American Pit Bull Terrier Gazette Vol44 I2 | Page 4

A Continued Look At Prepotent
Brood Stock in ADBA History
by Amy Greenwood-Dudar
In the last issue of the American
Pit Bull Terrier Gazette, I laid the
ground work of the significance of the
study of the “Prepotent” sire and dams
throughout the history of our breed. For
those first time readers of the Gazette
and as a recap let’s begin with the
definition of Prepotent. Prepotent is
defined as having exceptional power,
authority of influence, in terms of dog
breeding, a prepotent sire or dam, passes
on their traits to a large number of their
offspring regardless to whom they were
bred. The value of both a prepotent
stud dog or brood matron can not be
understated, but the far reaching effects
to the breed as whole is greater in the
case of a prepotent stud dog. This is due
to the large number of offspring that can
be produced by a stud dog, compared to
that of a brood matron.
A review of the literature outlined the
genetic basis of prepotence: Jay L. Lush
stated in his book Animal Breeding
Plans, that the most important genetic
basis of prepotency depends first on
homozygosity ( alleles being the same
at a given gene), then upon dominance,
linkage and epistasis. A homozygous
animal possesses the gene for a given
trait from both his sire and dam and is
genetically pure for that characteristic.
Because the gene pairs are identical, this
gene is passed on to every one of their
offspring 100% of the time.
A dominant gene is described as one
of a pair of alleles (alternate forms of
the same gene influencing the same trait
but in different ways) whose effect is
expressed over the effects of the alternate
alleles. Every puppy receiving the
dominant allele will show the effect of
it. If the parent is homozygous for it, the
offspring will all be exactly alike for the
trait expressed by the gene, regardless of
the genetic material that they received
from the other parent. Lush states, when
a parent having many dominant genes is
also highly homozygous, its prepotency
is MAXIMUM.”
Linked genes are those that are located
closely on the same chromosomes.
Two or more characteristics are passed
on together instead of randomly in the
4
usual manner.
Epistasis is defined as when a gene
or a pair of allelic genes masks the
expression of a different gene or pair
of allelic genes. Epistasis is similar
to dominance except the relationship
is between different genes, instead of
alleles on the same genes. Because of
its similarity to dominance epistasis is
believed to contribute to prepotency.
Since Lush states, “the most
important genetic basis of prepotence
is homozygosity”, the next question to
be answered is how does the breeder
produce homozygosity in his breeding
stock?
Production of prepotent animals:
Even though we see prepotent brood
stock in lines that are not closely line
bred and inbred, the breeder’s chief
aid in producing a prepotent animal
is through the use of these breeding
strategies. The reason for this is that
while dominance, linkage and epistasis
of genes are not within the power of
the breeder to control, he CAN control
the homozygosity of his stock. The
more closely related the sire and dam,
the more rapid will be the increase
in homozygosity. Mating like to like
without inbreeding and line breeding
does little to increase prepotency.
“The broad scientific definition is that
inbreeding is the mating of animals more
closely related to each other than the
average relationship of the population
concerned.
When done properly and wisely it is
of great assistance and using inbreeding
vigorous prepotent animals of correct
type are more rapidly produced.” (Lush)
Because of this statement, I believe that
Lush is lumping styles of line breeding
together with classic styles of inbreeding
and refers to them all as inbreeding. He
states that the mating of brother to sister
is the highest form of inbreeding.
Inbreeding does not create any
weakness, defects or any of the physical or
mental traits which will disqualify a dog
from fulfilling its function. Inbreeding
merely exposes hidden recessive genes
that have been present in the stock all
along under the shield of their dominant
alleles. It does this by presenting them
in a homozygous condition so they are
expressed and made visible. By using
inbreeding, the breeder is given an
opportunity to discover exactly what
heredity traits are carried by his animals.
By bringing them to light, in some cases
he can completely remove from his
bloodline those individuals that prove
to be undesirable. Genetically purer
lines are the result from which desired
dogs may be selected, producing a truer
breeding strain. “Inbreeding with careful
selection has resulted in living, vigorous,
fertile lines even after many generations
of brother/sister matings”. (Snyder)
Another aspect of the value of
inbreeding is that some desired traits
in a breed may be due to recessive
genes rather than dominant ones. By
increasing the homozygosity of these
wanted recessives as well as the wanted
dominants, animals within the strain
can be made to breed true for these
characteristics also. The success of a
program of inbreeding depends upon
the skill of the breeder and the careful
selection and rigid culling of the breeding
animals, based upon what they are able
to produce (their genetic makeup) rather
than appearance alone.
The success of a breeding program
using inbreeding and close line breeding
as the breeding strategy will depend
upon the heredity nature of the individual
animals themselves. Those possessing
fewer genes for undesired traits (both
hidden and apparent) need less severe
culling and can be more closely inbred
without the appearance of defects than
those strains with many and varied
“skeletons in the closet”.
In the production of prepotent brood
stock, the wise use of inbreeding and
close line breeding can not be overlooked
and the action and results of this breeding
strategy are better understood today.
With the understanding of the
breeders opportunity and role in
producing prepotent brood stock, let’s
continue to look at the background of
some of prominent stud dogs in APBT
history and see how they measure up
to breeding strategies proposed in the