Genetic Abnormalities

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.

Structural Soundness

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.

Scoring format:
  1. Unacceptable (1-3 points). Severe structural problems that restrict the animal's ability to breed.
  2. Good (4-7 points). Animals with slight structural and/or movement problems.
  3. Excellent (8-10 points). No obvious structural or movement problems. (Includes even toe size, adequate length of stride, adequate flexion of hock and pastern cushion, trueness and freeness of movement.)

Underline Soundness

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 is justified.

Scoring format:

  1. Unacceptable (1-3 points). Fewer than six functional nipples on each side or one or more inverted nipples or poor spacing and prominence.
  2. Good (4-7 points). Six or more functionally nipples on each side with adequate spacing and prominence.
  3. Excellent (8-10 points). Six or more functional nipples on each side, well-spaced and well-developed with no pin or blind nipples.

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.