Abstract. Genetic crossbreeding and advanced management have substantially improved swine productivity, yet reproductive outcomes in commercial herds remain strongly influenced by environmental and genetic factors. This study quantified these effects on key farrowing and lactation traits in multiparous sows under intensive production, identifying genetic lines that sustain high performance under variable conditions. Farrowing year (FY) and parity number (PN) significantly influenced all farrowing traits and most lactation traits (P<0.05). Genetic group (GG) affected total piglets born (TPBs), piglets born alive (PBAs), and total litter birth weight (TLBW) (P<0.05). Sow weight at farrowing (SWF) and gestation length (GL) exerted linear effects on TPBs (βSWF = 0.01996 piglets per kg; βGL = −0.5344 piglets per day) and PBAs (βSWF = 0.01560; βGL = −0.5248). Cross-fostering increased piglet weight at day 21 (LWW21) and number of piglets weaned (NPWs) (P<0.0001). Insemination season (IS) affected stillborn piglets (SPs) (P=0.0152) and average weaning piglet birth weight (AWPW) (P=0.0078), while season farrowing (SF) influenced AWPW and NPWs (P<0.0001 and P=0.0447, respectively). Estimates of heritabilities (h2) were low for most traits (0.00–0.07) but moderate for LWW21 (0.21) and AWPW (0.13). Farrowing year and parity number are dominant non-genetic drivers of prolificacy and litter growth in intensive systems. Integrating optimized reproductive management, cross-fostering protocols, and sow body condition control with targeted genetic selection and enhanced nutrition and climate regulation offers a strategic pathway to maximize reproductive efficiency and farm profitability.
González-Sánchez et al. (Thu,) studied this question.