Abstract:
Reproductive traits and on farm performance test records of Duroc, Landrace, Large white and Yorkshire sows from a government farm (Farm 1) and a commercial farm (Farm 2) of 2,224 sows which were culled during 1991-2001 were analysed. The sows included must have had at least one farrowing record and two piglets weaned. Total number of records after editing were 16,621. Genetic parameters for true longevity (TL), functional longevity (FL), lifetime total born (LTB), lifetime born alive (LBA) and lifetime number of piglets weaned (LNW) were analysed using restricted maximum likelihood (REML) based on multiple traits animal model. Heritability estimates for TL and FL were similar at 0.03 and 0.04 in Farm 1 and Farm 2, respectively. Heritabilities for LTB, LBA and LNW were estimated to be 0.16, 0.20, 0.13 and 0.17, 0.18, 0.12 in Farm 1 and Farm 2, respectively. The genetic correlation estimates between longevities and lifetime productivities ranged from 0.37 to 0.65 in Farm 1 and -0.14 to 0.25 in Farm 2. The phenotypic correlation between longevities and lifetime productivities were from -0.04 to 0.05 and 0.07 to 0.10 in Farm 1 and Farm 2, respectively. High genetic and phenotypic correlations among LTB, LBA and LNW of sows in two farms were found from 0.65 to 0.98 and 0.50 to 0.90, respectively. Small to zero genetic progress would be resulted from selection for TL and FL due to low heritabilities of the traits. Indirect selection of other conformation traits related to health, stature and reproduction such as legs, feet and udders as well as improving environmental conditions might be more effective in improving sow lifetime production