By Mark Knauer and Jeff Wiegert, North Carolina State University; Chelsey Van Genderen, U.S. Pork Center of Excellence
Selecting replacement gilts with proper feet and leg soundness is important for pig farm profitability. At the sow farm, good structural conformation allows females to better compete in group housing situations and enhance sow herd retention. During the grow-finish phase, offspring from replacement gilts with good feet and legs will result in a greater percentage of full-value market hogs sold.

While feet and leg soundness is generally subjective, there is science behind “ideal” structural conformation. The side view of the front leg has been shown to impact sow longevity by multiple authors (Barczewski et al. 1990; Grindflek and Sehested, 1996; Jorgensen, 1996). In those studies, gilts with buck-kneed forelegs had poorer sow longevity when compared to gilts with better angularity to the front knee and pastern. The side view of the rear leg has also been associated with sow retention. Both Barczewski et al. (1990) and Ringmar-Cederberg et al. (1999) reported weak rear pasterns were correlated with enhanced sow longevity. Rib width is another trait shown to have favorable relationships with sow retention. Barczewski et al. (1990), Knauer et al. (2011) and Nikkilä et al. (2013) reported gilts that were wider through the center part of their rib cage had better sow longevity than narrow based gilts.

Knauer et al. (2009) reported structural conformation traits were favorably related. In other words, gilts with good locomotion were more likely to have a satisfactory front leg side view, rear leg side view, front view, rear view and rib width. These favorable associations may allow farmers to select gilts based on one or few structural conformation traits. Serenius et al. (2001) and Knauer et al. (2009) reported high genetic correlations between locomotion and front leg side view. Hence it may be possible to select replacement gilts for structural conformation based primarily on front leg side view, avoiding animals that are buck-kneed or straight in the front pasterns.

Identifying animals with good structural conformation can be challenging. Hence we have put together an instructional video to help farmers, and livestock judges of all ages, evaluate gilt structural conformation. The video is available through the U.S. Pork Center of Excellence at PorkGateway.org or YouTube. Further printed tools, including selection posters and a gilt evaluation pocket guide, are available through Pork.org.

Skeletal conformation and locomotion will continue to play an important role in animal well-being and pig farmer profit. However, the objectiveness of structural soundness traits must increase. New objective measures of structural and locomotion traits should be developed to aid farmers.

Contact Mark Knauer with any questions. 

Authors would like to acknowledge the U.S. Pork Center of Excellence for funding the video.

References

Barczewski, R. A., E. T. Kornegay, D. R. Notter, H. P. Veit, and M. E. Wright. 1990. Effects of feeding restricted energy and elevated calcium and phosphorus during growth on gait characteristics of culled sows and those surviving three parities. J. Anim. Sci. 68:3046-3055.

Grindflek, E., and E. Sehested. 1996. Conformation and longevity in Norwegian pigs. Pages 77-84 in Proc. Nordiska Jordbruk. Foren. Sem. 265- Longevity of Sows. Research Centre Forulum, Denmark.

Jorgensen, B. 1996. The influence of leg weakness in gilts on their longevity as sows, assessed by survival analysis. Pages 95- 100 in Proc. Nordiska Jordbruk. Foren. Sem. 265- Longevity of Sows. Research Centre Forulum, Denmark.

Knauer, M. T., M. T. See, J. P. Cassady, and D. W. Newcom. 2009 (Abstr.). Estimates of variance components and genetic correlations between swine structural conformation traits. J. Anim. Sci. 87(E-Suppl. 3):10.              

Knauer, M. T., J. P. Cassady, D. W. Newcom, and M. T. See. 2011. Phenotypic and genetic correlations between gilt estrus, puberty, growth, composition, and structural conformation traits with first litter sow reproductive measures. J. Anim. Sci. 89:935-942.

Nikkilä, M. T., K. J. Stalder, B. E. Mote, M. F. Rothschild, F. C. Gunsett, A. K. Johnson, L. A. Karriker, M. V. Boggess and T. V. Serenius. 2013. Genetic associations for gilt growth, compositional, and structural soundness traits with sow longevity and lifetime reproductive performance. J. Anim. Sci. 91:1570-1579.

Ringmar-Cederberg, E., N. Lundeheim, L. Rydhmer, K. Andersson, M. H. Yazdi, and Y. Le Cozler. 1999. Conformation scoring of gilts at 100kg and the relation to culling of the sow. Thesis., Swedish Univ. Agric. Sci., Uppsala.

Serenius, T., M. L. Sevón-Aimonen, and E. A. Mäntysaari. 2001. The genetics of leg weakness in Finnish Large White and Landrace populations. Livest. Prod. Sci. 69:101-111.