Watching makes it worse: Dairy calves are averse to watching another calf feed while hungry

Farm animals are routinely feed restricted, and while this has adverse effects on their physiology and increases their expression of hunger-related behaviours, the subjective experience of hunger remains poorly understood. For example, dairy calves, Bos taurus, are typically fed less than 50% of their ad libitum milk intake. Moreover, farm animals frequently witness conspecifics feeding while hungry, thereby raising the possibility of perceived inequities and associated inequity aversion. Using a conditioned place avoidance paradigm, we explored whether dairy calves display a learnt aversion to a room where they were feed restricted compared to a room where they were fed, feed restricted with cues of another calf feeding (inequity) compared to a room where they were fed, and feed restricted with cues of another calf feeding (inequity) compared to a room where they were satiated following a meal. Calves were not averse to feed restriction alone, but demonstrated aversion to feed restriction in the presence of another calf feeding when this was compared to feeding. Aversion was not maintained when feed restriction with cues of a feeding calf were contrasted with satiation. This study is the first to suggest that dairy calves experience negative affect when hungry and in the presence of a feeding conspecific. However, unlike meal consumption, being satiated was not a positive contrast to feed restriction in the presence of a feeding calf. Although calves displayed more hunger-related behaviours when feed restricted, this did not correlate with place aversion, suggesting that spontaneous behaviours provide limited information on affective state. Given the prevalence of feed restriction in farm animals, our findings have widespread animal welfare implications and open an underexplored avenue to understand the affective experience of hunger in feed restricted farm animals.