bengals
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:
- health
- temperament
- appearance
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.
- honest evaluation of cats for breeding programs
- open exchange of genetic issues both positive and negative of the breeding
cats
- disclosure of genetic problems when found
- accurate record keeping
Cat shows are designed to evaluate breeding stock and vigour. 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
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?
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:
- The diverse appearance of the Bengal cat, noted in body type, head type, and
coat type. Showing great genetic diversity and little agreement on how to
narrow the scope.
- The continued out crossing to the Asian leopard cat. Thus keeping the Bengal
cat from becoming a stable domestic breed.
We are extremely heterozygous2
.
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.
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...
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…
re-evaluate
your position!) There are check and balance ways to do this:
- Cat shows… you take the best example to judges, who look at the standard and
evaluate your cat on a 100-point scale. In reality, you are not competing
against the other Bengal cats; you are evaluated on the judge’s individual
interpretation of the stated ideal (standard) prototype of the breed. Now,
an interesting point is that this is done with written standards, not
through photos. If done through photos you have a completely different sort
of comparison… and an interesting change in the dynamic.
- Another way of identifying what is missing is to evaluate each breeding cat.
You can do this several ways, a method I use is to make my top priority
list, I have learned if I try to do everything at once it only leads to mass
confusion and becomes difficult to track. So, because it is my particular
favorite thing, I am going to put temperament as my selection criteria as an
example of "how to breed and select for a particular trait."
Set a main hypothesis. Mine is. “Breeding cats that seek to be around humans
will produce cats wanting to be around humans.”
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.
Noise: 10 was a kitten that did not respond to sharp loud noises other than
to briefly be on alert to 1 which was a kitten that hid when I entered a
room and would not come out at all.
| Noise evaluation... 10 being the least response and 1 being extreme
|
| 10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
Approachability: 1 point for running if approached, hides, and will not come
out… 10 approaches an extended hand with no hesitation. I evaluated:
strangers… children, adult… evaluated position of people… talking loud,
making a lot of gestures, to sitting and playing with toys of interest to
them.
| Main Care Taker: Approachability: 10 approaches extended hand, 1 flees
|
| 10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
| Family Member: Approachability: 10 approaches extended hand, 1 flees
|
| 10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
| Loud Stranger: Approachability: 10 approaches extended hand, 1 flees
|
| 10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
| Children: Approachability: 10 approaches extended hand, 1 flees
|
| 10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
Another consideration was the scoop able test… if I reached down and scooped
them up did they immediately want to be put down or wait for me to place
them.
| "scoop able" test... 10 easily scooped up and held in arms no squirming, 1
wanted nothing to do with being held. (again, varies with individuals...
main care taker, stranger, etc.) |
| 10 |
9 |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
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.
- Full density = D- (the - indicates an unknown, but for this purpose we are
going to use homozygous density of DD) Shape color = gene
- dilute density = dd
The full color density phenotype3 could also be
Dd in the genotype4 . But we
are assuming homozygous.
| This is the PARENT GENERATION: P
|
Full density parent
dilute parent
|
D |
D |
| d
|
Dd |
Dd |
| d
|
Dd |
Dd |
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 |
| Each parent is heterozygous |
D |
d
|
| D |
DD |
Dd |
| d
|
Dd |
dd |
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)
- 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.
phenotype is: 3:1 ratio appears to be the same as in the phenotype... thus
three full color in appearance to one dilute.
genotype is 1:2:1 ratio : 2 :
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.
| This is called Back crossing BC |
parent is heterozygous for density
parent is homozygous for dilute |
D |
d
|
| d
|
Dd |
dd |
| d
|
Dd |
dd |
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
2:2 :
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 assortment5 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.
-
1 Homozygous: Having an identical pair of alleles for a particular
characteristic. Hypothesis: an assumption made in order to test its logical
or empirical consequence.
-
2 Heterozygous: Having a pair of dissimilar alleles, one from each parent, for
a particular characteristic.
-
3 Phenotype: An individual’s actual physical characteristics – size, shape,
eye color, hair length and so on – representing the physical expression of
its genotype.
-
4 Genotype: The set of genes an individual inherits from its parents.
-
5 Random assortment: The set of genes given from a parent are done so
randomly. Thus a litter of kittens may exhibit only one of the genes carried
by the parent and not another, thus recessives do not always reveal
themselves.
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