Play in Fattening Pigs: Prevalence and Potential as Indicator of Positive Welfare.

Play is considered a promising indicator of positive animal welfare. However, especially in older animals, significant knowledge gaps exist regarding its prevalence and influencing factors. Thus, we analyzed play in fattening pigs at the beginning (n = 229) and at the end (n = 146) of fattening. The evaluation considered social (SOC), locomotor (LOC) and object play (occupation with a metal chain (CHAIN) or nibbling toy), the aggregation of SOC+LOC and play in total (Pt). The statistical analysis focused on play event duration, number of play events/(hour*animal) and play duration/(hour*animal), considering effects such as fattening stage, sex and group size. There was 34.7% more (p = 0.0076) and 121.1% longer (p < 0.0001) Pt in the older pigs with further effects of sex and group size. These results were strongly impacted by the predominance of CHAIN, which partly exhibited characteristics of stereotypic behavior. Additional difficulties in object play arose from possible confusion with exploratory behavior. Given further challenges in reliably identifying SOC, we propose focusing on LOC as promising indicator of pig welfare in the future, which also has greatest potential for automatic detection.