Genetic Analysis of Production Traits in Different Parities Using Multiple Trait Animal Models in a Thai Landrace-Yorkshire Swine Population

Number of piglets born alive (NBA) and litter birth weight (LTBW) in different parities of 2,124 Landrace (L), 724 Yorkshire (Y), 2,650 Landrace × Yorkshire (LY) and 4,332 Yorkshire × Landrace (YL) sows were analyzed using multiple trait animal models (MTM). All sows farrowed from 1989 to 2013 in a commercial swine population, and all of them had four parities. The MTM contained the fixed effects of farrowing year-season, additive genetic group of the sow, heterosis of the sow, heterosis of the litter and age at first farrowing, and the random effects of sow, boar, and residual. A MTM that considered each trait in each parity as a separate trait (MTM-PAR) was compared with a MTM that considered each trait measured in the first, second and the sum from the third to the last parity (MTM-SPAR) as three separate traits. The estimates of heritability from MTM-PAR ranged from 0.04 ± 0.01 (second parity) to 0.09 ± 0.02 (fourth parity) for NBA, 0.07 ± 0.02 (second parity) to 0.16 ± 0.02 (third parity) for LTBW. Estimates of heritabilities for MTM-SPAR were low for all traits, ranging from 0.04 ± 0.01 (first and second parity) to 0.09 ± 0.02 (third to last parity) for NBA, 0.06 ± 0.02 (second parity) to 0.08 ± 0.02 (third to last parity) for LTBW. Estimates of genetic correlations in MTM-PAR were high for NBA (0.50 ± 0.18 to 0.96 ± 0.02) and LTBW (0.72 ± 0.1 to 0.93 ± 0.07), except between NBA in the first parity with the second (0.29 ± 0.24) and in the fourth parity (0.50 ± 0.18). Estimates of genetic correlations for MTM-SPAR were low to moderate for NBA (0.11 ± 0.19 to 0.54 ± 0.21) and LTBW (0.12 ± 0.17 to 0.23 ± 0.18), but high between LTBW in the first and the second parities (0.83 ± 0.11). Genetic correlations for NBA and LTBW were higher for MTM-PAR than for MTM-SPAR. Results suggested that the MTM that treated each parity as a different trait should be used for genetic evaluation and selection for NBA and LTBW in this swine herd.