1. Managing Heat Stress in Dairy Animals
Prof. Dr. Muhammad Abdullah
Department of Livestock Production
University of Veterinary and Animal Sciences Lahore
Cell #

2. Farm Income
Animal Productivity

3. Genetics X Environment
Animal Productivity
Genetics X Environment

4. Environment
Optimum Productivity is
Function of
COW COMFORT

5. COW COMFORT
Physical
Nutritional
Social
Thermal

6. Not a problem of the animal
Thermal Discomfort
Not a problem of the animal
BUT
A problem of the farmer

8. Buffaloes Sitting in sunlight free choice
during hot sunny day

10. Bos taurus vs. Bos Indicus

11. Genetic Control of Heat Stress
“SLICK” is the major thermoregulatory gene found so far in Bos taurus to combat heat
The mechanism of increased heat tolerance is due to convective and conductive heat loss due to slick gene
There is a need to test for Slick gene in Bos indicus

12. Bos indicus Short reflecting Hair coat Body mass vs. Skin surface
No. of sweat glands
Functional sweat glands
Low metabolic rate
Low production
Less feed intake and slow passage rate

13. Bos bubalus bubalis
Title slide

14. Homeothermy Cattle and Buffaloes are homeotherms
Maintain their deep body temperature essentially constant
Make compensating physiological and behavioral adjustments

15. Animal Environment
Few places in the world where natural climate continuously remains optimum for animals.
Components of the surroundings impose serious limitations on the animal’s productivity.

16. Major Climatic Components
Air temperature,
Humidity,
Solar radiation,
Wind velocity and
Precipitation
produce a combined effect on the ‘thermal comfort’ of the animals and their performance.

17. Air Temperature Most important climatic element in thermal comfort
Immediate surroundings influence the heat exchanged
Four modes of heat transfer, viz., conduction, convection, radiation and evaporation.

18. Humidity The water vapor content affects the capacity for heat loss.
The rate of cooling by evaporation from the respiratory tract and the skin depends on the water vapor content of the air (humidity).

19. when the atmospheric temperature equals or exceeds the animal’s body temperature, evaporation is the only available means of heat loss.
From 21C for Bos taurus cattle and 27C for Zebu cattle, humidity exceeding 60 % becomes a problem affecting their production

20. In A well Ventilated Shed
Shed temperature
Animal Body Temperature

21. Heat Gain = Heat Loss Thermoneutral Zone
Temperatures conducive to normal function
The upper critical temperature is the point where the effects of heat stress start to appear
Introduction makes key points regarding thermo neutral conditions and the upper critical temperature

22. Graph from the 1981 NRC publication. Key things to point out:
Thermoneutral zone
- Optimum for health and performance
Upper critical temperature is where heat stress strarts

23. Sources of Heat Environmental Temperature Metabolic Heat
Heat of radiation (direct/Indirect)

24. The Cow’s Furnace

25. Mechanisms of heat exchange
Conduction: Heat moves from warmer to cooler surface through direct contact.
Convection: The layer of air next to the skin is replaced with cooler air.
Radiation: Heat can radiate from a warmer environment to a cooler environment.
Evaporation: Moisture evaporates from the skin (sweating) and lungs (panting).

26. CONDUCTION

27. How do cows exchange heat with the environment?

28. Temperature Humidity Index (THI)
Includes both temperature and humidity in determining the point at which heat stress may occur
A THI > 72 is considered to indicate heat stress in dairy cattle
THI = (Td + Tw)
The temperature humidity is an index of heat stress. It is a calculated value that includes both temperature and humidity
A THI > 72 is considered to indicate the beginning of heat stress in dairy cattle

29. Example of the Interaction of Temperature and Humidity in Determining Heat Stress Potential in Dairy Cattle
A Dairy Heat Stress Chart provided by Diamond V. This company manufactures yeast culture for inclusion in animal feeds. This lists 5 different zones of heat stress based on information from the University of Arizona. A key thing to point out is that the effect of heat stress at a specific temperature varies with relative humidity. As an example, there is no heat stress at a temperature of 83 F and 20% relative humidity. However, the animal is distressed at a temperature of 83 F and 90% relative humidity.

30. All of These = THI of 72 Temperature, o F Humidity, % 84 15 80 30 7750 75 65 72 95
This chart indicates the interaction of temperature and humidity in determining potential heat stress. All of these temperature-humidity interactions all have the same THI of 72.

