Estimates of Additive and Dominance Genetic Effects for Sow Longevity
Iowa State University Animal Industry Report 2006. The purpose of current study was to estimate variance components, especially dominance genetic variation, for overall leg action, length of productive life, and sow stayability until third and fifth parity. This project evaluated the data from Finnish litter recording scheme. The variance components were estimated in two purebred (Landrace, n=23,602 and Large White, n=22,984) and crossbred (Landrace x Large White, n=17,440) datasets. The fixed effect of herd-year, and random effects of additive sire, parental dominance, and litter were included in the statistical model of all the traits. Moreover, the fixed effect of breeding consultant, and linear regression of test weight were also included in the statistical model for overall leg action. The estimated heritabilities of these traits ranged between 0.04 and 0.06, and were very similar between the different breeds. Similarly, the estimates for ratio of dominance variance to phenotypic variance (d2) varied between 0.01 and 0.17, the highest from the crossbred dataset. Moreover, all the d2 estimates in crossbred population were higher than the corresponding heritability estimates. However, in purebred populations, d2 estimates were generally lower than the corresponding h2 estimates. All the genetic correlations between same traits from purebred and crossbred were high. This indicates that the genetic gain in purebred populations will be passed on to the commercial crossbred sows. Based on current results, we suggest considering accounting for the effect of dominance in the breeding value estimation of sow longevity, especially when data from crossbred animals are included. Moreover, because dominance genetic variation for sow longevity exists, it should be possible to use that variation by planning the mating pairs to produce sows for commercial production.