Endocrine adaptations in the foal over the perinatal period

Abstract

SummaryIn adapting to life ex utero, the foal encounters a number of physiological challenges. It has to assume the nutritional, respiratory and excretory functions of the placenta and activate full regulatory control over its own internal environment for the first time. To achieve this, there must be structural and functional changes to a wide range of tissues including several endocrine glands. In most species, including the horse, these maturational changes begin in late gestation and continue into the first few days of neonatal life. Consequently, during this perinatal period, there are major changes in the sensitivity and/or set point of key endocrine axes, which alter the circulating hormone concentrations in the foal. In turn, these endocrine changes are responsible for many of the other physiological adaptations essential for neonatal survival. The perinatal alterations in the hypothalamic-pituitary-adrenal (HPA) axis are particularly important in these processes, although the sympatho-adrenal medullary axis and endocrine pancreas also have key roles in ensuring homeostasis during the multiple novel stimuli experienced at birth. Abnormalities in the perinatal endocrine profile caused by adverse conditions before or after birth may, therefore, lead to maladaptation or aid survival of the newborn foal depending on the specific circumstances. This review examines the perinatal changes in endocrinology in normal and compromised foals and the role of these endocrine changes in the physiological adaptations to extrauterine life with particular emphasis on the HPA axis, adreno-medullary catecholamines and the endocrine pancreas.

Survey on basal blood plasma catecholamine concentrations in Martina Franca donkey (Equus asinus)

“…The concentrations we found in Martina Franca donkeys are similar to those reported in resting horses [5,9,15,16]. Fowden et al [17] studied plasma catecholamine concentration variation in newborn pony foals and found that after birth adrenaline and noradrenaline concentrations are over 3000 ng/L and they decreased within 6-8 h to basal concentrations of 200 ng/L, similar to those observed in donkey in the current paper. We found no differences in catecholamine concentrations between male and female donkeys.…”

“…sports animals), transport and lairage [14] in horses but there are no data on plasma catecholamine concentrations in donkeys. Fowden et al [17] studied plasma catecholamine concentration variation in newborn pony foals and found that after birth adrenaline and noradrenaline concentrations are over 3000 ng/L and they decreased in donkey in the current paper. Fowden et al [17] studied plasma catecholamine concentration variation in newborn pony foals and found that after birth adrenaline and noradrenaline concentrations are over 3000 ng/L and they decreased in donkey in the current paper.…”

Multiple adrenocortical steroid response to administration of exogenous adrenocorticotropic hormone to hospitalized foals

“…Maturation of the equine fetal HPAA in terms of cortisol secretion occurs late in gestation compared to other species . Fetal cortisol concentrations increase rapidly 4‐7 days before delivery when 17α‐hydroxylase expression rises in the zona fasciculata .…”

A racing start in life? The hurdles of equine feto‐placental pathology

“…2003). The influence of inflammatory mediators, cardiovascular/cord compromise, hypoxia and other disease processes are poorly documented in horses, but may have interesting correlations with human perinatal disease and are discussed further in other reviews in this supplement Fowden et al . 2012; (Ousey and Fowden 2012).…”