31. (Heat Gain ≠ Heat Loss) Heat Stress
The point at which a dairy cow (or other animals) cannot dissipate an adequate quantity of heat to maintain body thermal balance or normal body temperature
(Heat Gain ≠ Heat Loss)
Simple definition of heat stress

32. Signs of Heat Stress body temperatures rises > 102.6 ◦F
Panting>80 breaths per minutes
Reduced activity
Increased water intake
Seek shade
Reduced feed intake (>10-15%)
Reduced milk yield (10 to 20% or more)
These are the mechanisms that a cow has to try to adjust to heat stress.
Body temperature of > o F indicates heat stress. Normal temperature for a cow is
Respiration rates > 70.minute are another index of heat stress. Increased respiration is a primary change cows can make to combat heat stress.
Animals tend to be less active during heat stress.
Water intake may increase by 20 to > 50%
Animals seek shade during heat stress
Animals will look for cool area within a housing unit during heat stress
(Larry E. Chase NY )

33. Effect on Dry Matter Intake
Milk production will usually decrease by variable amounts due to heat stress. .Decreases can be 25% or more.
In 2005, many New York dairy herds reported milk production drops of 5 to 15 pounds per cow per day. At current milk prices, a drop of 10 pounds of milk is a decrease in milk income of $1.50 per cow per day. This is a decrease in income of $150 per day for a herd with 100 milking cows.
Milk production decreases due to:
- Lower feed and energy intake
- More of the intake energy being used for maintenance
- Potential decreases in the efficiency of nutrient use
If early lactation cows are affected by heat stress, there can be a potential loss of milk for the complete lactation cycle.
KG/Day
THI 50-55
THI 65-70
THI 75-80

34. Effect on DMI
Feed intake of lactating Jersey. Brown-Swiss and Holstein depressed at 27C while that of Zebu (Brahman) cows did not decline until 38C.
May be short or long-term
Dry matter intake = Feed intake
Animals under heat stress decrease feed intake by variable amounts. Typical, may be 10-20% decrease.
Actual decrease will depend on the severity and duration of the heat stress.
This decrease can be short-term (days) or longer term (weeks).
Recovery can be slow after heat stress ends

35. Changes in the metabolism
Energy requirements for maintenance increase Increased respiration rate -More blood flow to the skin - Less blood flow to body core - May increase by 20-30%
The proportion of the total energy consumed that is used for maintenance increases. This is due to more work by the animal in an attempt to counteract the effects of heat stress. Increased respiration rates and increased blood flow to the skin are a couple of examples. As more of the intake energy is shifted to maintenance functions. Less energy is available for production functions such as growth and milk production.
Maintenance energy required can increase by 20-30% in heat stress conditions

36. Effect on Milk Production
Decreases due to:
More energy for maintenance
Lower dry matter intake
- Can drop 10 to > 25%
Among Bos Taurus breeds, milk yield starts declining at 21C in Holstein Friesians and in Jersey and Brown Swiss at 24 to 27C.
Milk yield of zebu declines above 32-34C.
Milk production will usually decrease by variable amounts due to heat stress. .Decreases can be 25% or more.
In 2005, many New York dairy herds reported milk production drops of 5 to 15 pounds per cow per day. At current milk prices, a drop of 10 pounds of milk is a decrease in milk income of $1.50 per cow per day. This is a decrease in income of $150 per day for a herd with 100 milking cows.
Milk production decreases due to:
- Lower feed and energy intake
- More of the intake energy being used for maintenance
- Potential decreases in the efficiency of nutrient use
If early lactation cows are affected by heat stress, there can be a potential loss of milk for the complete lactation cycle.

37. Effect on Reproduction
Estrus intensity and length decreased
Conception (fertility) rate decreases almost up to 15%
Decreased growth, size and development of ovarian follicle
Increase early embryonic death
May affect fetal growth and calf size
Reproduction usually decreases for a number of reasons during heat stress:
- If an animal is under any stress, reproduction has a lower priority in terms of metabolism
- Less of the intake energy is available (more of the intake energy is being used for maintenance)
The signs listed in the slide are indexes that heat stress may be depressing reproductive performance. The animals are less sexually active (estrus intensity and duration), have a lower conception (breeding rate), less growth of the follicles that grow on the ovary.
Young embryos may die as a result of heat stress (embryonic death)
Prolonged heat stress can lower the weight of the calf at birth.

