Stability of genetic parameter estimates for production traits in pigs

Changes in variance component estimates in growing sets of performance data in two pig breeds were Investigated. Data was used from the field and-stat ion test of Czech Landrace (LA: 75 099 observations) and the Slovakian bree d, White Meaty swine (WM: 32 203 observations). In LA the traits analysed w ere estimated lean meat content (LM) and average daily gain (ADGF) on field test and average daily gain (ADGS) and weight of valuable cuts (VCW) on st ation test. In WM the traits analysed were backfat thickness on field and s tation test (BFF, BFS, respectively), proportion of valuable cuts (VCP) on station test, ADGF and ADGS. Covariance components were estimated from four - and five-trait animal models using the VCE software. Omitting data from f actor levels with a low number of records led to 4.2% of LA records and 21. 7% of WM records being deleted. Changes in genetic and residual variance es timates were less than 5% for all traits in LA and less than 12% for all tr aits except ADGS in WM. The changes in estimated genetic variances caused b y 18 months (LA) or 24 months (WM) of new data were 2-25% and the changes i n estimated residual variances were than 5% in LA and less than 20% in WM. In both breeds, changes in heritability estimates did not exceed 0.06 in ab solute value. In LA, it is reasonable to use generic parameter estimates fo r 3 years before re-estimation. In WM the time interval should be shorter b ecause of changes in the estimates caused by their lower accuracy arising f rom the smaller size of the data-set and smaller frequency of station testi ng.