Modeling feedback-driven behavioral adaptation in pigs under environmental pressure: a study of behavior modification.

Abstract

In commercial pig farming, aggression and stress during herd mixing negatively affect animal welfare and productivity. This study developed an environmental pressure-feedback (EPF) model that applies metabolic and spatial pressure through brief feed withdrawal and crowding animals together in a limited space, combined with resource-based feedback, to modulate pig behavior and stress. EPF treatment significantly reduced fight frequency (95 % CI: -1.95 to -1.28) and skin lesions (P < 0.001), indicating lower aggression. Compared with controls, EPF-treated pigs showed significantly lower cortisol levels at 12 h (-69.80 ng/mL, P = 0.003) and 24 h (-58.15 ng/mL, P = 0.012) post-mixing. Chromogranin A decreased by 2.80 ng/mL (P = 0.035) and 4.34 ng/mL (P = 0.001) at these times. Glucose dropped significantly at 3 h (-2.48 mmol/L, P < 0.001), 24 h (-0.77 mmol/L, P = 0.017), and 7 days (-1.10 mmol/L, P < 0.001). Additionally, EPF-treated pigs had lower body temperature (P < 0.001) and heart rate (P < 0.05) at 3, 12, and 24 h. The reduction in these indicators demonstrates that the EPF model effectively alleviates stress load. This study reveals that the EPF model, by introducing moderate external pressure and utilizing a contrast effect to enhance feedback perception, prioritizes feeding motivation, suppresses aggressive behavior, and attenuates activation of the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, thereby effectively mitigating stress responses.