212 Growth and behavior of Yorkshire gilts exhibiting physiological resilience to weaning stress

Abstract

Abstract Weaning is an acute early-life stressor and therefore, an excellent model for examining lasting impacts of stress resilience. Our objective was to identify gilts exhibiting physiological resilience or vulnerability to weaning stress and characterize long-term impact on growth and behavior. Purebred Yorkshire litters born to multiparous sows from a single farrowing group were used. At weaning (26 ± 1 d of age), blood samples were collected from all gilt piglets of 13 litters (n = 101) at -1 d, 0 d, and +4 d pre- and post-weaning. Serum cortisol concentrations were quantified by the Michigan State University Veterinary Diagnostic Laboratory. For each litter, serum cortisol was used to identify the gilt most capable of returning to baseline concentrations by +4 d as stress resilient (SR, n = 13) and the gilt least capable as stress vulnerable (SV, n = 13). Skin lesions were recorded at -1 d, +1 d, and +4 d at weaning and when gilts were mixed into grow-finish cohorts. Body weights were recorded at birth, 4 wk, 8 wk, and 12 wk and used to calculate average daily gain (ADG) for the farrowing, nursery, and early grow-finish stages. To assess behavior, focal gilts underwent a social dyad test in a novel arena at 7 wk, a handling test at 8 wk, and novel object test at 12 wk. We observed no differences in skin lesions at weaning, but at 8 wk SR gilts had significantly more rear lesions -1 d pre-mixing (P = 0.031) and middle lesions 4 d post-mixing (P = 0.049). No differences in body weight or ADG were observed at any stage. We did not observe differences between SR and SV pigs during the social dyad or handling tests. During the novel object test, SR gilts exhibited a tendency towards increased activity as demonstrated by a greater number of total zone crosses, 1 m line crosses, and 0.5 m line crosses (P = 0.062, 0.091, and 0.103, respectively). In conclusion, we found gilts resilient to weaning stress were involved in more agonistic behavior at mixing and exhibited increased activity levels in a novel situation. The absence of growth differences supports the potential to select for resilience without negatively impacting growth performance, and the observed behavioral differences could suggest implications for ease of handling and adaptability if females are retained for breeding.