Publication recommended : -R. Vakili* and A. A. Rashidi.The effects of dietary fat, vitamin E and zinc supplementation on fatty acid composition and oxidative stability of muscle thigh in broilers under heat stress.African Journal of Agricultural Research Vol. 6(12), pp. 2800-2806, 18 June, 2011 -R. Vakili*, R. Daliri, 2010.The effect of different levels of vitamin e on humoralimmunity, and performance in broiler chicks.Journal of Veterinary Research. 2010, 65(3), pp. 239–244. https://www.sid.ir/En/Journal/ViewPaper.aspx?ID=259982 -R. vakili, A.A. Rashidi and S.sobhanirad.2010. Effects of dietary fat, Vitamin and zinc supplemention on tibia breaking strength in female broilers under heat stress.Afican journal of Agricultural Research.Vol. 5(23), pp. 3151-3156, 4 December, 2010. -A.A. Rashidi, y. Gofrani Ivari, A. Khatibyoo and R. Vakili.2010.Effects of dietary fat, Vitamin and zink on Immune Respanse and Blood Parameters of Broiler Reared under Heat stress. Medwell Journals Research journal of poultry Sciensce. 3(2):32-38 Reza Vakili.2021. Impact of different oil sources on mitigating negative effects of heat stress on performance, thigh proximate composition, fatty acids profile, bone status and immunity of broilers. Journal of Animal nutrition and physiology (under review).

1. By Dr. Reza Vakili
Poultry nutritionist
Strategies to improve performance during heat stress
Using good management practices and nutrition

8. WHEN IS CHICKEN “HEAT STRESS”
A GOOD THING ?
QUESTION

9. If you are not ready can happen

10. 1 kg of weight body
264 calenergy (25% for
basal metabolism and 75%
heat to excretion)

11. GENETICS IS FIXED

12. GENETIC POTENTIAL
BIRD
PERFORMANCE
STRESS LEVEL
LOW
HIGH
STRESSORS IN THE ENVIRONMENT MUST BE MINIMIZED

13. Cold
Poor
Ventilation
Humidity
Molting
Poor Litter
Quality
Poor
Sanitation
Heat
Mold &
Mycotoxins
Bacteria
Viruses
Protozoa
Parasites
Loud Noises
Nutritional
Deficiencies
Dirty Water
Crowding
Feed
Restriction
Pecking
Order
Weighing
Rough
Handling
Vaccination
Dust
NH3 / H2S
Beak
Trimming
STRESSORS IN THE CHICKEN HOUSE

14. feed
intake
growth
intestinal
blood flow
fertility
egg shell
quality
hatchabilty
body
temp
water
consumed
peripheral
vasodilation
activity
body posture
change
gular
flutter
panting
egg
weight
chick
quality
egg
production
immune
response
acid-base
changes (pH)
AA digestibility
prostration
death
HEAT
STRESS
Observations : What happens

16. FACT
Young birds are not affected as much
by high temperature as older birds

17. HATCH 4 wks
24o C
(76o F)
32o C
(90o F)
TEMPERATURE COMFORT ZONE
OF POULTRY

18. Normal Body Temperature
41 - 42o C
(106 - 108o F)

19. Body Temperature During
Heat Stress
46o C
(115o F)

20. 46o C
(115o F)
Body Temperature During
Heat Stress

21. HOMEOTHERMS
(Birds)
Heat Sources
Body Temperature
Increase
Environmental
Heat
Metabolic Heat
Production

22. Conduction
Convection
Radiation
Evaporative
Cooling
(panting)
Bird
Heat
Loss

23. FACT
High Environmental Temperature
“Heat Stress”
• “Relative” terms for each animal
• Air velocity and relative humidity are
important factors to consider

24. THE 80-80-80 RULE
80% OF THE TIME
WHEN
THE TEPMPRATURE IS ABOVE 80°F
THE
RELATIVE HUMIDITY IS BELOW 80%

25. Temperature vs Relative Humidity
100
90
80
70
60
50
40
30
12 4 8 12 4 8 12 4 8 12 4 8 12
noon noon
Temperature ( o F )
Humidity ( % )

26. Body Temperature of Birds
Normal Hot Weather
Day
(hot)
Night
(cool)
Body temperature

27. Chronic Hot Weather (Heat Stress)
Day
(hot)
Night
(hot)
Body temperature
Body Temperature of Birds

28. QUESTION
What can be done
in chronic heat stress?
ANSWER
Move the air over the birds
constantly --- produce “wind chill”

29. WINDCHILL
As air temperature rises the windchill
effect produced by air movement
Moving cooler night air is BENEFICIAL

30. WIND CHILL EFFECT
95
90
85
80
75
70
65
50 100 150 200 250 300 350 400 450 500 550
Outside
Air
Temp
o
F
85
80
77
75
74
Air Velocity ( ft/min )

