Characterizing the alternative feedback mechanisms in the hypothalamic-pituitary-adrenal (HPA) axis and determining a stressed state in the African wild dog (Lycaon pictus).

Abstract

Glucocorticoids are regulated by the hypothalamic-pituitary-adrenal (HPA) axis and are important in responding to various psychological and physiological stressors. For the African wild dog (Lycaon pictus) only one aspect of the HPA axis has been investigated with no information present on cortisol insufficiency. Here, a pilot study involving both HPA feedback mechanisms is characterized by dynamic function tests (i.e., stimulation and suppression) and a cutoff value for a stressed state is established. Results showed a mean plasma cortisol increase of 40.7% after the administration of Synacthen from initial values, with females recording higher concentrations than males. Using Youden's index, this adaptive response was able to determine a cutoff value of 80.72 ng/ml that infers a stress state. The observed response in the suppression test was similar to that reported in domestic dogs. These results expand the basic knowledge of adrenal function in this endangered species and provide a means in which to determine whether animals are stressed or not. The method used also has application to other species in gauging the degree of stress they are experiencing, which can assist in improving welfare outcomes for captive animals.