Development of experimental parameters for conditioned place aversion testing in neonatal goat kids

Conditioned place aversion (CPA) is a behavioral assay used to investigate animals’ affective responses. Animals are typically conditioned to differing experiences in different places, whereupon they are expected to avoid the place where they experienced the most negative (or least positive) experience based on their memory of the events. This approach has been used to assess the affective component of pain in farm animals but has not yet been applied to neonatal goat kids. As animals’ preferences for different environments may be affected by several environmental factors, our objectives were to assess 1) whether side (left or right) and color (red, white, yellow, or blue) influenced kids' preferences and 2) whether kids should be acclimated to the CPA test apparatus alone or in pairs based on their exploratory and vocalization responses (used as proxy measures of stress). 96 goat kids (8 ± 4d) were randomly allocated to testing in pairs (n = 24 pairs) or alone (n = 48 kids) for a 15-minute acclimation test in a three-compartment pen (two colored side compartments linked by a middle neutral compartment). Kids spent more time in the blue compartment compared to yellow but showed no statistical difference in time spent in blue compared to white or red compartments. Additionally, kids displayed a preference for the right compartment compared to the left, regardless of compartment/color combination. When tested alone as compared to in pairs, kids vocalized five times more and halved their number of visits to side compartments. We suggest that of the color combinations examined in the current study, blue and white appear to be suitable choices for use in future CPA experiments, but side preference must be accounted for in experimental design. Further, acclimating kids to CPA tests in pairs, rather than alone, is recommended to reduce stress and promote exploration. Further work is needed to confirm whether the side bias found here persists in other testing contexts (e.g., after conditioning), and to clarify the impact of testing conditioned place aversion in individual goat kids.