31. FACT
HEAVIER BREEDS OF BIRDS (BROILERS)
ARE NOT ABLE TO COPE WITH HEAT
STRESS AS WELL AS LIGHTER BREEDS
OF BIRDS (LEGHORNS)

32. WHY?
HEAVIER BIRDS HAVE LESS SURFACE AREA FOR
HEAT DISSIPATION PER UNIT OF BODY WEIGHT

33. HEAT STRESS
THERMOREGULATORY
ADJUSTMENTS IN THE BODY
“PHYSIOLOGICAL ADAPTATIONS”

34. FACT
Survival of birds during heat
stress relies more on
physical adaptations rather
than on chemical mechanisms

35. FACT
• Heat production by the bird in an
attempt to stay cool in a hot
environment is greater than heat
production in a cool environment
in order to stay warm

36. …QUESTION…
WHY DO BIRDS DECREASE FEED INTAKE
DURING HIGH TEMPERATURES ?
..ANSWER..
THEY ARE ATTEMPTING TO BALANCE DIETARY
ENERGY INTAKE WITH CALORIE REQUIREMENT
…IMPORTANT CONCEPT TO REMEMBER…
AMINO ACID AND MINERAL REQUIREMENTS REMAIN THE SAME
NO MATTER WHAT TEMPERATURE CONFRONTS THE BIRD

37. …FACT…
PHYSIOLOGICAL ADAPTATIONS
TO HEAT STRESS
ARE NOT FREE
ENERGY IS REQUIRED

38. Thermoregulatory
Adaptations
“Energy Input”
Egg’s
Growth
“Poorer Feed
Conversion”
VERY IMPORTANT CONCEPT
“Maintenance Requirements Increase in Hot Weather”
FACT
Increasing energy intake by only 10 Kcal
is very beneficial in hot weather for Laying Hens

39. THERMOREGULATORY
ADAPTATIONS
TO HEAT STRESS
• Respiratory rate (panting)

40. FACT
Heat stressed poultry dissipate
over 80% of their heat production
by evaporative cooling

41. FACT
IT IS ESSENTIAL FOR BIRDS UNDER HEAT STRESS
TO INCREASE THEIR WATER INTAKE
WATER IS A HEAT SINK

42. PANTING
maintenance
requirement
Energy Demand
O2 consumption
Heart rate

43. EFFECT OF PANTING
CO2 + H2O H2CO3 H+ + HCO3
-
Bloodstream

44. EFFECT OF PANTING
CO2 + H2O H2CO3 H+ + HCO3
-
Lungs
Bloodstream

45. EFFECT OF PANTING
CO2
H+
(pH )
Respiratory
Alkalosis
Bloodstream

46. Relationship of Laying Hen Body Temperature
to pH and pCO2 (Hadi and Sykes, 1982)
35
30
25
20
41oC 42oC 43oC 44oC
(106oF) (108oF) (110oF) (112oF)
7.70
7.65
7.60
7.55
7.50
pH
pCO
2
(mm
Hg)
Body Temperature

47. FACT
Heat stress causes an increase in
K+ excretion in broilers & laying hens
WHY ?

48. HEAT STRESS
CO2
Respiratory
Alkalosis pH = [H+]
Bloodstream

49. KIDNEY TUBULES
Blood
H+ [H+]
K+
K+
K+
To urine

50. Thermoregulatory
Adaptations to Heat Stress
• Respiratory rate (panting)
• Blood flow to various organs change

51. Skin Tongue
Back Larynx
Breast Trachea
Comb Abdominal muscles (400%)
Wattle (respiration)
Heat
Stress
VASODILATION VASO CONSTRICTION
Blood Flow
Changes
Reproductive tract
Digestive tract
Bone (tibia)

52. HEAT STRESS
WHAT CAN BE DONE ?
Management Nutritional
ADJUSTMENTS

53. HEAT STRESS
…FACT…
Most heat stress problems are
related to management
NOT NUTRITION

55. QUESTION
What does this mean?
Do not expect to solve a heat stress problem
by only making nutritional adjustments
-- Implement management changes first --
ANSWER
$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $

56. HEAT STRESS
Management Options
• Clear area around buildings
• Grass cover around buildings
• Flush water lines/cool water
• Paint the roof white
• Paint the water tower white
• Bury water lines underground

57. VERY IMPORTANT CONCEPT
TO REMEMBER
During
Heat Stress
Birds
Maximize
Heat Loss
Minimize
Heat Production

58. QUESTION
How do birds minimize heat
production in hot weather?

59. ANSWER
FEED INTAKE

60. FACT
Increased mortality in poultry
during heat stress is highly
correlated with a digestive
tract filled with feed

61. FACT
As hot weather (heat stress)
approaches, the first noticeable
adverse effect on poultry is a
decrease in feed intake
WHY ?
A PHYSIOLOGICAL ATTEMPT
TO STAY ALIVE

