Abstract:
A pig is any listed animal species in the genus Sus, within the family Suidae of even-toed ungulates. The
domestic pig (Sus scrofa domesticus) (also referred to as swine or hog) is a large, domesticated, eventoed
ungulate that has its ancestry in the wild boar. Domesticated pigs are commonly raised as livestock
by farmers for pork, hams, gammon or bacon), as well as for leather. For the Pig industry, chronic stress
posed by gestation crates and its often negative consequences are a welfare concern, since stressors
can negatively affect animal production as well as the health of pigs.
When confronted with a stressor, an individual displays a stress response consisting of a suite of
physiological and behavioral alterations to cope with the challenge. In pigs, the assessment of
physiological responses to stress, like the related alterations in glucocorticoid (GC) concentrations, has
already been done, but only by using an invasive approach, with the disadvantage of a possible handlinginduced
stress response. So far, no validated non-invasive method for determining stress-related
responses in pigs seems available. Therefore the study aimed to determine validated stress-related
physiological responses in domestic pigs’ saliva and faeces through the performance of an
adrenocorticotropic hormone stimulation test (ACTH challenge test), the effect of circadian rhythm on
faecal GC levels and to investigate the effect of storage on the rate of metabolism of faecal glucocorticoid
metabolites post-defaecation.
An ACTH challenge was performed on four pigs and with two pigs as saline controls, at University of
Pretoria Biomedical Research Centre (UPBRC), South Africa. Faecal GC metabolites (fGCM) were
validated against four enzyme immuno-assays including the 3α,11-oxo-CM, 3β,11β-diol-CM, 11,17-DOA
and cortisol. The 3β,11β-diol-CM method was subsequently selected and used to investigate for salivary
and faecal GCM. The results indicated that acute salivary cortisol levels can increase up to ~600 % above
the pre-injection baseline levels within 40 to 60 minutes post-injection. Faecal glucocorticoid metabolites (FGCM) levels in the 4 ACTH inoculated pigs reached 2-fold peaks of pre-injection levels within 7 to 36
hours following treatment.
Comparatively, the early morning saliva and faecal samples have higher glucocorticoid concentrations
compared with the late afternoon samples. In addition, fGCM in faecal samples were relatively stable for
over 48 hours demonstrating that faecal sample storage may not affect outcomes of non-invasive
hormone monitoring to assess adrenocortical function in pigs. This method provides an empirically sound
basis for a non-invasive monitoring of adrenocortical function in pigs and serves as template for further
studies which may have value for the monitoring of adrenocortical function in populations of pigs in
different housing units and other stressful conditions.
