Behavioural and physiological effects in sheep of a chronic stressor and a parasite challenge

Abstract

Mature Merino ewes, either at pasture (paddock) or in a feedlot situation (penned), were given a serial challenge infection with the gastric nematode parasite, Haemonchus contortus, and compared with control animals for their behaviour in an arena test, their plasma cortisol concentration and haematological and immunological status. Very low levels of infection resulted and parasitic disease was not evident. There were, however, significant effects on behaviour of both the challenge infection and the feedlot situation. The parasitic treatment resulted in a reduced distance between the sheep and the person in the arena test and also an increase in locomotor activity in the case of penned sheep. Overall, the penned animals displayed twice as much locomotor activity as paddock sheep. Mechanisms whereby a infectious challenge could affect sheep behaviour require further investigation.

Physiological responses to water restriction in dry and lactating Awassi ewes

“…This could explain the weight loss observed to various degrees in all the experimental groups since the average ambient temperature recorded was 29.6 8C. Furthermore, the weight loss observed in all animals could be partly attributed to continuous confinement, similar to what had been noticed by Fell et al (1991). On the other hand, rectal temperature means were not different between groups (Table 2).…”

The eosinophil leucocyte, a phenotypic marker of resistance to nematode parasites, is associated with calm behaviour in sheep

“…6,12 The sheep were brought to a yard close to the arena and drafted into their respective groups before the test commenced according to three marks sprayed on with a scourable branding¯uid (Sire Sine Spray Mark; Cheetham Rural, Sydney, Australia). 6,12 The sheep were brought to a yard close to the arena and drafted into their respective groups before the test commenced according to three marks sprayed on with a scourable branding¯uid (Sire Sine Spray Mark; Cheetham Rural, Sydney, Australia).…”

“…Indeed, there is now good evidence that immunological, neural and endocrine functions interact. 6 The arena permits detection of a balance between two con¯icting motivational systems: the sheep's fear of humans (¯ight distance) versus their natural tendency to approach other sheep in the¯ock. 4,5 Immune responses induced by Haemonchus contortus may aect behaviour in sheep when assessed in an arena test.…”

“…2,3 Parasites can modify the behaviour of their hosts, either directly through the parasite burden, or indirectly by in¯uencing the immune system; this is evident in bighorn sheep and feral horses where their behaviour, reproductive success and survival were modi®ed by parasite burden. Fell et al 6 measured the approach distances, travel and moves for sheep receiving a trickle infection of parasites; 6 these sheep did not exhibit parasitic disease, because they developed a strong immunity against the infection, which was indicated by low faecal egg count (FEC). 6 The arena permits detection of a balance between two con¯icting motivational systems: the sheep's fear of humans (¯ight distance) versus their natural tendency to approach other sheep in the¯ock.…”

“…4,5 Immune responses induced by Haemonchus contortus may aect behaviour in sheep when assessed in an arena test. Fell et al 6 concluded that sheep that became immune to internal parasitism exhibited a change in their behaviour when they were exposed to further challenge by the same parasite and that the arena test was a sensitive method which helped to detect changes in the complex behaviour of sheep. Fell et al 6 measured the approach distances, travel and moves for sheep receiving a trickle infection of parasites; 6 these sheep did not exhibit parasitic disease, because they developed a strong immunity against the infection, which was indicated by low faecal egg count (FEC).…”