Crated Sow Breeding Values for Mothering Ability reduce Piglet Mortality in Free Farrowing pens

Increased efforts are needed to reduce pre-weaning mortality in free farrowing (FF) systems. One essential aspect is genetic selection for high quality maternal care. Currently, breeding values for mothering ability (EBV_ma, Topigs Norsvin) are based on information derived from sows housed under restrictive conditions. This study aims to validate these breeding values under FF conditions. 56 TN70 sows were assigned, to either Crated (CR, i.e., crated from ± 2 days pre-farrowing to day 5 of lactation, n=28) or Free Farrowing (FF, n=28). EBV_ma (median 0.04%) was categorized as Low (-1.92% to 0.04%, n=28) and High (0.04 to 3.08%, n=27). Data was analyzed using logistic regression with piglet as experimental unit, housing and EBV_ma as fixed effects, and sow as repeated measure. Up to Day 5, total mortality of liveborn piglets was higher in FF compared to CR sows (14.5% vs. 6.2%, P<0.001) and FF sows also had higher piglet mortality due to crushing compared to CR sows (11.8% vs. 1.1%, P<0.001). Overall, Low EBV_ma sows crushed more piglets than High EBV_ma sows (9.8% vs. 3.8%, P<0.001) and both in CR and in FF sows, the odds ratio for crushing was higher in Low vs. High EBV_ma sows, 8.4 (P=0.018) and 2.9 (P=0.004), respectively. There was no significant effect of housing on stillborn piglets. Yet, Low EBV_ma sows had more stillborn piglets than High EBV_ma sows (8.9% vs. 3.9%, P<0.001). Piglet crushing is significantly higher under FF conditions, and is clearly related to EBV_ma. Therefore, genetic variance estimated and utilized under FF conditions will further improve the possibilities for selection of improved maternal care.