Lateralised Behavioural Responses in Livestock to Environmental Stressors: Implications for Using Infrared Thermography to Assess Welfare Conditions.

Lateralised behavioural responses to environmental stressors have become more frequently used as indicators of social welfare in animals. These lateralised behavioural responses are under the control of asymmetrical brain functions as part of the primary functions of most vertebrates and assist in primary social and survival functions. Lateralised behavioural responses originating from the left hemisphere are responsible for processing familiar conditions, while the right hemisphere is responsible for responding to novel stimuli in the environment. The forced lateralisation and side preference tests have been used to determine the visual lateralised behavioural responses in livestock to environmental stressors. Limb preference during movement has also been used to determine motor lateralisation. Although behavioural investigations in livestock have recorded lateralised behavioural responses to environmental stressors, there are still limitations in the implication of lateralisation to other conditions, such as restraint and invasive procedures. Thus, it is important to have a non-invasive measure for these lateralised behavioural responses. Recently, lateralised behavioural responses have been correlated with the use of infrared temperature of external body surfaces, such as the eyes and coronary bands of limbs. This review summarised the different forms of the lateralised behavioural responses in livestock, especially cattle and horses, to environmental stressors, and the association between these responses and the relevant external body surfaces' infrared temperature, with the purpose of improving the use of non-invasive measures in assessing welfare conditions in animals. The combination of the lateralised behavioural responses and infrared temperature of external body surfaces to environmental stressors could improve the assessment strategies of welfare conditions and the related additional husbandry interventions that could be applied to improve the welfare of farm animals.