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EPD's: The Path to Alpaca Excellence
By Mike Safley
EPD’s: The Path to Alpaca Excellence
Northwest Alpacas www.alpacas.com Phone 503-628-3110
At first blush, animal breeding seems relatively simple. If you
believe "like begets like" all you need to do is
mate similar animals. If you want a further edge up - study pedigree.
If that is not good enough, you can measure phenotype making sure
only the best are included in your breeding plan. The problem is
none of these strategies is particularly effective, and many of
the beliefs that breeders rely on are black magic. Myth makes the
animal improvement equation more complex than it need be. Before
we can get on to steady measurable improvement, we must sweep a
few myths out of the closet. One of the more pervasive myths in
the alpaca industry is,"The best way to select elite breeding
stock is by analyzing their phenotype." It is closely followed
in importance, by the myth that "pedigree equals breeding value."
I think is it is fair to say that breeders faith in pedigree often
takes on mythic proportions, but their faith is not born from the
science of genetics. But, before I get to that we need to critically
analyze the role that phenotype and pedigree play in breed improvement
programs.
Phenotype is at least 50% environment, nurture and husbandry. Add
that to Mendel's laws of inheritance, which states that dominant
genes express themselves and recessive genes hide from view, and
you begin to understand why phenotype is a poor guide to breeding
value. If we are to breed for elite alpacas, we must have a dependable
method of determining which animals will pass on superior traits
in predictable fashion. Simply analyzing an alpaca's phenotype as
a guide to the animals breeding value is an entirely ineffective
improvement strategy. It is a fact that assessing an alpaca's phenotype
to determine its breeding value is the least reliable method of
selection.
Pedigrees document ancestors beautifully but are only of marginal
assistance when being used to identify alpacas that will breed true.
The great-grandsire of any given alpaca contributes 1/8th of his
genes to the total genetic makeup of the grandson. Selection based
on pedigree as the sole selection criteria, assuming a 30% heritability
factor, is from 38 to 55% accurate (Understanding Animal Breeding,
2000, Richard Bourdan). This means if you use the pedigree to make
breeding decisions you will be right about 50% of the time. When
you add the measurement of individual phenotypic traits — records
for fleece density, micron count, staple length and so on-- to your
analysis the accuracy of selection increases to about 65%. However,
if you add the production records of the parent's progeny to the
analysis your ability to predict improvement increases to near 100%.
There is simply too much that a pedigree does not tell you about
an alpaca.
The critical flaw in using pedigree to select and breed alpacas
is that the information most useful to the breeder, from a genetic
improvement perspective, is not on the pedigree. ARI pedigrees 1)
do not record an alpaca's phenotypic performance statistics; 2)
do not identify siblings or progeny; and 3) do not identify prepotency
or breeding value. Relying on a pedigree as an effective way to
select superior breeding stock is based more on myth than fact.
Craig Wheaton-Smith made the following observation about the use
of pedigree in his book Breeding Better Cows (1957).
MAKING USE OF PEDIGREE
"As things stand the vast majority of our dairy stock are sired
by unproven bulls, and quite a few are by bulls proved to be bad
(if the proof were fully available) the deficiency of merit being
well compensated for by sales technique and management". "Bulls,
then, sold on their pedigrees and widely used before their merits
are known, place considerable obstacles in the way of breeding from
only the better half of the population".
Wheaton-Smith is not the only one to point out the problems associated
with using pedigree as a selection tool. The renowned geneticist
Dr. A. L. Hagedoorn had this to say about the value of pedigree
in the fourth edition of his famous text, Animal Breeding:
"The faith in a beautiful pedigree is often astonishing."
I remember how the Dutch agricultural press wrote about the "breeding
value" of a bull sold to a Japanese delegation, in terms that
made one
think this must have been a bull proven by long lists of exceptionally
good daughters. It was said to be a pity that such bulls were sold
to foreigners. When the article went on to state that the bull was
ten months old, one wondered about the faith Orientals still seem
to have in ancestry. Pedigrees can be helpful in locating relatives
of families known to have high breeding values for certain traits,
and the higher the heritability factor for the trait being selected
for, the more one can rely on the ancestor's presence in the pedigree.
