Pj. Goddard et al., The behavioural, physiological and immunological responses of lambs from two rearing systems and two genotypes to exposure to humans, APPL ANIM B, 66(4), 2000, pp. 305-321
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.