Olfactory awareness in lambs assessed through habituation-dishabituation and approach-withdrawal tests

Abstract

Assessing olfaction in lambs presents methodological challenges due to their precocial development and extreme sensitivity to isolation and novelty. Previous research studied lambs’ olfactory reactivity, particularly to odors from conspecifics, their responses to other odor sources remaining underexplored. To begin addressing this gap, we implemented two tests to evaluate olfactory discrimination in lambs using two distinct odors: dog feces odor (DO) and ovine wool odor (OO). First, after validating the procedure on 10 Suffolk ewes with the same odorous stimuli, a habituation-dishabituation (H-D) test run on 6-day-old lambs (Suffolk, n = 26, 14 females) consisted in repeating 4 times one odor for habituation, followed by a single presentation the other, novel odor for dishabituation (presentation order of OO/DO being counterbalanced across animals). The ewes and lambs habituated to both odors, exhibiting a significant decline in sniffing duration; they also dishabituated to novel odors, attesting their clear discrimination between them. Second, an approach-withdrawal test using boxes scented with these same stimuli was run a group of lambs p (Suffolk, age: 24-day, n = 21). In the approach test, lambs spent significantly more time near objects scented with unfamiliar conspecific wool than those scented with canine feces. Both tests confirmed that lambs clearly discriminate both odors. While the habituation-dishabituation test proved effective in assessing odor discrimination, interpretation of the approach test results was more complex under the given experimental conditions.