|GUIDELINES FOR UNIFORM SWINE IMPROVEMENT PROGRAMS|
Any genetic defects should be noted and the ancestry of
the affected animal checked. PIH factsheet 97 contains information
on a number of known genetic defects.
Breeding animals must be structurally correct and mobile to carry out their normal functions. Limited research suggests soundness is at least moderately heritable. The following recommendations are offered as aids in selecting replacement animals. The animals should be evaluated at or near the end of test and prior to conditioning. Date of appraisal should be noted. Animals should be given a score of 1 to 5 for both front and rear leg conformation using Figure 2 as a guide. Front and rear scores should be summed for the final evaluation.
Sows must have functional nipples to rear pigs. The role and
heritability of spacing, prominence, location, etc., of nipples
in production has not been defined clearly by research. But,
because these traits may have a direct influence on production,
their consideration in live evaluation of boars as well as gilts
Porcine Stress Syndrome
Porcine Stress Syndrome (PSS) is an inherited neuromuscular disease
caused by homozygous recessive genes at a single locus. When
stressed, animals afflicted by this syndrome have splotchy coloring,
breathe heavily, exhibit tail tremors, and often die. Homozgous
PSS and heterozygous carrier animals should be identified as such
when merchandized as breeding stock.
Animals affected by PSS may be leaner and more muscular in appearance,
with an evident separation between the major muscles of the ham.
Affected animals surviving to slaughter are verly likely to produce
pale, soft and exudative (PSE), or dark, firm and dry (DFD) meat.
It is now possible to classify pigs objectively for PSS using
one of two tests. The first and most accurate test involves extraction
of DNA from tissues, generally blood, and its amplification by
copying. The amplified DNA is separated on an electrophoretic
gel and one of three banding patterns emerges that correspond
to either homozygous positive (nn), heterozygous carrier (Nn)
or normal negative animals (NN).
The second test is a bit more involved and requires some specialized equipment under the direction of a trained technician. In this test the pig is exposed to an anesthetic called Halothane. Animals that are the PSS type respond to the Halothane anesthesia by showing signs of extreme muscle rigidity within three minutes from the start of the treatment. Occasionally, an animal that does not respond within this brief period will respond to a longer treatment, but this is not often the case. NN and Nn genotypes do not respond and are not separable by this procedure.
Figure 2. Foot and Leg Structural Deficiencies.