But, the truth of the matter is that the only accurate way to determine
the breeding value or dominance of a particular parent is to research
their progeny.
PERFORMANCE RECORDS
Before we proceed to a discussion of progeny testing, a word about
performance records.
The primary reason that an animal breeder keeps performance records
is to track the breeding value of a given dam or sire. In the alpaca
business, these records are most often used to promote a specific
animal's quality. You may have noticed the extensive use of a herdsire's
histogram to hype the claim that he is potent and wonderful, simply
based on his micron count. An astute observer might also notice
that in successive ads, published over a period of time, the micron
count never changes. This is physiologically impossible and, aside
from being a misuse of the performance record, it should serve to
make the point that one can't always believe the claims of a herdsire's
potency offered by an owner. The idea of a "proven" stud
is often misunderstood. Many people take the term to mean that the
stud has simply sired a number of defect-free offspring. When a
geneticist or a knowledgeable animal breeder uses the term, they
mean that the sire has "proven" that he can consistently
pass his positive production traits onto his progeny. In other words,
he has a high breeding value.
PROGENY TESTING
To make accurate selection decisions about your herd, you must be
able to assess the breeding value of a given alpaca – whether
or not it will pass its genotype and phenotypic superiority on to
its offspring. To assess a sire's breeding value, you must know
how many cria it has and how consistently they express the parent's
phenotype. In other words, you must progeny test. A geneticist tells
the animal breeder that they must assess the progeny of a given
ancestor before deciding if the ancestor is the appropriate sire
or dam for a large number of their cria. A progeny test, involves
multiple matings of an individual animal with a measured evaluation
of its offspring that helps predict that individual's breeding value.
Progeny testing for alpacas involves using a phenotypic evaluation
form to evaluate the phenotype of a stud's offspring for such important
traits as, fleece weight and fineness. Other heritable traits such
as size and bite can also be scored. The records that are gathered
on phenotype evaluation forms or from the breeder's production,
records become the basis for establishing Expected Progeny Differences
(EPD's). EPD's allow the comparison of breeding values between multiple
herdsires.
PROGENY TESTING AND HERD IMPROVEMENT
The most important decision any breeder makes is when they select
the male that will breed their females. The next most important
decision is when they select a replacement male. Once progeny testing
is used to evaluate several males, breeders can select the superior
animal as a stud and avoid using the males with low breeding values.
The males chosen by progeny tests will have higher breeding values.
In this manner, the herd's quality will quickly compound. Breeders
who incorporate the information gleaned from progeny testing into
their mating decisions will experience a steep improvement curve
within their herd. The myth that "pedigree equals breeding
value," or that, "the best way to select breeding stock
is by analyzing their phenotype" will cease to be a roadblock
to improvement. The increased quality, herd wide, will quickly compound
and be reflected in fleece weights, fiber fineness and other quantifiable
economic and conformation traits. The additional gain made over
three to four generations will be dramatic. There are several factors
which inhibit the ability of breeders successful deployment of the
factors described above. They include small average herd size, a
poor central record-keeping facility, lack of shared records, and
lack of access to progeny tested males.
PREREQUISITES FOR IMPROVEMENT
There are four general industry prerequisites for rapid, breed-wide
alpaca improvement.
1. Breeding objectives: There needs to be goal of excellence which
focuses primarily on heritable, commercial traits;
2. Performance evaluation: There needs to be a central record keeping
system established that measures and records performance for specific
commercial fleece characteristics. These records form the basis
for establishing heritability estimates for specific characteristics
and expected progeny differences (EPD's) for specific animals.
3. Breeding systems: There needs to be mating systems established
that maximize the rate of genetic gain in a predetermined direction.
