Two experiments were conducted to determine whether maximum eye temperature, measured using infrared thermography (IRT), could be a non-invasive technique for detecting responses of cattle to handling procedures. Experiment one used six crossbred heifers randomly assigned to two groups in a crossover design and subjected to i) being hit with a plastic tube on the rump and ii) being startled by the sudden waving of a plastic bag. Experiment two used 32 crossbred bulls randomly assigned to three treatments: i) control, restraint only; ii) electric prod, two brief applications of an electric prod or, iii) startled, as in experiment one, accompanied by shouting. Exit speed (m s−1) was recorded on release from the restraint. Maximum eye temperature was recorded continuously pre- and post-treatment. In experiment one, eye temperature dropped rapidly between 20 and 40 s following both treatments and returned to baseline between 60 and 80 s following hitting and between 100 and 120 s following startling. In experiment two, eye temperature dropped between 0 and 20 s, following both treatments, and returned to baseline by 180 s, following startling plus shouting, but did not return to baseline for five minutes following electric prod. Exit speed tended to be faster following the electric prod. In conclusion, IRT detected responses that were due possibly to fear and/or pain associated with the procedures and may therefore be a useful, non-invasive method for assessing aversiveness of handling practices to cattle.

Infra-red thermography (IRT) is a non-invasive tool for measuring eye temperature as an indicator of stress and welfare in animals. Previous studies state that images are taken from 90° but do not specify a reference point or method of standardisation. The aims of the current study were to determine whether the position of the IRT camera has an impact on recorded temperature and which camera position is optimal for indicating stress in a mammal with anterolateral eyes. IRT images were taken from 90° to the nasal plane, eye and sagittal plane on the left side of the horses’ faces (n = 14) at eye level before and after exposure to a novel object. Distance and angle of measurement was standardised using ground markers. Temperature at each point of measurement was compared against heart rate variability. A significant difference was found between recorded temperature at all three of the points of measurement, both before and after the novel object test, suggesting that IRT camera position has an impact on eye temperature results. There was a significant strong positive correlation between eye temperature taken from 90° to the sagittal plane and heart rate variability, but no such correlation was observed from 90° to the nasal plane or eye. This suggests that a 90° angle in relation to the sagittal plane is the optimal position for taking eye temperature measurements using IRT, whereas 90° to the eye is commonly used. This study offers a validated protocol for using IRT to measure stress and welfare in mammals with anterolateral eyes.

Infra-red thermography (IRT) is increasingly being used to estimate physiological stress responses in animals via changes in eye surface temperature. The aim of this study was to determine whether eye temperature of harbour seals (Phoca vitulina) changes in response to routine handling and the potentially painful procedure of flipper-tagging, and if responses to tagging can be mitigated by subcutaneous injection of lidocaine. Orphaned pups (n = 52) at a rehabilitation facility were assigned to one of four treatments: Lidocaine (handled twice, once for injection and once for tagging); Saline (also handled twice); Tag Only (handled once); Sham Tag (handled once). Eye temperature increased more when pups were first handled compared to pups that were not handled and increased further in pups that underwent a second handling. Eye temperature of pups that were tagged without any previous treatment (Tag Only) increased compared to pups that were sham-tagged. Eye temperature also tended to increase after pups were injected with lidocaine but not saline. These results suggest that: (i) handling causes a physiological stress response; (ii) increased eye temperature arising from the second handling suggests the first handling was likely aversive, resulting in sensitisation to further handling; (iii) the rise in eye temperature after tagging, but not sham-tagging, may reflect pain from tagging; and (iv) lidocaine, at the dosage tested, did not appear to reduce the physiological response to tagging. These results show promise for the use of eye temperature to monitor stress responses and for evaluating the potential aversiveness of routine procedures in seals.