This document summarizes the effects of cold temperature on various physiological aspects and production parameters in livestock. It defines key terms related to cold stress such as thermoneutral zone and lower critical temperature. It discusses how cold stress can increase feed intake but reduce feed efficiency. Digestibility of nutrients is reduced at temperatures below 20°C, diverting nutrients to heat generation. Production factors like milk yield and reproductive success can be negatively impacted by cold stress if additional feed is not provided to meet energy demands. Health issues in neonatal calves may also be exacerbated in cold environments.

2. Under Supervision of:
Prof. Dr. Gamal Ashour
Professor of animal physiology
PresentedBy :
Ahmed Hassan Amin
M.SC.

3. content
1. Introduction
2. Definations
3. physiological responses
4. Feed Intake
5. Protein Efficiency Ratio
6. Digestibility of Nutrients
7. Production
8. References

4.  Animals use behavioural means to
aid in body temperature regulation
(Hafez, 1969; Cabanac, 1974).
Behavioural responses may,
therefore, provide a useful index of
the extent to which animals are
able to sense changes in heat loss
to the environment.

5. DEFINITIONS
There are a number of terms that need to
be defined prior to examining the
influence of cold stress.
These terms include:

6. Definations
• thermoneutral zone (TMZ),
• the range of environmental
temperatures where normal body
temperature is maintained and
heat production is at the basal
level
• lower critical temperature (LCT)
• the environmental temperature at
which an animal needs to increase
metabolic heat production to
maintain body temperature.
Definations

10. Definations
• There are four primary ways in which
animals can lose heat to the
environment. These are:
• Evaporation. The body heat is
used to evaporate water mainly
from the skin and hair.
• Conduction. This is heat loss
that occurs as result of direct
contact by the animal with items
such as bedding or stall
surfaces.

11. Definations
• Radiation. This is the transfer of
heat through the air from a warm
object.
• Convection. This loss occurs
when air passes over the body.
Exposure to wind increases the
heat lost by this mechanism.
Definations

13. physiological responses
• However, a point of maximum heat production
(summit metabolism) is reached as a consequence
of extreme cold, and continual exposure to even
lower temperatures results in hypothermia and
reduced capacity of the animal to produce metabolic
heat and, if the situation is not reversed, death of
the animal.

14. Effects Of Cold Temperature On Some
Aspects Of physiological responses
Each steer was exposed in an environmental
chamber to temperatures of 20,O and - 20°C in
September and again in December. After 16 h in the
chamber the frequency of biphasic reticular
contractions was recorded using a fluid filled balloon
placed in the reticulum and connected via a pressure
transducer to a physiological recorder

15. Gonyou et al. 1979

17. Feed Intake
• The dry matter intake of the animals in general is
increased during very cold weather. (Graham et al. 1982).
• increased voluntary feed intake in cold stressed animals
which was attributed to the activity of the thyroid gland
(Gale 1973).
• The elevation of thyroid activity resulted in increased
ruminoreticulum motility and higher rate of passage of
digesta (Gonyou et al. 1979).
• Addition of fibrous ingredients in the diet can also reduce
the effects of cold temperatures.

18. Effect Of Temperature On Lamb PerformanceAnd
Protein Efficiency Ratio
Exposure of livestock to thermal stress (effective
temperature above or below the thermal neutral
zone) affects voluntary food intake and increases
maintenance requirements Protein efficiency
ratio (PER) was reduced when temperature and diet
were such that maximum food intake would not meet
demands for maintenance and growth

19. Ames, et al. 1979

20. Ames, et al. 1979

21. Digestibility of Nutrients
Cold
stress
Reducing D.M
Digestibility
1.8% for each
10C
below 20C
Increase
passage
rate
feed
efficiency
increase fecal and
urinary energy
diverting
nutrients to
heat generation

23. Production
• If cows are not fed additional feed does not
allow them to eat enough to meet their
additional energy requirements
• In this condition
• increased neonatal mortality
• reduced growth rate in surviving calves
• cows usually have delayed return to estrus
• poorer reproductive success

24. lower milk production
• Cold exposure may directly limit the synthetic capacity
of the mammary gland by reducing mammary gland
temperature (Johnson 1976), or may act indirectly
affecting the udder’s blood supply

25. Health Of Neonatal Calves Reared In
Warm And Cold Environments

26. Calf Health
electrolyte
Antibiotic
costs
pneumonia
NEVA
cold environments

27. Mean Values For Body Weight, Food
Intake, And Rectal Temperature

28. References
Ames, D. R. and D. Brink (1977). "Effect of temperature on lamb performance and
protein efficiency ratio." Journal of Animal Science 44(1): 136-144.
Fuquay, J. W., et al. (2011). Encyclopedia of Dairy Sciences 2nd Edition, Four-Volume
set, Academic Press.
Sejian, V., et al. (2012). Environmental stress and amelioration in livestock production,
Springer.
Webster, A., et al. (1969). "Cold climate and cold temperature induced changes in the
heat production and thermal insulation of sheep." Canadian journal of physiology and
pharmacology 47(6): 553-562.
Young, B. (1981). "Cold stress as it affects animal production." Journal of Animal
Science 52(1): 154-163.
Webster, A., A. Hicks and F. Hays (1969). "Cold climate and cold temperature induced
changes in the heat production and thermal insulation of sheep." Canadian journal of
physiology and pharmacology 47(6): 553-562.