4. Pedigree records: Clear, accurate records of ancestors should
be recorded and available.
DRAMATIC GENETIC IMPROVEMENT
There are also four basic genetic prerequisites for rapid breed
improvement:
1. genetic variability
2. selection intensity
3. selection accuracy
4. generational interval
Genetic variation is extremely important to the rate of gain. The
more variation for a particular trait in a population, the more
potential there is for change. If breeders have a wide variety of
animals to choose from – such as those with high or low fleece
weights – they can select alpacas with high fleece weight and
breed for the trait. Improvement in fleece weight will be rapid.
Selection accuracy is important if any improvement or gain is to
be made. This means the traits you select for must be heritable.
Accuracy assumes that we have the ability to separate superior and
inferior animals. If you select for a heritable characteristic,
such as fleece weight, you must identify superior stud males who
historically have produced offspring with higher than average fleece
weights to insure the trait is passed to the offspring. The same
goes for fineness, crimp, staple length, etc. The single most effective
way to do this is by establishing EPD's.
Selection intensity means being highly selective of progeny produced
by the parents you have chosen for foundation stock, and retaining
in your herd only the offspring that exhibit a superior expression
of the trait under selection. This ensures that breeding values
will remain high and that each generation of offspring should improve:
The higher the selection intensity, the higher the rate of genetic
gain. Generational interval affects the rate of genetic change simply
because the more rapidly one generation replaces the previous one,
the faster the potential gain. Mice reproduce more quickly than
humans, producing 150 generations in the time it takes humans to
produce one. (This makes it much easier to effect change in mice
than in humans. And improving people is a problem because there
is very little culling undertaken.) Generational interval is determined
by the average age of the producing males and females in a given
herd. Alpacas have a generation interval of four to six years for
females and approximately five years for males,
although this interval will vary from herd to herd. The shorter
the interval the faster the gain. To construct an improvement model
that allows each of these principles to work efficiently with our
current industry organization, there needs to be a large group of
alpacas sharing performance records and genetics. Many small breeders
with smaller herds will, when acting together, out perform even
the largest breeder. The "how" is EPD's.
WHAT ARE EXPECTED PROGENY DIFFERENCES?
An EPD is an estimate of the genetic merit of an animal for a single
trait. The EPD is the expected difference between the performance
of a specific animal's progeny for a specific trait and the average
performance of all progeny for that trait.
CREATING AN EPD DATABASE
Alpaca breeders will need to record performance values for their
animals. This information can be posted via a web-based tool. Most
of the necessary information would be compiled from a histogram,
(Information graph) and then downloaded to the database. The data
from alpacas reared under many different management systems is combined
into one file. A computer software program (BLUP: Best Liner Unbiased
Prediction) then identifies the genetic linkages between the alpacas.
The dataset for the alpacas includes all the data from previous
years, for all the relatives, across generations. The EPD calculations
include data from related traits, because an animal's performance
in any trait gives information on how it will perform in a similar
trait (for example, fleece weight and staple length). These calculations
produce EPD values on every trait for every alpaca herdsire, dam
and cria in the system. And these EPD's are recalculated, annually,
after the performance records from each new production cycle is
entered into the database. EPD's are not constants; they are estimates
of genetic merit that change over time as new information accumulates
on an animal and its relatives. Thus each year results in a new
set of EPD's for all animals, with progressive increases in the
accuracy of the estimates and in the breeders ability to discriminate
among prospective breeding animals.
HOW ARE EPD's REPORTED?
An EPD is reported in the normal units for the trait, such as +0.75
pounds (for fleece weights) or -0.4 microns (for fiber diameter).
It's important to note that an EPD value is not a ratio or an index.
