Identifying indicators of resilience and personality in sheep (AEC16-003 and 17-015)

During life on a farm, during transport and at slaughter, farm animals are exposed to many short-term environmental situations which can negatively impact their physiological, behavioural, and emotional states resulting in reduced production, poor health and bad welfare. Resilience is the capacity of animals to cope with these challenges and return rapidly to their pre-challenge status. This project utilised sheep which had been previously identified to have high and low immune responses, and performed a range of tests to assess temperament, attention bias, coping style, spatial memory, learning and physiological stress responsiveness to identify key measures related to resilience and personality. Sheep underwent the same series of tests one year later to examine the consistency of these traits over time. \nLineage: Year 1: UNE animal ethics authority AEC16-003\nOne hundred adult ewes were used in this study, belonging to the Sheep CRC Information Nucleus Flock in Armidale, NSW, Australia. The sheep were 4 years old at the beginning of the study and were a mixture of Merino (n=73) and Merino x Border Leicester (or similar) (n=27) breeds. Sheep were raised in the same flock under extensive conditions and were housed at pasture during periods of behavioural testing. The sheep used in this study were selected from a larger population of 340 ewes that had been immune competence phenotyped, based on both their cell-mediated and antibody-mediated immune responses to vaccines. Sheep were then ranked on immune competence and the top 50 (High) and bottom 50 (Low) ranked ewes were selected for the current study. All ewes then underwent 2 phases of testing over a period of 3 weeks; 1) a circuit in which each sheep rapidly underwent consecutive behavioural testing, 2) maze and food competition tests that were conducted individually.\n\nDuring the circuit, all sheep individually underwent the following consecutive procedures, in the listed order, over a period of approximately 14 min: blood sampling for serum cortisol assessment, attention bias testing (Monk et al. 2018, PLoS ONE, 13(1): e0190404), arena testing (Murphy et al. 1994, Proceedings - Australian Society of Animal Production, pp. 247–250), isolation box testing (Bickell et al. 2009, Developmental Psychobiology 51, 429–438), eye temperature measurement using a FLIR ThermaCam T640 infra-red thermography camera, flight speed assessment and a second blood sample. Prior to their allocated circuit testing day, the sheep had ibuttons attached to progesterone-free CIDRs inserted for assessment of internal body temperature during the circuit (Lea et al. 2008, Australian Journal of Experimental Agriculture, 48(7): 741–745). In the following week, all sheep underwent 3 consecutive days of maze testing (Lee et al. 2006, Applied Animal Behaviour Science, 96(1-2): 43-51) to examine spatial learning and memory. Pairs of High and Low immune sheep then underwent food competition test training and finally food competition testing (Lee et al. 2014, Psychoneuroendocrinology, 47: 166-177). \n\nBlood samples were collected via jugular venepuncture for cortisol analysis using a plain (red-top) plastic Vacutainer. The blood samples were centrifuged at 2000 × g for 15 min at 5°C, then the serum was distributed into 2 ml aliquots that were stored at −20 °C until analysis for cortisol concentration. Serum cortisol concentrations were determined using a commercial radioimmunoassay (Cortisol RIA, MP Biomedicals, Solon, Ohio, USA), previously validated for ovine cortisol (Paull et al. 2007). The average intra-assay coefficients of variance (CV) for quality controls containing 34.2, 86.9 and 182.6 nmol/L of cortisol were 12.0, 9.8 and 4.8% respectively. The inter-assay coefficients of variance were 17.5, 8.9 and 11.0% respectively.\n\nYear 2: UNE animal ethics authority AEC17-015\nThe procedures described for year 1 were repeated on 81 of the ewes available one year later, to determine repeatability of the behavioural and physiological measures. An additional attention bias test was conducted the following week for a total of 3 repeats of this test, while 2 additional food competition tests were conducted for a total of 4 repeats.