Interaction between thermoregulation and osmoregulation in domestic animals

Abstract

-The ability to maintain core temperature as well as volume and composition of body fluids within narrow ranges is a major characteristic of mammals. Yet, the ability to maintain a stable core temperature often relies on physiological responses that perturb the stability of body fluids. A common thermoregulatory mechanism that affects body fluid homeostasis is evaporative cooling, by sweating and/or panting, to dissipate heat from the body when core temperature is elevated. However, these responses result in a reduction of total body water, thereby reducing blood volume and increasing the osmotic pressure of body fluids. While both panting and sweating are highly effective means of preventing core body temperature from increasing, unless the resultant body fluid losses are replaced (by intake of water), hypertonicity, hypovolemia, and circulatory collapse can ensue. Thus, physiological control mechanisms have evolved to limit thermoregulatory body fluid losses once they have become a liability and panting and sweating are inhibited. Thus, mammals will tolerate a higher core temperature to minimize further loss of body water. Osmoreceptors located within the lamina terminalis of the brain suppress panting and sweating when the effective osmotic pressure (tonicity) increases. Selective brain cooling (SBC) has been observed in several domesticated mammals when blood flowing to the brain in the carotid rete is cooled. Such SBC promotes reduced panting and sweating, thereby preserving body water. It is also notable that the behavioural response of drinking water can rapidly invoke panting and sweating that override osmoregulatory inhibitory influences on these responses. The preoptic region of the brain has an important role in osmoregulatory and thermoregulatory mechanisms.

Influence of water salinity on the adaptability of confined sheep in the Brazilian semiarid region

“…Physiological control mechanisms in animals have evolved to limit the losses of body fluids, and the elevation of respiratory rate (Table 2) for a longer period may reduce the total amount of body water. Mammals have osmoreceptors in the brain, which suppress heavy breathing and sweating when the effective osmotic pressure (tonicity) increases, preserving body water (McKINLEY et al, 2017).…”

“…When the physiological mechanisms of the animals fail to eliminate excess body heat, their rectal temperature may increase (MARAI et al, 2007;FURTADO et al, 2017), reflecting the elevation in their internal body temperature, resulting in increased respiratory rate and sweating. These are efficient means to dissipate body heat, but may result in a reduction in the amount of body water, reducing blood volume and increasing the osmotic pressure of body fluids (McKINLEY et al, 2017).…”

Estimation of Rectal Temperature of Goats Based on Surface Temperature

“…When subjected to environments with air temperatures above the thermoneutral zone, homeothermic animals employ several thermoregulatory mechanisms to compensate for heat gain, per equivalent loss, and maintain internal body temperature within narrow limits of variation and achieve thermal equilibrium (McKinley et al, 2017). The present study shows that PT, HT, ST, HQ and IR Max increased (P < 0.05) according to the elevation of the air temperature, suggesting that this fact is due to the signi cant increase (P < 0.05) in the body core representative temperature (RT) as a function of the heat generation due to the metabolic reactions and the reduction of the thermal gradient between the animal and the environment, which reduces the ability of the animals to dissipate heat in a sensitive way, being this a primary physiological mechanism responsible for the dissipation of body core heat through the bloodstream to the peripheries and subsequently to the environment (Rizzo et al, 2017).…”

The circle of Willis revisited: Forebrain dehydration sensing facilitated by the anterior communicating artery

“…[ 59 ] In addition to dehydration sensing, the forebrain sensory CVO are also implicated in thermoregulation, [ 60,61 ] a function that is tightly connected to hydromineral homeostasis. [ 62,63 ] Information about blood composition arrives to the OVLT and SFO through two perforating arteries, the supraoptical and subfornical branches of the ACoA (Figure 4A), which either arise directly from the ACoA, [ 34,35 ] or from the subcallosal branch of the ACoA. [ 33,64 ] Let us emphasize that the ACoA originally emerged in amniotes, so other vertebrates do not have a homologous artery.…”