NOTES - WEEK 1 & 2 vets.pdf - NOTES - WEEK 1 & 2 Monday, 28...

LECTURE 1
Learning outcomes:
Explain how heat is lost from animals •
Explain how heat is gained by animals •
Describe the concepts of homeothermy and the thermoneutral zone •
Provide examples of the adverse consequences of exposure of animals
to temperatures above and below the thermoneutral zone
•
Thermoregulation: Physiological and behavioral processes by which the
animal attempts to maintain a stable internal body temperature by
regulating heat gain and heat loss
*HEAT =/= TEMPERATURE
*Body temperature depends on the balance between heat input and heat
output
Inputs (heat gain) Outputs (heat loss)
Metabolic heat production (from within the animal,
eg when we exercise our muscles generate heat,
can generate heat from digestion – in ruminants
the bacterial breakdown in their stomach generates
heat)
Evaporation
IR from the sun Convection
IR from solid objects (eg other animals) IR from the animal
Conduction from the in-contact environment Conduction into the
in-contact
environment
4 mechanisms of thermoregulation heat loss; IR, Convection, Conduction
and Evaporation
Convection heat loss
Transfer of heat energy by air currents •
Air in immediate contact with the animals skin is warmed by •
NOTES - WEEK 1 & 2
Monday, 28 February 2022 8:41 PM

Air in immediate contact with the animals skin is warmed by
conduction, warm air rises from the body
•
Cooler air moves into contact with the body, forming convection
currents
•
*The greater the SA of the skin, the more effective cooling mechanisms are –
including convection
*Animals may have large ears, floppy skin etc, which allows for greater heat
loss to the surrounding air via convection
Evaporation heat loss
Heat is required to transform water from a liquid to a gas, •
Liquid evaporating from the animals surface has a cooling effect, as the
transformational heat is absorbed off of the animal surface
•
*Panting is a cooling mechanism driven by evaporation by moisture from the
airways, movement of the air helps with evaporation (hence why mouth
open)
Radiation heat loss
Emission of heat energy from the surface of the body in the form of
electromagnetic waves in the IR spectrum
•
Animals can emit or absorb radiant heat depending on their
environment
•
*If the animal is hotter than their environment, they will radiate heat into the
environment and vice versa
Conduction heat loss
Requires direct contact •
Transfer of heat between objects of different temperature •
*Hence why pigs wallow in mud/water, helps conduct heat away from the
body
Set point: Regular "core" body temperature
Heat gain/maintenance
Homeotherm: An animal that is able to maintain a relatively stable core
temperature range by internal means, within a wide range of environmental
temperatures. They can regulate internal processes which control heat
production/conservation, ie:
Shivering •
Non-shivering thermogenesis •