Hypothalamic-Pituitary-Adrenal Axis Dysregulation in Working Donkeys in Northern Nigeria: A Cross-Sectional Analysis

Working donkeys are essential draught animals in agricultural and peri-urban transport settings across northern Nigeria, where they are frequently subjected to chronic physical workloads, nutritional deprivation, and inadequate veterinary care. Chronic stress activates the hypothalamic-pituitary-adrenal axis, resulting in sustained cortisol release with downstream consequences for immune function, reproduction, and metabolism. This study characterised hypothalamic-pituitary-adrenal axis function in working donkeys from three northern states representing high usage populations: Sokoto (North West), Jigawa (North West), and Yobe (North East). One hundred and twenty working donkeys from farms and market areas were assessed, alongside 30 non-working donkeys as comparators. A low-dose dexamethasone suppression test was used to assess HPA axis regulatory function, and basal cortisol, ACTH, and dehydroepiandrosterone sulphate were measured by ELISA. Body condition score, skin wound burden, dentition assessment, and conjunctival mucous membrane colour were recorded as welfare indicators. Working donkeys had significantly higher basal cortisol concentrations and an attenuated response to dexamethasone suppression compared with non-working animals, suggesting HPA axis dysregulation. ACTH was significantly elevated in working animals from Yobe, where nutritional stress was most severe. Cortisol concentrations correlated inversely with body condition score and positively with wound burden. Female working donkeys showed higher cortisol elevation than males at equivalent workloads. These findings provide first data on adrenocortical function in Nigerian working donkeys and highlight the need for welfare-focused interventions including nutritional supplementation and workload regulation in northern Nigeria. Keywords: donkeys, hypothalamic-pituitary-adrenal, cortisol, working animals, welfare.