Relationships between infrared temperature and laterality

The aim of this study was to test for associations between infrared temperatures (IRT) of relevant external body surface regions, lateralised behaviours, and milk productivity in dairy cows (N = 31 in a herd of 202 cows). The cows were selected according to their laterality, based on their response (left: N = 15, right: N = 16) in forced lateralisation tests conducted more than a year earlier. Behavioural variables additional to previously determined laterality, and measured daily for 10 days as they returned to pasture after the afternoon milking, included: stopped while walking towards a person in the laneway, standing on the left or right side of the person, speed of walking to the person; and head, ear and tail positions as they passed the person. Then for 6 of the next 7 days, the IRT, waiting time in the loafing area prior to afternoon milking and milk yield variables were measured. IRT measures included maximum and average IRT from replicate daily thermograms of the eyes, ears, muzzle, coronary band of the forelimbs, and the ratio of the eye to coronary band IRTs. Milk yield was determined from the sum of morning and afternoon milking volumes averaged over 6 days. Milk composition, somatic cell count, days in milk and parity were determined by averaging the monthly herd test data either side of the current IRT/ behavioural period. From ANOVA, cows previously determined as right lateralised had higher maximum eye (Both Eyes: Right = 36.5, Left = 36.1, SED =0.16 °C, P = 0.01) and average coronary band (Both Forelimbs: Right = 31.9, Left = 30.8, SED =0.41 °C, P = 0.02) IRT than left lateralised cows. Using multivariate regression, the IRT measure best associated with the behavioural and milk parameters was the ratio of the eye to coronary band maximum IRT (R2 = 92%). The higher the ratio, the more likely the cow was to: be left lateralised, not stop whilst walking, stand on the right rather than left side prior to passing, not pass too slowly or too fast, wait for longer in the loafing yard prior to milking, be of lower parity, have a lower somatic cell count and a higher days in milk. These behavioral and productivity parameters could indicate level of stress or anxiety. Therefore it is concluded that eye and coronary band IRT deserves further investigation as predictors of stress or anxiety in dairy cows.