7 - Behavioral Indicators of Post-weaning Stress Susceptibility in Cross-fostered Pigs

Cross-fostering is a common swine husbandry practice; however, little research has focused on the effects of foster stress on piglets post-weaning. This study evaluated the effect of cross-fostering on behavioral indicators of post-weaning stress susceptibility. Litters (n = 40) were allocated to 1 of 2 treatments: control (CON) and foster. Three piglets (FOS) from each CON litter were randomly selected and moved to a foster litter 12-24 h post-farrowing, where they were nursed along resident (RES) piglets until weaning (approximately 18 d of age). At 21- and 28-d post-weaning, a male and female piglet from each treatment (FOS, RES, CON) underwent 1 of 2 behavior tests: social isolation and social confrontation. Both tests were conducted in an isolated 1.22 × 1.22 m novel pen. For social isolation, escape attempts, movement between floor quadrants (i.e. locomotion), defecation, and urination events were counted. For social confrontation, the latency to first aggressive interaction and the number of aggressive interactions were quantified. All data were analyzed using the GLIMMIX procedure in SAS. The CON piglets moved between quadrants more frequently than RES piglets (P = 0.02), while FOS piglets moved between quadrants intermediate to (but not different from) CON and RES piglets ( P = 0.44 and 0.12, respectively). Females moved between quadrants more frequently than males (P < 0.0001). The latency to first aggressive interaction was shorter in FOS piglets compared to CON piglets (P = 0.048). There was a treatment by sex interaction (P < 0.01) for number of aggressive interactions, with CON and RES females having more aggressive interactions than their male counterparts (P = 0.04 for both) while FOS females had fewer aggressive interactions than FOS males (P = 0.007). No additional differences were detected (all P > 0.05). Overall, these results provide little evidence that FOS piglets exhibit an increase in behavioral stress susceptibility post-weaning. However, future work should expand upon and clarify the social confrontation findings.