Endocrine Abstracts

Inappropriate control of the hypothalamo–pituitary–adrenal (HPA) axis in production animals has serious consequences for animal welfare, and economic consequences in relation to food production. Fertility rates have declined as a consequence of farming practice and selective breeding, which may result in an increased susceptibility to disease and infection. Whilst precise monitoring of HPA status can be achieved through measurement of plasma cortisol levels, obtaining these samples from production animals can be time-consuming and invasive. Our current study was performed to determine the usefulness of salivary cortisol samples from sheep and cows, in assessing HPA activity. Two studies to model stress were employed; in the first, the stress response to shearing was determined in Suffolk x mule ewe lambs (n=10); in the second, the anxiety response following maternal separation in Holstein-Fresian or Angus-Fresian calves (n=8) was determined. In both studies, saliva samples were collected using either a swab or with a modified stomach tube and syringe. All samples were stored in salivettes and kept at −20 °C, prior to centrifugation and assay for salivary cortisol (by ELISA). In the sheep studies, salivary cortisol dramatically increased within 1 h of shearing, compared with time-matched controls, and remained elevated for up to 6 h post-shearing. In the cow studies, salivary cortisol was also dramatically elevated in calves within 1 h of maternal separation; however, despite having a similar basal cortisol value, the stress response in calves allowed a longer period with their mothers prior to separation was only half that of those separated within 24 h of birth. In summary, we have shown that salivary cortisol measurements in sheep and cows are effective at quantifying HPA activity in these models of restraint and psychosocial stress. Such an approach could be used to improve monitoring of husbandry practice in production animals.