reproductive
potential (as evidenced by their mothers’
reproductive record). These systems reduce out-of-pocket
breeding stock expenses since all replacement
females are home-raised.
However, the retention of gilts from all sires means
that all sires must be selected for superior genetic
potential for carcass (backfat, muscling), production (feed
efficiency, growth rate) and reproduction (pigs per litter,
milking ability) traits. Boars that are above average in all
three types of traits are not likely to be truly superior in
any one area.
Terminal breeding systems
involve crossing boar
lines selected strictly for carcass and production traits
with gilt lines that are selected mainly for reproductive
potential. These matings produce offspring that are all
marketed (therefore the name “terminal”), and no gilts
are retained for breeding.
Since terminal boars are selected without concern for
reproductive potential (remember that no gilts will be
kept from the matings), ones that are truly exceptional
for carcass and production traits can be used for
breeding. The same is true of gilt lines. Emphasis can be
placed on reproduction, with other traits being
important but secondary.
Gilt lines used in modern terminal breeding systems
involve mainly the white breeds – Yorkshire, Landrace
and Chester White. These breeds are generally superior in
reproductive traits, such as litter size, milk
production and docile temperament. Most terminal sire
lines use the colored breeds, which are generally more
durable (i.e. can withstand stressful conditions better)
and are leaner and heavier muscled.
A major change in the pork industry since 1980 has
been the shift from rotational to
terminal breeding
systems. This change was brought about largely by
pigpricing systems that explicitly reward leaner hogs and
penalize fatter pigs, as well as a more thorough
understanding of the economic importance of high
reproductive efficiency. Today, the majority of pigs in
the U.S. are produced from terminal breeding systems.
Many of the most modern pork production systems
have gone to a closed herd concept,
where all the
breeding females are produced in-house. Genetic
advances are made strictly through the use of boar
semen brought in from the outside. The major advantage of
this system is that it reduces possibility |
of introducing any new
diseases to the operation and thus enhances pigs’ heath
status.
Identifying superior boars has become easier with the
use of Expected Progeny Differences
(EPDs) for each trait on each boar. An EPD is the
expected amount by which a given boar’s offspring will
differ from the average of all animals in the population for
a certain
trait. So, the larger the EPD, the more superior the boar is
for that trait.
Both purebred breeders and breeding stock
companies use Best Linear Unbiased
Predictor
(BLUP) genetic evaluation software to identify
the
boars with the highest EPDs. BLUP software uses data from up
to 300,000 relatives of a given animal to
increase the probability that a selected boar truly
possesses genes superior to those of other boars in the
population. The use of BLUP software and EPDs has
contributed greatly to the rapid genetic improvement of the
U.S. swine herd since 1980.
Swine
Production Systems
Whether pigs are raised in pastures or in totally
enclosed barns, systems approaches dominate pork
production. Repeatable methods and specialization
characterize the modern pork producer regardless of
the type of facilities used.
The choice of facility type is mainly a balancing of
capital investment, labor requirement and management
expertise. Animal and worker welfare are primary
concerns to producers, regardless of the type of facilities
chosen. The key to good swine care rests more on the
producer’s ability to properly manage housing than it does
on the specific type of housing provided. |
