Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2008
Publication Date: 8/1/2008
Citation: Holl, J.W., Rohrer, G.A., Shackelford, S.D., Wheeler, T.L., Koohmaraie, M. 2008. Estimates of genetic parameters for kyphosis in two crossbred swine populations. Journal of Animal Science. 86:1765-1769.
Interpretive Summary: Production practices dispose of pigs with back or spinal abnormalities early in their lives. However, a defect in the curve of the spine was observed in pig and sow carcasses from two swine populations, where no visual evidence was present in live animals. Affected pigs potentially make the processing of pork loins more difficult and could decrease the value of the carcass. Pigs were measured for production, carcass, and structural traits and loins were scored for the spinal defect. Analyses provided evidence for a moderately heritable component to the condition and low correlations with other traits. Therefore, selection against the defect should be effective and not adversely affect other traits.
Technical Abstract: Genetic parameters for degree of kyphosis were estimated from a Duroc-Landrace F2 population (n = 316) and from a composite population (Line C) composed of Duroc, Large White, and two sources of Landrace (n = 1,552). Live presentation did not indicate kyphosis in pigs or sows. Degree of kyphosis was measured by scoring the shape of the vertebral column of split carcasses on a scale from 0 (normal) to 3 (severe). Of the animals slaughtered, 75.6% and 68.9% were normal, 11.1% and 23.3% were mild, 11.1% and 6.2% were moderate, and 2.2% and 1.5% were severe in F2 and Line C, respectively. Using linear models, fixed effects of age, sex, number of ribs, number of lumbar vertebrae, number of nipples, carcass length, and hot carcass weight, were not significantly associated (P > 0.10) with kyphosis score. Using an animal model, estimated heritabilities for kyphosis score were 0.30 and 0.32 in F2 and Line C, respectively. Estimated genetic correlations between kyphosis score and number of ribs, number of lumbar vertebrae, number of nipples, carcass length, and hot carcass weight were 0.05, -0.13, 0.00, 0.05, and 0.03. Selection to decrease kyphosis should be effective and not affect the number of ribs, lumbar vertebrae, nipples, or carcass length. In addition, selection for growth should not affect the incidence of kyphosis.