BREEDING & GENETICS                               PIH-9


       Boar Selection Guidelines for Commercial Pork Producers

Allan P. Schinckel, Purdue University
Charles J. Christians, University of Minnesota
Ronald O. Bates, University of Missouri

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

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

     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

     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-

     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

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-

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

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