468 Maternal resilience to gestational social stress impacts growth and behavior of suckling pigs

Abstract Social stress during gestation has been demonstrated to influence piglet health, growth, and behavior. This study aimed to classify pigs exhibiting resilience or vulnerability to gestational social stress using salivary cortisol and characterize differences in their piglets during lactation. At 30 d of gestation, 40 gilts and first parity purebred Yorkshire pigs were socially mixed in group pens (n = 8/pen). Saliva was collected at 1200 h each day at -1, 0, +1, +2, +3, +7d relative to social mixing. Salivary cortisol pattern was used to identify 6 females whose salivary cortisol concentrations returned to baseline as stress resilient (SR) and 6 females whose salivary cortisol concentrations remained increased as stress vulnerable (SV). After farrowing, all piglets of the 12 SR and SV sows had birth weight, weaning weight, and pre-weaning average daily gain (ADG) recorded. At approximately 3 wk of age (18 ± 2d), piglets underwent a novel object test (NOT) by lowering a novel object into each farrowing crate and capturing continuous overhead video recording for 10 min. Videos were manually decoded for each piglet to identify three behavioral measures: latency to touch the object, total time spent interacting with the object, and number of object touches. At 1 d pre-weaning (24 ± 4 d) total skin lesions were recorded for each piglet. All data were analyzed using linear mixed models correcting for sow parity (1 or 2), sex, body weight, age, and litter. Birth weights did not differ between those born to SR or SV sows (SR: 1.3 ± 0.1 kg, SV: 1.3 ± 0.1kg, P = 0.668). However, suckling piglets born to SR sows had significantly greater ADG compared with those born to SV sows (SR: 183 ± 4 g/d, SV: 168 ± 4 g/d, P = 0.010) resulting in significantly greater weaning weights (SR: 5.7 ± 0.1kg, SV: 5.5 ± 0.1kg, P = 6.7e-09). We detected no differences in any of the NOT measures. At the end of lactation, offspring born to SR sows tended to have fewer skin lesions than those born to SV sows (SR: 0.73 ± 0.12, SV: 1.32 ± 0.12, P = 0.065). These results suggest that maternal resilience to gestational social stress is associated with improved suckling pig growth performance and reduced intra-litter aggression.