Genetic and phenotypic time trends of litter size, piglet mortality, and birth weight in pigs

Introduction Litter size in pigs has increased steadily since 1990. Because of unfavorable genetic correlations with piglet mortality, breeding goals should include survival traits next to litter size. Unbalanced programs that neglect this requirement have produced mortality levels, attracting negative public attention. Balanced does not disadvantage, but the general is largely unaware this. Methods We present long-term time trends as realized commercial breeding. The data includes (i) phenotypes size, birth weight, and used routine value estimation; (ii) genomic Best Linear Unbiased Prediction (gBLUP) estimated values thus obtained. Piglet (2001–2022) weight (2009–2022) were related by recording year. Estimated (EBVs) for regressed on those year (2012–2022). Results Average very weakly correlated ( R 2 ≤ 0.06) (0.07 0.26) traits, are (antagonistic) within each However, all analyzed here show favorable simultaneous phenotypic over time: antagonisms neutralized balanced Above annual mean level, farrowing lactation rates increasing every (unfavorable), intercepts slopes decreased from 2001 2022 (favorable). 2009 within-litter variation coefficient proportion low weights (i.e.,< 0.9 kg) a given decreasing time, critical level (below which increases strongly) clearly population dependent changes too. Discussion due policies lead reduced total numbers dead piglets (i.e., per country, year) coinciding certain pig production volume number weaned piglets).