Parámetros genéticos para sobrevivencia al nacer en porcinos (Genetics parameters of survival at birth in pigs)

Direct (h2d) and maternal (h2m) heritabilities, genetic correlation between direct and maternal effects (rdm), heterosis, phenotypic (Tf), genetic (Tg) and environmental (Ta) annual trends, were estimated using 15308 records of litter survival at birth (LSB), with two methodologies: Least Square (LS) and Restricted Maximum Likelihood (REML). The model included year and season of birth, farm, number of calving, litter breed group as fixed effects, number of piglets born alive and litter weight at birth as covariates. In addition, for LS sire, and for REML animal (direct) and dam (maternal) effects were included as random effects. The analyses were separated for white breeds (WB; Large White =LW and Landrace =L) and for color breeds (CB; Duroc = D and Hampshire = H). The adjusted and non-adjusted LSB averages were 94.53 and 93.54% for CB and 93.53 and 95.65% for WB. Estimates of h2d from LS and REML were 0.010, 0.010; 0.004, 0.010; 0.062, 0,020 and non-estimable, 0.010 for LW, L, D, and H, respectively. Estimates of h2m and rdm were 0.010, 0.98; 0.020, 0.95; 0.040, 1.000; and 0.07, 1.000 for LW, L, D, and H, respectively. There was not statistical evidence of heterosis for LSB. The Tg and Ta were 0.580 and 0.684 for LW, -1.11 and 1.230 for L, and were the only different from zero (P