62. Heat Stress
Feed Intake
Energy Consumption
( Nutrient Consumption)
Less metabolic heat production from
digestion, absorption, transport and
metabolism of nutrients in feed

63. QUESTION
Why is there so much interest
in high temperature?
It affects feed intake (ME intake)
(We need the hen to conserve ME)

64. FACT
Rate of lay and egg shell quality will
only be maintained at high
temperatures if energy and nutrient
intake are maintained

65. Nutritional
Adjustments
in
Hot Weather

66. Nutritional
Adjustments
in
Hot Weather
Minimize
Dietary
Protein

70. FACT
Excess protein intake in hot weather is
detrimental due to an increased heat
production in order to excrete nitrogen
from the body

71. Nitrogen Excretion
Protein
Amino Acids
(deamination)
Carbon
Skeletons
NH2
NH3

72. Nitrogen Excretion
NH3
Fish
NH3
(gills)

73. Nitrogen Excretion
NH3
Fish
NH3
(gills)
Birds/Reptiles
Uric
Acid
Mammals
Urea

74. Energy Cost of Nitrogen Excretion
NH3 Urea
Uric
Acid
Very little NH2–C–NH2
2 ATP/mole N
Urea
=
o
=
o
C
C
C
C
–
=
N
N
N
N
C=o
3.75 ATP/mole N

75. Nutritional
Adjustments
in
Hot Weather
Minimize
Dietary
Protein
Replace
CHO calories
with
Fat calories

76. FACT
Dietary use of fat will improve poultry
performance in hot weather.
…However…
The response to dietary fat requires
adequate amino acid intake.

77. How does dietary fat
improve bird
performance
in hot weather?
QUESTION

78. DIETARY FAT
FAT HAS 2.25 X MORE ENERGY THAN CHO AND CP
FAT FREES SPACE IN THE FORMULA
ALLOWING FOR AN INCREASE IN NUTRIENT DENSITY
FAT HAS LESS HEAT INCREMENT THAN CHO AND CP
(THEREFORE, LESS HEAT PRODUCTION IN HOT WEATHER)
FAT SLOWS DOWN RATE OF FEED PASSAGE IN DIGESTIVE TRACT
(MORE EFFICIENT DIGESTION)
FAT IMPROVES PALATABILITY

79. Nutritional
Adjustments
in
Hot Weather
Minimize
Dietary
Protein
Replace
CHO calories
with
Fat calories
Use Fat to
energy in diet
& adjust nutrient
density

80. Nutritional
Adjustments
in
Hot Weather
Minimize
Dietary
Protein
Replace
CHO calories
with
Fat calories
Use Fat to
energy in diet
& adjust nutrient
density
Feed a
well-balanced
amino acid
level
…FACT…
Body temperature INCREASES
in birds during a lysine deficiency

81. Beneficial
Heat Stress
Dietary Changes
Decrease
Heat Increment
“less waste heat”
USE FAT
CALORIES
IMPROVE
AMINO ACID
BALANCE

82. HOT WEATHER
NUTRITIONAL RECOMMENDATIONS
FEED A WELL BALANCED DIETARY AMINO ACID LEVEL
USE DIGESTIBLE AMINO ACIDS
AND
IDEAL PROTEIN CONCEPT

83. Nutritional
Adjustments
in
Hot Weather
Minimize
Dietary
Protein
Replace
CHO calories
with
Fat calories
Use Fat to
energy in diet
& adjust nutrient
density
Feed a
well-balanced
amino acid
level
Use separate
vitamin, TM
packages
“STRESS PACKAGE”

84. Nutritional
Adjustments
in
Hot Weather
Minimize
Dietary
Protein
Replace
CHO calories
with
Fat calories
Use Fat to
energy in diet
& adjust nutrient
density
Feed a
well-balanced
amino acid
level
Use separate
vitamin, TM
packages
Use
growth
promoters

85. Nutritional
Adjustments
in
Hot Weather
Minimize
Dietary
Protein
Replace
CHO calories
with
Fat calories
Use Fat to
energy in diet
& adjust nutrient
density
Feed a
well-balanced
amino acid
level
Use separate
vitamin, TM
packages
Use
Growth
promoters
Fasting
Programs

