Environmental enrichment strategies for growing pigs: Effects on welfare indicators and stress-related responses

This study investigated the impact of different environmental enrichment strategies on the welfare of growing pigs under industrial housing conditions. Four groups of piglets (n = 22 heads per group) were housed on fully slatted floors and provided with various enrichment objects: cotton rope, grain-filled plastic bottles and wrapping paper balls, whereas the control group had none. Welfare parameters, including lameness; injuries to the body, ears, carpal joints and tails; and tear staining intensity, which is a biomarker of stress, were assessed weekly via modified Pig Welfare Quality Assessment protocols. Statistical analyses were performed via the Wilcoxon signed-rank test and the Friedman rank variance test. The absence of enrichment resulted in a significant increase in the incidence of lameness, carpal joint lesions and body-side injuries (P < 0.05). Compared with the enriched piglets, the control piglets also presented markedly greater rates of ear and tail biting. Among the enrichment types, grain-filled bottles provided the most stable welfare outcomes, maintaining low levels of both physical injuries and tear staining intensity. In contrast, pigs exposed to transient or less interactive enrichment presented higher emotional stress indicators. Overall, the results confirmed that the type and functionality of enriched objects play a decisive role in mitigating harmful oral manipulations, improving locomotor health and reducing chronic stress. Tear staining intensity has proven to be a reliable noninvasive parameter of welfare and is sensitive to changes in environmental conditions. Implementing diversified enrichment strategies alongside regular welfare monitoring can serve as an effective tool for increasing pig welfare and production efficiency in intensive farming systems.