BREEDING & GENETICS PIH-9
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Boar Selection Guidelines for Commercial Pork Producers
Authors:
Allan P. Schinckel, Purdue University
Charles J. Christians, University of Minnesota
Ronald O. Bates, University of Missouri
Reviewers:
Erik Cleveland, University of Hawaii at Hilo
Donn Damos, North Henderson, Illinois
Lynn Cole, Mt. Blanchard, Ohio
Dave Elftman, Kokomo, Indiana
The performance level of the commercial swine herd is deter-
mined by two things: genetics and environment. The genetic con-
tribution is determined by the boars and gilts selected and the
crossbreeding program used. The environment, (weather, housing,
feeding, management, etc.) will enhance or hinder the genetic
expression of performance traits. The purpose of this publication
is to provide recommendations for selecting replacement boars.
Identification of Responsible
Seedstock Suppliers
It is extremely important that you identify seedstock sup-
pliers who can provide you with superior seedstock as a result of
their genetic selection and herd health programs. Identification
of progressive, responsible seedstock suppliers, is the only
means by which your herd can consistently improve its production
efficiency.
Genetic Improvement
The rate of genetic improvement in a commercial pork
producer's herd parallels the rate of genetic progress made by
the seedstock suppliers (Figure 1). To make significant genetic
progress for any economically important trait (growth rate, feed
conversion, carcass merit, or litter size), performance records
must be kept and superior animals selected to produce the next
generation.
The top three lines (A, B, C) of Figure 1 show the expected
improvement in genetic merit when the seedstock herds are making
genetic progress. The genetic merit of commercial herds follows
the progress made by the seedstock herds. In those seedstock
herds making genetic progress, the purchase of the highest-
ranking boars available, will enable the commercial herd to
approach the genetic level of the seedstock herd.
Purchase of boars from seedstock herds where genetic
improvement programs are not utilized (lines D and E) results in
inconsistent genetic progress. This is because the genetic merit
of the boars purchased is not improving.
Commercial herds which purchase average boars from geneti-
cally improved seedstock herds have an advantage over commercial
herds which purchase the very top boars from unimproved herds.
Average boars from genetically superior herds can be of higher
genetic merit than above average boars in genetically average or
below average herds. For this reason, identification of seedstock
producers is of primary importance. Selection of individual boars
from these producers is secondary.
When selecting seedstock suppliers, review their genetic
improvement program. A sound genetic improvement program should
include four features: (1) accurate, complete performance
records including animal identification, consistent measurement
of all boars and gilts (not on-again, off-again or limited, par-
tial performance testing), and ranking of animals within defined
contemporary groups; (2) assessment of the genetic merit of
economically important traits (growth rate, feed efficiency, car-
cass merit, and reproductive performance) based on the
individual's performance relative to its contemporary group and
incorporating the performance of relatives; (3) indexes weighting
traits relative to their economic importance in commercial pork
production (the indexes should correctly rank the individuals
relative to their intended use in crossbreeding systems); and (4)
selection of the highest-ranking boars and gilts based on selec-
tion indexes. Seedstock producers should utilize selection
indexes as their primary selection criteria. Some emphasis
should also be given to physical characteristics such as repro-
ductive and skeletal soundness. Refer to PIH-101 Selection for
Feet and Leg Soundness. Selection indexes are the most effective
means to improve a combination of economically important traits.
Seedstock producers who ignore performance records and selection
indexes realize only a small fraction of the genetic progress
possible as compared to producers who utilize indexes as the pri-
mary selection criteria.
For seedstock herds to make consistent genetic progress as
presented in Figure 1, they must use superior performance tested
boars either from their own herd or from other herds that utilize
sound performance testing and selection programs. Figure 2 shows
the expected increase in genetic merit in herds using differing
percentages of superior performance tested boars. If the seed-
stock producer selects his own replacement gilts but purchases
boars from unimproved herds, very little genetic progress is pos-
sible. If the seedstock producer uses only 25 to 50% of the supe-
rior performance tested boars while also using boars of poor or
unknown genetic merit, little genetic progress is possible. By
compromising his selection program and using boars from producers
who have not selected superior boars themselves, genetic progress
is drastically reduced.
A commercial pork producer cannot expect the genetic merit
for economically important traits in his herd to consistently
improve unless the seedstock producer uses superior performance
tested boars. Therefore, commercial producers should purchase
seedstock from suppliers who use exclusively superior performance
tested sires and are selecting superior replacement gilts.
Seedstock Herd Health
Identify seedstock producers that have implemented
comprehensive herd health programs. A comprehensive herd health
program includes a veterinarian that makes routine onfarm inspec-
tions, conducts blood tests and other diagnostic procedures,
examines animals, counsels and makes recommendations. The seed-
stock supplier should minimize opportunities for new disease
organisms to enter the herd by using blood testing, isolation of
herd replacements, strict traffic control and sanitation. The
management program should also include adequate nutrition, com-
fortable housing and ventilation, and vigorous parasite control.
Buy seedstock from herds whose health is superior to your
own herd's. Reputable breeders can clearly define the health
status of their herds and should be willing to have you or your
veterinarian contact their veterinarian to answer any questions.
