Development of test for determining olfactory investigation of complex odours in cattle

The sense of smell is likely to influence the behaviour of domestic and captive animals in a wide range of management and housing situations. In domestic cattle, there may be unexploited potential for using odours and olfaction in the management; however, published studies on bovine olfactory capacity are scarce. By applying an olfactory Habituation/Dishabituation test developed for rodents, this study aimed to assess olfactory ability in cattle. Twenty-three cows (n = 10) and heifers (n = 13) were tested with three different odours (orange juice, liquid coffee and tap water as an odourless control) presented in a test bucket. The test was conducted on individual animals in their home pen and consisted of each odour being presented twice in a row for 2 min each with an inter-trial pause of 2 min. Following another 2-min pause without odour the animal was presented with a new odour, with order of odour presentation balanced among animals. Duration of sniffing (muzzle in proximity or contact with) the test bucket as well as the occurrence of licking or biting the test bucket were recorded by direct observation. All animals sniffed an odour (i.e. the test bucket) less when presented for the second time (habituation; all 1st vs. 2nd presentations: P < 0.001). Sniffing duration increased at the subsequent presentation of a new odour (dishabituation; all 2nd vs. 1 st presentations: P < 0.001). All animals sniffed coffee and orange longer than water (water vs. coffee: P < 0.001 and water vs. orange: P < 0.001), but they also sniffed coffee longer than orange (P = 0.021). Licking or biting behaviour occurred only when presented with coffee or orange (13 out of 23 animals for both samples). The test showed that cows and heifers were able to distinguish between different complex odours (coffee and orange juice), and that the animals showed increased interest for one of the odours (coffee). This is the first example of a Habituation/Dishabituation test being adapted for and applied to cattle. The test may require further development, but represents the first steps towards exploring the possibility of using odours when adapting or enriching the environment in which we keep cattle.