86. FASTING PROGRAM
“reduces mortality”
9
9 3
6
12
35o C
(95o F)
Raise feeders
(no feed available)

87. HEAT STRESS
“ITS YOUR DECISION”
DO YOU WANT
GROWTH OR SURVIVAL?

88. Growth and survival
• -Supplementation with α-tocopherol has proven to be an effective measure to prevent lipid oxidation (Lin et al., 1989;
Ahn et al.,1995; Cortinas et al., 2001) and to improve sensory quality (O’Neill et al., 1998, Bou et al., 2001) of
poultry meat. Because α-tocopherol protects PUFA from lipid oxidation, its inclusion in the birds’ diet may result in a
higher deposition of PUFA in poultry tissues.
• -There is also evidence suggesting that supplemental Zinc can alleviate negative effects of HS in broiler chickens.
For example, plasma zinc was greatly reduced and hepatic zinc was found to be more than four times the amount lost
from plasma (Klasing, 1984). Supplemental zinc is used in poultry diets and is reported to be of benefit to laying hens
during environmental stress (Sahin and Kucuk, 2003).
• -zinc may improve shell quality by assisting the activity of the carbonic anhydrase enzyme, as zinc is a key mineral
element of this critical enzyme.
• - Interactions among minerals and other nutrients e.g., vitamin E are extensive and may be important in the
determination of biological availability of other nutrients. Lipid oxidation causes loss of nutritional and sensory
values, as well as the formation of potentially toxic compounds that compromise meat quality and reduce its shelflife.
One of such product is malondialdehyde (MDA), which has long been considered as an index of oxidative rancidity.
Among all the methods proposed for assessing MDA, the 2-thiobarbituric acid (TBA) has been widely adopted as a
sensitive assay method for lipid oxidation in animal tissues.

89. African Journal of Agricultural Research Vol. 6(12), pp. 2800-2806, 18 June,
2011
Available online at http://www.academicjournals.org/AJAR
ISSN 1991-637X ©2011 Academic Journals
• The effects of dietary fat, vitamin E and zinc supplementation on fatty acid composition and
oxidative stability of muscle thigh in broilers under heat stress
• R. Vakili* and A. A. Rashidi
• Department of animal science, Islamic Azad University- Kashmar Branch, Kashmar, Iran.
• Accepted 30th May, 2011
• The objective of this experiment was to characterize the relationship between dietary fat and antioxidant supplementation on performance, fatty acids profile and lipid
oxidation of thigh meat stored under refrigeration in broilers under heat stress. The chicks with a similar body weight were equally assigned to one of the two
controlled-environment chambers from 21 to 56 day of age. The birds feddiets as: 1) basal diet supplemented with 5% saturated fatty acid, 2) basal diet supplemented
with 5%unsaturated fatty acids (2% canola oil plus 3% fish oil); and 3) The second diet supplemented withantioxidant (100 IU vitamin E and 50 mg/kg zinc); that birds
received this 3 diet in two temperature (22and 32°C).Results showed that feed conversion ratio was not influenced by fat type, but on live body weight and feed Intake
had significant effect (P<0.05). High environmental temperature showed deleterious effects including: reduction of feed intake, and live body weight and increasing of
feed conversion ratio. Proportion of omega-6 to omega-3 (n-6/n-3) of thigh was increased and
• polyunsaturated fatty acids (PUFA) decreased in heat exposed and tallow-fed chicks. Whereas the proportion of omega-6 to omega-3 (n-6/n-3) of thigh was decreased
and polyunsaturated fatty acids (PUFA) increased in chicks fed with canola and fish oils. Fat content and gross energy of thigh in heat exposed and canola and fish oils
with antioxidant fed chicks were higher than other treatments.Proportion of omega-6 to omega-3 (n-6/n-3) of thigh was decreased and polyunsaturated fatty acids
(PUFA) increased in chicks fed with canola and fish oils. Inclusion of canola and fish oils supplementations increased lipid oxidation of thigh muscle based on TBARA
values. Thiobarbituric acid reaction substances (TBARA) values of thigh muscle in chicks fed canola and fish oils reared under heat stress was higher than other
treatments. Increasing dietary antioxidants decreased TBARA
• values of thigh muscle.
• Kay words: Broilers, heat stress, dietary fat, fatty acids profile, thigh.
• Other publication recommended :
• R. vakili, A.A. Rashidi and S.sobhanirad.2010. Effects of dietary fat, Vitamin and zinc supplemention on tibia breaking strength in female broilers under heat stress.Afican journal of Agricultural
Research.Vol. 5(23), pp. 3151-3156, 4 December, 2010.
• A.A. Rashidi, y. Gofrani Ivari, A. Khatibyoo and R. Vakili.2010.Effects of dietary fat, Vitamin and zink on Immune Respanse and Blood Parameters of Broiler Reared under Heat stress. Medwell
Journals Research journal of poultry Sciensce. 3(2):32-38
• Reza Vakili.2021. Impact of different oil sources on mitigating negative effects of heat stress on performance, thigh proximate composition, fatty acids profile, bone status and immunity of broilers.
Journal of Animal nutrition and physiology (under review).