The behavioural, physiological and immunological responses of lambs from two rearing systems and two genotypes to exposure to humans

The behavioural, physiological and immunological responses of lambs from tw o rearing systems and two genotypes to exposure to humans was assessed duri ng and immediately after testing in an open-field arena. Ninety-six lambs o f two genotypes (Scottish Blackface: BF and Texel X (Blue-faced Leicester X Scottish Blackface): T) were used. From birth to weaning one of two manage ment regimes was applied: extensive (E), whereby animals were handled as li ttle as possible or semi-intensive (I), in which lambs experienced a greate r level of human exposure. Eight lambs from each of the four treatment grou ps received an antigenic challenge (Mycobacterium a. paratuberculosis) at 9 weeks of age to allow subsequent testing of immunological reactivity. At 1 and 3 weeks after weaning and 1 year later, lambs were tested in groups of four in a 4.5 X 4.5 m indoor arena, marked with gridlines at 0.75 m interv als. Then were a number of occasions where testing revealed significant eff ects of genotype, management or their interaction, but in an approximately equal number of instances no significant effects of either genotype or mana gement were observed. Genotype significantly influenced the number of squar es occupied in the test arena over a 10-min period before the human entered (100.4 vs. 110.5; sed 2.70 for BF and T lambs, respectively, p < 0.001). I n relation to the number of new squares entered, there was a genotype X man agement interaction: BFE lambs entered fewer squares than TE lambs but foll owing semi-intensive management (I) BF lambs entered more squares than T la mbs (p < 0.05). When a human entered the arena after this 10-min period, wh ile there was a gradual reduction in the number of animals which had not mo ved over the next 5 min, 66 animals had not moved within the allocated time . Also during this period, BF lambs stood facing the human for significantl y longer than T lambs (p < 0.05). At the time of arena testing, 12 lambs fr om each treatment group were fitted with heart-rate monitoring equipment. T here were significant differences in heart rate in relation to period of te sting, i.e, before (107.9) or after (112.3) the point at which the human en tered the arena or when the lambs were walking in the presence of a moving human (126.3 b.p.m.; sed 2.15. p < 0.001). When lambs were alone in the tes t arena, BF lambs had higher heart rates than T lambs(p < 0.05). The heart rate of E lambs increased more than that of I lambs when the human entered the pen (9.4 vs. 0.3 b.p.m.; sed 3.95, respectively; p = 0.05). immediately following completion of the behavioural tests, blood samples were collecte d from subsets of lambs. plasma cortisol concentrations of BF lambs were gr eater than those of T lambs (82.0 vs. 53.5 nmol/l; sed 10.18, p < 0.01) but there was no effect of management. Blood samples collected from the lambs challenged with a novel antigen prior to weaning showed a genotype but not a management effect on both antibody and cell mediated immune responses, al though there was a genotype X management interaction. However, it should al so be noted that there were no significant effects of either genotype or ma nagement on a number of the indices recorded: latency of lambs to move from the initial entry position in the absence or subsequent presence of a huma n: length of time one individual was separated from the other three; distan ce moved in a raceway before stopping; plasma P-endorphin concentrations; h eart rate in the presence of a human. Overall, these results suggest that a lthough differences in responsiveness associated with specific genotypes of sheep can be detected in a test situation, the early life management regim e may also have an effect. The results of this study caution against drawing conclusions between studi es where different genotypes are employed. (C) 2000 Elsevier Science B.V. A ll rights reserved.