| Summary: | The objective of this study was to estimate the genetic parameters of litter size and piglet weight from farrowing to weaning in KHAPS Black sows. The genetic parameters investigated were the direct (h<sup>2</sup><sub>d</sub>), maternal (h<sup>2</sup><sub>m</sub>), realized (h<sup>2</sup><sub>r</sub>), and total (h<sup>2</sup><sub>T</sub>) heritability, as well as correlations (r<sub>d</sub>, r<sub>m</sub>, and r<sub>dm</sub>) within and between traits. The analyses were performed using single- and three-trait animal models with and without maternal genetic effects. In the three-trait model with maternal genetic effect, all estimates of h<sup>2</sup><sub>d</sub> and h<sup>2</sup><sub>m</sub> were significantly different from zero except the h<sup>2</sup><sub>d</sub> of mean birth weight. Positive values of r<sub>d</sub> and r<sub>m</sub> between traits were observed as expected in the range of 0.322–1.000. Negative values of r<sub>dm</sub> were found within and between traits and were less associated with mean piglet weight traits than litter size traits. Estimates of h<sup>2</sup><sub>T</sub> were consistently larger than those of h<sup>2</sup><sub>r</sub> in both the single- and three-trait model analyses. In addition, the three-trait model can take into account the association between the traits, so the estimates are more accurate with smaller SEs. In conclusion, maternal genetic effects were not negligible in this study, and thus, a multiple-trait animal model with maternal genetic effects and full pedigree is recommended to assist future pig breeding decisions in this new breed.
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