38. Factors Which Determine Severity Of Heat Stress
Actual temperature and humidity
Length of the heat stress period
Degree of cooling that occurs at night
Ventilation and air flow
Cow factors (size, milk production)
Housing type , ventilation
Breed
Water availability
Hair coat colour and depth
There are many factors that interact to determine the severity of heat stress. These include:
Actual temperature and humidity (higher = more heat stress)
- Length of the heat stress conditions (hours, days, etc.)
-The degree of nigh cooling (if any) that occurs. How much does the temperature drop at night?
- Ventilation and air flow can help to reduce the impact of heat stress
- Cows producing higher levels of milk production will be affected more by heat stress
The quantity of water available can alter the effects of heat stress (limited water availability will make heat stress worse)

39. Heat Stress in Buffalo
Buffaloes exhibit signs of great distress when exposed to direct solar radiation during hot weather
Buffalo bodies absorb a great deal of solar radiation because of their dark skin and sparse coat or hair
In addition buffalo possess a less efficient evaporative cooling system due to their poor sweating ability

40. Approaches to Minimize the Effects of Heat Stress
Two basic approaches a. Housing and facility management
b. Feeding management
Approaches to minimizing the effects of heat stress.
One choice is to alter the ration fed and the feeding management practices.
Another option is to change things in the barn and other places where the cow lives. This could include things like fans to increase ventilation.

41. Sprinklers
Wallowing Pond

42. Housing and Facility Adjustments
Minimize overcrowding
Restrict movement
Minimize time in the holding area
Provide shade to the animals
1. Natural
2. Artificial
a. Portable
b. Permanent
There are a number of facility adjustments that can be made:
Minimize overcrowding - Overcrowding decreases the ability of animals to dissipate heat.
The holding area (the area where cow wait before entering the milking parlor) on many farms is poorly ventilated. It is often also small and overcrowded.
Can air flow be increased with fans? A goal is an air flow of 4-5 miles/hour.
Sprinklers or misters can be place above the cows to wet the skin (but not soak the cow). If air movement is adequate, then the water is evaporated and removes heat from the cow.

44. 4/28/2017

45. SHED
15F

46. Ventilation
Maintain air flow rate 8-10 km/h with fans.
Forced Ventilation

47. Evaporative cooling Sprinklers to wet the cow’s skin?
Wallowing ponds for buffaloes

50. Wallowing Pond

51. OPEN AREA

52. KEEP AIR MOVING

53. FEEDING MANAGEMENT OF DAIRY ANIMALS

54. Flat Rate Concentrate Feeding
Do not starve profit out of a good cow
Do not feed profit to a poor cow

55. Goals of a Successful Feeding Programme
Optimize milk yield
Feed costs represent largest input cost (60-70%)
Feeding high producing cows
– a continues challenge

56. Nutrient Requirements
Maintenance/Health
Growth
Milk Production
Reproduction
Vary with the stage of lactation and gestation
Activity

57. Priority of Nutrients in the Body
HIGHEST PRIORITY
Maintenance
Growth
Lactation
Fetal Growth
Breeding
Body Reserve
LOWEST PRIORITY

58. Feeding Management
Fresh, palatable high quality feed Uniformity of mixed rations
Minimize feed sorting
Shift feeding times to cooler part of the day
Add some additional fat to the ration but not exceed % of total ration dry matter.
There are a number of changes that can be made in feeding management (the way the ration is fed). These include:
Fresh, palatable feed encourages more feed intake by the animal
Uniformity and consistency of the ration daily assists in improving the efficiency of feed use
Sorting gives the animal an opportunity to alter the ration and decrease the efficiency of nutrient use
Providing fresh feed at the cooler times of the day can stimulate feed intake. The feed will also stay fresher when fed at this time.

60. Ration Adjustments cont.
Decrease the rumen degradable proteins
Consider buffers, yeast and added minerals
Mineral recommendations
Potassium: 1.4 to 1.6 % of DM
Sodium: to 0.45 % of DM
Magnesium: 0.35 % of DM
Adding these types of by-product feeds provides energy that can be used by the rumen microorganisms as a source of energy. However, they have low starch levels and do not contribute to a low (acidic) pH rumen environment.
If protein is provide in excess of requirements, it is excreted from the body. To do this requires the use of energy. Using energy to excrete protein decreases he energy available for milk production.
Buffers can assist in maintaining a normal rumen environment.
Yeast can help improve the efficiency of feed digestion in the rumen.
Added minerals (sodium, potassium) that are lost by increased respiration rates

61. Water Intake may increase by 20 to >50% during heat stress
Clean, fresh cool water always available
Adequate watering devices or
space (minimum of 2-3 inche)
Make sure pressure is adequate to refill waterers
Water availability is a key consideration in giving the animal a chance to cool and combat heat stress. Water intake may increase by 50% or more in heat stress situations.
Water available needs to be clean, fresh and have adequate pressure to refill the drinking vessels.
There should be more than 1 watering device for each group of animals to provide opportunities for drinking and to minimize competition between animals.
Linear water space should be a minimum of 2-3 inches per cow.

62. Water trough should always be in the shed?

64. THANK YOU