EPDs are expressed as deviations (+ or -) from the average population
value, which is considered to be zero. This average of the herd’s
performance, which is used to establish the baseline (zero) for
comparison purposes, might be recalculated periodically, probably
every five years. EPD's always have a positive (+) or negative (-)
sign in front of them. The positive and negative symbols don't always
mean better or worse--it depends on the particular trait. For example,
a fleece weight of +0.75 pounds is good (more fleece than the average
of the herd under evaluation) but a Fiber Diameter EPD of -0.3 microns
is also be good, i.e. finer fiber than the average. These EPDs are
used to compare herdsires, for instance, a stud with a fleece weight
EPD of +3.0 is good, but a different stud with a fleece weight EPD
of +4.0 is better. EPD's may take a little getting used to, but
once you get the hang of them, they give the most objective and
reliable estimation of genetic value possible. The calculation of
EPD's uses data from many different herds, and this procedure is
mathematically valid across herds, so long as none of the herds
is genetically isolated from the others. But the feed regimen at
all farms must be good enough to permit good performance.
ACROSS-HERD GENETIC EVALUATION
For cooperating breeders, the purpose of large-scale genetic evaluation
is not complicated: They simply want to compare the performance
of their animals to one another and those in different herds. Why
is this important? Suppose an alpaca breeder has what he or she
believes is the best stud male in the world. Without a method of
comparing this male's performance to that of other males in other
herds, the owner can never know the truth of their belief. Across-herd
or large-scale genetic evaluation allows the truth of excellence
to be proven and then shared. Almost as important as the EPD's of
excellent sires is the identification of underperforming animals.
The value of culling inferior genotypes cannot be overestimated.
Across-herd evaluation provides an honest way to assess an animal’s
potential, and this creates the opportunity for rapid genetic gain.
The process of evaluating individual alpacas through direct comparison
with alpacas in different herds enables cooperating breeders to
more accurately select from a more genetically diverse, yet increasingly
improved, gene pool.
THE VALUE OF EPD'S
Richard Bourdon makes the value of large scale evaluation clear.
"Just as it is easier to field quality athletic teams at a
big school than at a small school because the big school has more
athletes to choose from," Bourdon writes, "so it is easier
to find truly outstanding breeding animals in a large population
than in a small one." When a group of cooperating breeders
shares records by using a central database, they create, for themselves,
an enormous advantage. They control, for their collective benefit,
many times the information of a single breeder. In the animal breeding
business, this information is the key to success. When across-herd
data is gathered, the accuracy of prediction increases by the sheer
volume of the information available. The EPD's for the various sires
and bloodlines can be readily and accurately established.
People often ask me how long I believe the alpaca market will last.
In view of the fact that alpacas are one of the worlds oldest domesticated
livestock I think it is fair to say that there will be a market in
alpacas long after you and I are gone. I also believe that so long
as breeders see improvement and potential in the breed they will remain
passionate about alpacas. I have been raising alpacas for almost twenty-five
years and I am more excited about them today than ever before. Shortly
before he died, I asked Don Julio Barreda if he had any regrets about
spending his entire life raising alpacas,"No, he said, I only
wish I had another 50 years to spend with my herd." I hope, at
the end of the day, we all look back and feel the same.
EPD's: The Path to Alpaca Excellence
Northwest Alpacas www.alpacas.com Phone 503-628-3110
Fiber Characteristics of U.S.Huacaya Alpacas
By: Angus McColl, Chris Lupton and Bob Stobart
This informative study was conducted to establish
a comprehensive profile of U.S. Huacaya Alpaca fiber characteristics
that could be useful for educational, promotional, policy, selection,
and breeding purposes. 23 fiber characteristics and body weight
of a representative sample of US Alpacas were measured or calculated.
Compared to wool of comparable fineness, the Alpaca was shown to
be higher yielding, more heavily medullated (a distinctive feature
of Alpaca), longer, and considerably stronger. Resistance to compression
was invariably lower for Alpaca compared to wool of comparable fiber
diameter likely due to the lower levels of crimp in the Alpaca fibers.
Click here
to read the full article.
Original research conducted by Alpaca Research Foundation. Published
in Alpacas Magazine, Summer: 2-11 (2004)
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