Accumulated inbreeding over several generations

Accumulated inbreeding over several generations.doc By Loren
Bolinger, 10/17/2001

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Accumulated inbreeding over several
generations

A tail-female bloodline, or matriline, composed of a series of
relatively-inbred broodmares from a successful matriline that
has reliably exhibited high levels of blacktype performance
(even if success is somewhat distant) has been performance-
sensitized. That is, genetic conditions have been constructed
(or set in place) that channel the forces of inheritance toward
continued winning performance from descendants from this
matriline. Mares descended from such a family will often
continue successful productivity of performance traits even
when bred to regional sires that are relative outcrosses,
provided that there is, at least, limited inbreeding within six
generations to a few key ancestors. Limited, near inbreeding
to prepotency is more effective when the distant strains in the
sire and dam are organized. Distant kinship is one of the
forces of inheritance successfully used by Bruce Lowe, both in
Australia for Frank Reynolds and others and with his
nineteenth century importations for James Ben Ali Haggins’
Rancho del Paso Stud in California.

Selection and mating of breeding stock related through distant
kinship is a great organizational tool that results in increased
expression of performance traits. As in other mating schemes,
selecting stallions that have already produced high quality
progeny and/or have exhibited the highest possible racing class
will increase the probabilities of producing successful progeny.
Mating breeding stock whose own phenotypes tend toward the
mean phenotype for their particular bloodline will reproduce
their bloodlines’ characteristics more reliably. Breeding
extremes to one another tends to be extremely unreliable and
genetically more variable. Stallions and mares should have
compatible phenotypes.

In planning matings for future progeny from relatively inbred
female families, the breeder should key off certain prepotent
selected ancestors in the pedigree of the broodmare. Even
with limited inbreeding to only a few key ancestors, mostly
outcrossed progeny from inbred broodmares can still express
performance traits. In other words, a small boost from
relatively limited reinforcement of only a few ancestors will
cause the re-expression of performance in these progeny
beyond the mean for the breed. Sire-candidates selected for
such broodmares even though near outcrosses, should have
distant kinship to the tail-female family of the broodmare.
While using six-generation hypothetical breedings (on paper or
the computer screen) to determine the feasibility of the mating,
extended 8 –10 generations or more will assist in assessing
distant relationships of the proposed mating.

It is more desirable, if at least two of the broodmares in the
first four or five dams of the tail-female series have relatively
balanced inbreeding within six generations. The accumulations
of relatively balanced inbreeding should occur in at least
several of the broodmares in the series (usually closer to the
target, better in the dam and the granddam). The breeder
should prefer reinforcements of duplicated ancestors within
six-generations that have built-up or accumulated in at least a
minimum of two dams.

Loren Bolinger
Running Horse Farm LLC
7102 Ilfield Road Southwest
Albuquerque, New Mexico 87105-7046
505-873-2220 Voice
505-877-4443 FAX
e-mail: lbolinger1@comcast.net

Fixing The Type

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FIXING THE TYPE
by Loren Bolinger, 2/27/04 - 3/3/04

How the early breeders fixed the type of the
Thoroughbred: Intermingled colateral matrilines, and
melded early Founder patrilines. How their
stewardship of the breed was so successful that today's
horsemen are still reaping the rewards of their
pioneering selective mating techniques. The science of
genetics has acknowledged and proved the validity of
many of the early techniques.

The breeder manipulated the genotype through selective
mating techniques, typically inbreeding and the
recognition and repetition of certain pedigree patterns.
The breeder selected and culled though evaluation of
the resulting offspring of the mating primarily through
phenotype measured by objective performance and/or
its relationship to performance.
Fixing the Type (establishing the typology)
The Thoroughbred horse is a hybrid breed that normally does
not breed true-to-type. The racehorse breeder attempts to
reduce the phenotypic volatility or variability in the racehorse
he breeds through employing mating strategies that increase
multiple instances of inbreeding or linebreeding over
successive generations, while culling out those individuals that
fail to meet expectations. Inbreeding reduces the number of
ancestors in a pedigree by duplicating those thought to be
more important or prepotent. By purifying the ancestry, the
breeder reduces the variability, hopefully to increase the
probability of breeding true-to-type.]

Fixing the type means to reinforce a family’s or strain’s
phenotype through selective breeding, heavy overall
inbreeding, and culling. The purpose of fixing the type is to
increase the permanence and stability of the genotype so that
the breeder can more reliably predict the phenotype and to
more reliably trigger the expression of performance traits in the
offspring resulting from selective matings. By increasing
stability of the genotype through careful reduction of the total
number of ancestors, variability of the phenotype can be
dramatically reduced. Selective breeding techniques have been
devised that attempt to more reliably predict and reproduce
desired inherited traits and characteristics in offspring from
selective matings without significantly increasing deleterious
possible side effects of inbreeding. Typology means the
phenotypic or physical characteristics that are manifested from
an offspring’s genotype and the environment with which it
interacts.
How Fixing the Type was Acomplished

Selective mating was accomplished through three general
strategies: Genetic Isolation - Differentiation [breeding toward
a desired goal] cannot take place unless no new genetic
material is introduced over a period of time. No additional
founder-type bloodlines were introduced, once the original
male and female Founder stock was chosen. Artificial
Selection - The breeder selects matings between individuals
exhibiting desired traits or attributes and avoids random
matings. Inbreeding - Inbreeding reduces diversity [weeds out
undesirable traits] while fixing or reinforcing desired traits.
In order to “fix type,” a breeder or several generations of
breeders must closely linebreed among the descendants of
several, selected, prepotent individuals that are complementary
to each other and in whom a high rate of successful offspring
are produced. In this way, the breeder concentrates the
successful and productive genetic assets of a family. The
breeder selects patterns that sex-balance the immediate
descendants of duplicated ancestors, selects mates in such a
way that patterns of inversion in their bloodlines-in-common
occurs along paternal and maternal wings, inbreed to great
mares and to great matrilines. The breeder selects prepotent
stallions from compatible bloodlines, and avoids, as much as
possible, excess male inbreeding while simultaneously
increasing inbreeding to females, and increases the overall
quality and quantity of matriarchs/great mares in the pedigrees
of the offspring. The above are some of the selective mating
strategies that lead to success. The final strategy, sometimes
emotionally difficult, is to cull for failure. Cull for failure to
perform, cull for deviation from phenotype. Selective mating
means to select mates based on the most reasonable
hypotheses and objectives concerning bloodlines, pedigree
patterns, and phenotype. Those that fail to live up to the
objectives should be culled from the selective breeding
program.
Pedigree Matching
Bloodlines colateral to each other share an important role in
the selective mating technique called pedigree matching, that
is, utilizing those bloodlines that developed in parallel with one
another. Pedigree matching means that ancestors of the
colateral bloodlines share kinship or relatedness with one
another through powerful ancestors-in-common. The hooks of
the key members of the colateral bloodlines were commonly
opposite-sex-balanced - ancestral links or hooks inverted by
sex from each other.

Loren Bolinger
Running Horse Farm LLC
7102 Ilfield Road Southwest
Albuquerque, New Mexico 87105-7046
505-873-2220 Voice
505-877-4443 FAX
e-mail: lbolinger1@comcast.net