The merits of minimal disease (e.g., SPF) breeding stock should
not be underestimated.
Considerations When Choosing Boars
Breed of BoarThe crossbreeding program used will likely dic-
tate the breed of boar. About 80% of boars are purchased from
purebred breeders and 20% from commercial breeding organizations.
Both can be good sources of replacement boars. Keep in mind that
offspring performance in crossbreeding programs is maximized when
``breeds'' and ``crosses'' are used in a systematic manner. For
more information on selecting breeds and crossbreeding systems,
see PIH-39, Crossbreeding Systems for Commercial Pork Production.
Age of BoarSelect and purchase boars at 6 to 7 months of age
for use after they reach 8 months of age. Don't use young boars
just because they appear to be large enough. Replacement boars
should be purchased at least 2 months prior to the breeding sea-
son. This allows them to be isolated and checked for health, con-
ditioned to the farm, and test-mated or evaluated for reproduc-
tive performance.
Performance RecordsWhen selecting boars on the basis of per-
formance records, consider those in the top 50% of the contem-
porary group. The seedstock supplier should explain how the boars
were ranked including the traits used in developing the ranking
or index value. The seedstock supplier should also describe the
criteria used to establish price categories. In general, the
highest-ranking available boar is justifiable when he is expected
to sire a large number of progeny and/or produce replacement
gilts.
For rotational breeding programs, select boars on maternal
traits as well as growth rate, carcass quality (backfat), and
efficiency of gain. In specialized breeding programs where termi-
nal sires are used, selection efforts should be based on boars
that will sire fast growing, efficient pigs with desirable car-
casses.
Maternal boars used to produce replacement gilts for termi-
nal crossing programs should be selected on a balance of repro-
ductive and postweaning performance. Reproduction traits are
important, as a maternal sire can produce many replacement gilts.
Growth rate, carcass merit and feed efficiency are important as
the maternal sire will produce barrows and unselected gilt
offspring. Also, selected daughters will transmit one-half of
their genetic merit for postweaning traits to many terminal cross
market hogs.
Performance PedigreesPerformance pedigrees are a listing of
the animal's ancestors with their performance and genetic evalua-
tions. Performance pedigrees can document consistent performance
testing and selection.
Economic Implications
Commercial pork producers should be willing to pay a premium
for genetically superior, healthy seedstock, because of the
resulting improved pork production efficiency, and to offset the
seedstock producer's performance testing and health program
costs. Support of seedstock producers who have comprehensive
genetic improvement and herd health programs will allow continued
genetic progress and improved performance. This will enhance your
survival in a competitive market place and lead to a more effi-
cient pork industry.
Selection Facts to Remember
o For long term genetic improvement for any economic trait,
performance data must be collected and superior animals
selected within seedstock herds.
o Improvement of seedstock herd performance by nongenetic
means, such as new facilities, improved rations or more
space per pig will not result in improvement of the
seedstock's genetic merit or commercial progeny performance.
o Performance records from different herds do not allow an
accurate assessment of genetic differences. Differences
between performance levels of different herds are primarily
due to management differences.
o Comparisons are more accurate when individuals are compared
to other animals in the same contemporary group. Within a
contemporary group, all animals should be treated as uni-
formly as possible, for example, the same pen space and
diet.
o Performance testing does not result in genetic improvement.
Genetic improvement occurs when seedstock herds select the
highest-ranking boars and gilts as replacements based on
performance data.
o Evaluate each potential seedstock supplier based upon their
performance testing and selection practices.
o When purchasing F1 boars, it is important to identify seed-
stock suppliers who have implemented genetic improvement
programs in the purebred lines. Performance testing and
selection within the purebred lines is the only means by
which the genetic merit and progeny performance of the
crossbred boars can consistently improve.
o Not all traits are expressed in boars, e.g., litter size,
litter weight, but are expressed in their female ancestors,
sibs, and offspring.
o Performance traits can be genetically correlated. For exam-
ple, selection of the faster-gaining, leaner boars and gilts
will result in a correlated response for improved feed effi-
ciency.
o Genetic evaluation programs (STAGES or Estimated Breeding
Value programs) will potentially allow more rapid genetic
progress by incorporating each individual's performance
records with available records of sibs, ancestors and pro-
geny. The accuracy of these evaluation programs declines as
the percentage of animals tested declines. Testing a lim-
ited sample of the herd yields inaccurate, possibly biased
genetic evaluations.
REV 12/87 (5M)
Figure 1. Rate of genetic improvement in swine herds.
Figure 2. Expected increase in genetic merit with different per-
centage superior performance tested boars used.
% Figures are available in hard copy
______________________________________________
Cooperative Extension Work in Agriculture and Home Economics,
State of Indiana, Purdue University and U.S. Department of Agri-
culture Cooperating. H.A. Wadsworth, Director, West Lafayette,
IN. Issued in furtherance of the Acts of May 8 and June 30, 1914.
It is the policy of the Cooperative Extension Service of Purdue
University that all persons shall have equal opportunity and
access to our programs and facilities.
.