Sow herd mortality and culling rates have reached unacceptable levels in some herds. The attached poster is the first in a series developed to help pork producers more effectively screen replacement gilt candidates before placing them in their breeding herds.

The first poster in this series focuses on conformation and structural soundness. Whether purchasing replacement gilts or producing your own in an internal multiplication program, the poster shows examples of good and poor conformation and skeletal structure.

Structural evaluation is a process of visual appraisal by scoring or evaluating animals for proper skeletal structure and feet and leg soundness. Research has shown that certain structural conditions can affect a sow's lifetime performance in the breeding herd.

Visual appraisal can help identify replacement gilts with “buck-kneed” front legs, straight rear pasterns and swaying hips — all of which have been shown to negatively impact sow longevity.

Identifying replacement gilts with one or more of these conditions and culling them, rather than utilizing them in the breeding program, may be one of the keys to lowering breeding herd replacement rates and/or mortality rates.

In addition to the negative relationships between some leg abnormalities and longevity, research has also shown that some conformation traits have a positive effect on longevity. Specifically, soft pasterns on the front legs can be a favorable indicator of a sow's ability to remain in the breeding herd longer.

The pictures and diagrams will assist producers in identifying these conditions. Subsequent posters in February and March will focus on feet and leg soundness and reproductive trait (underlines, external genitalia) soundness, respectively.

More detailed information on the evaluation of swine for structural soundness, including a scoring system, is available from the National Swine Improvement Federation at

Heritability of Structural Soundness

Structural soundness has been shown to be moderately heritable, which means seedstock suppliers should be able to improve this trait through selection. Therefore, keep in mind that the traits contributing to structural soundness in a parent will also have an impact on their offspring.

For example, if animals with structural deficiencies (i.e., buck-kneed forelegs, straight or upright pasterns, etc.) are retained for breeding purposes, we would expect a significant number of their offspring to have this condition. Unsound animals do not perform as well as their more sound counterparts.

Additionally, unsound animals are more likely to pose problems during transportation and lairage at harvest facilities. This underscores the importance of structural soundness and its role in profitable pork production.

Environmental Factors

Many environmental factors also influence structural soundness. For example, nutrition, gender, health and level of production are factors. Housing conditions, such as degree of floor roughness, location of equipment and level of repair, pig density in all phases of production, and exercise can also influence structural soundness.

Many selection programs have largely ignored structural soundness in recent years, while more emphasis has been placed on other economically important production traits. Ignoring structural soundness has resulted in an increasing number of animals exhibiting one or more structural problems.

While producers may think that these conditions only rarely occur, the reality is that most operations can find one or more of these conditions within any group of replacement females.

The organizers of this project visited only three operations to find the vast array of structural imperfections used in this poster series. This reinforces how common many of these conditions are, and that no operation is free of all of these challenges.

When to Cull

It should be noted that not all animals have perfect structural and reproductive soundness. Any selection program must evaluate and prioritize the importance of numerous traits. Compromises are often made with the level of structural soundness, degree of muscling or fatness and other traits under consideration.

For example, should a gilt be culled because of a minor structural defect at the expense of leaving a farrowing crate empty? Probably not, but the important point is to recognize the consequences of retaining these animals.

Ask yourself: How will a defect affect an individual's productivity in the farrowing crate? How will it impact the productivity of her offspring?

This series of posters was produced through the cooperative efforts of Pork Checkoff, National Swine Registry, National Hog Farmer and Iowa State University Swine Extension.

Additional copies of the posters are available free to U.S. producers and agricultural educators. Non-producer and foreign poster orders are available at 50¢ each. Contact Pork Checkoff at (800) 456-PORK or visit the Pork Checkoff catalogue at The complete set of three posters will be available after March 15.