Crated sow breeding values for mothering ability reduce piglet mortality in free farrowing pens

Selecting sows with a high genetic merit for mothering ability to ensure the survival of liveborn piglets may be a promising strategy to reduce piglet mortality in free farrowing (FF) systems. This genetic merit, reflected in the Estimated Breeding Value for Mothering Ability (EBVma), is currently estimated based on information from sows housed in conventional crated farrowing systems. Therefore, the objective of the present study was to assess the predictive ability of crated sow breeding values for mothering ability on early piglet mortality, litter characteristics, and farrowing performance in an FF environment. This was achieved by comparing the performance of sows during early lactation in FF with those that were temporarily crated (TC) for the first five days of lactation. A total of 56 healthy TN70 sows were assigned to either TC (crated from approximately 2 d pre-farrowing to day 5 of lactation, n = 28) or FF (n = 28). Overall, higher EBVma were associated with reduced liveborn piglet mortality within the first 5 d of lactation (P = 0.04). In FF, liveborn piglet mortality was higher in low EBVma sows (14.8%) compared to high EBVma sows (6.1%) (odds ratios [OR]: 3.4, 95% CI: 1.5-7.4, P = 0.003). Additionally, piglet crushing rates were higher in low EBVma sows (9.8%) versus high EBVma sows (3.3%) (OR: 2.9, 95% CI: 1.3-7.6, P = 0.01). In TC, the association was less pronounced for liveborn piglet mortality (OR: 2.4, 95% CI: 0.8-7.0, P = 0.11) but present for piglet crushing (OR: 8.4, 95% CI: 1.5-∞, P = 0.02). Higher EBVma values were also associated with a reduced probability of stillbirths (P = 0.02). However, no significant association was found between EBVma and farrowing duration in either housing system, nor was there an effect of housing system on farrowing duration (FF: 251 ± 48.5 min, TC: 251 ± 51.3 min, P = 0.96). As anticipated, piglet mortality was higher in FF (14.2%) compared to TC (5.9%), with piglet crushing being the predominant cause of piglet mortality in FF (11.8%), while deaths of nonviable piglets were more common in TC (4.2%). This study demonstrates that EBVma retain their predictive value in FF and suggests a stronger association with piglet survival in this environment. The significant association between higher EBVma and lower piglet mortality, particularly due to reduced piglet crushing, highlights the potential of genetic selection to enhance piglet survival in FF systems through selection for maternal influence on survival.