Data from Thai Landrace sows were used to estimate genetic parameters for reproduction and production traits in first and later parities. The reproduction traits investigated were total number of piglets born per litter (TB), number of stillborn piglets (SB), and number of piglets born alive but dead within 24 h (BAD). The reproduction data pertained to 12,603 litters born between 1993 and 2005. The production measures were ADG and backfat thickness (BF); these were recorded in 4,163 boars and 15,171 gilts. Analyses were carried out with a multivariate animal model using average information REML procedures. Heritability estimates of reproduction traits for first parity were 0.03 +/- 0.02 for TB, 0.04 +/- 0.02 for SB, and 0.06 +/- 0.02 for BAD. For later parities, they were 0.07 +/- 0.01 for TB, 0.03 +/- 0.04 for SB, and 0.02 +/- 0.01 for BAD. Heritability estimates for production traits were 0.38 +/- 0.02 for ADG and 0.61 +/- 0.02 for BF. Genetic correlations between ADG and TB tended to be favorable, and genetic correlations between BF and TB tended to be unfavorable in all parities. However, BF was genetically correlated unfavorably with SB in later parities, and the genetic correlations between TB and BAD tended to be unfavorable in all parities. The genetic correlations of TB, SB, and BAD between first and later parities were 0.85 +/- 0.13, 0.79 +/- 0.16, and 0.71 +/- 0.24, respectively. Selection for high growth rate will probably increase TB, and selection for low BF will decrease TB and increase SB. The results obtained also indicated that BAD will increase if there is selection pressure for high TB.

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