Place conditioning as evaluation of affective valence in piglets

The emotional valence of animals is challenging to assess, despite being a key component of welfare. In this study, we attempted to assess emotional valence through memory in 1- and 3-week-old piglets. It was hypothesized that piglets would spend less time in a pen where they experienced a negative event (castration) and more time in a pen where they experienced a positive event (enrichment). A testing apparatus was designed with three equally sized pens: two outer sections serving as treatment pens containing unique visual and tactile cues and a center section remaining neutral. Piglets received either negative or positive condition in one outer treatment pen and a sham treatment in the opposite. Various methods were tested (age of piglets, number and length of conditioning sessions, passive vs. active conditioning). Contrary to expectations, piglets did not decrease their time in the pen associated with the negative condition or increase their time in the pen associated with the positive condition. However, when exposed to the positive condition, results indicate older piglets developed an aversion towards the sham treatment. This study provides methodological groundwork for the application of place conditioning in piglets and highlights the nuances important for the use of cognitive tests to assess animal welfare.