Equine sweating and anhidrosis Part 1 – equine sweating

Abstract

Sweating has a variety of functions in mammals including pheromone action, excretion of waste products and maintenance of the skin surface ecosystem. In a small number of mammalian species, which includes humans and the Equidae, it also has an important role in thermoregulation. This review is focused specifically on the thermoregulatory role of sweat in Equidae and the causes of sweating failure (anhidrosis). The first part describes the glandular appearance, sweat composition, and output rates; and considers the latest theories on the glandular control and secretory mechanisms. It is concluded that the glands are not directly innervated but are controlled by the interplay of neural, humoral and paracrine factors. The secretory mechanism is not as simple as previously thought and is mediated by the dynamic interaction of activating pathways, including autocrine control not only of the secretory process but probably also of secretory cell reproduction, growth, and death.

Sweat Gland Progenitors in Development, Homeostasis, and Wound Repair

“…Horses and camels are among the best examples of working animals whose sweating function is critical for their survival and performance; they use apocrine secretion to dissipate heat (Schmidt-Nielsen et al 1957;McEwan Jenkinson et al 2006). Mouse, as the most commonly used laboratory animal, has eccrine sweat glands exclusively present in the pads of their paws, and its trunk skin lacks sweat glands altogether.…”

Body Temperature and Plasma Nitric Oxide Metabolites in Response to Standardized Exercise Test in the Athletic Horse

“…The use of L-NAME also affected splenic contraction and body temperature, therefore contributing to limit physical performance at higher workloads in Thoroughbred horses [17]. Nitric oxide is thus likely to emerge as an important transmitter between the sympathetic nervous system and the local cutaneous blood vessels in the horse [18]. According to our results, the increase in circulating NOx and the moderate correlation with the increase in body temperature after NO promotes skin sudomotor control and increases sweat response to modulate thermoregulation in the exercising horse [19].…”

Plasma Catecholamines, Sweat Electrolytes and Physiological Responses of Exercised Normal, Partial Anhidrotic and Anhidrotic Horses

“…However, previous reports have suggested several possible pathogeneses of anhidrosis including the inability of the sweat gland to respond to adrenaline [3,9] , breakdown of sweat gland secretory apparatus [10] , water channel impairment [11] , atrophy and hyperkeratinization of sweat glands and ducts [3,12] and nutrition deficiencies [12] . In this study, despite the exercise being light to medium light, changes in the heart rate, respiratory rate and rectal temperature in these horses were significant.…”

“…Although the horse body temperature at rest are well-regulated through sweating, in anhidrotic horses there is an absence of sweating, thus the body heat may need to be dissipated by other means particularly evaporation via respiration [2] . This may cause the respiratory rate to increase.…”

“…High environmental ambient temperature and humidity limit evaporative heat loss exposing the horse to the risk of thermal stress [1] . In horses, 80% of body heat is loss through evaporation via sweating mechanisms [2] . In the temperate environment sweating and heat loss through evaporation is efficient [3] .…”