heat stress in dairy cattle
DESCRIPTION
Heat Stress in Dairy Cattle. Akrum Hamdy. Introduction. All animals have a zone of thermo neutral temperatures conducive to normal function The upper critical temperature is where the effects of heat stress start to appear. Heat Stress. - PowerPoint PPT PresentationTRANSCRIPT
Heat Stress in Dairy Heat Stress in Dairy CattleCattle
Akrum HamdyAkrum Hamdy
IntroductionIntroduction All animals have a zone of thermo All animals have a zone of thermo
neutral temperatures conducive neutral temperatures conducive to normal functionto normal function
The upper critical temperature is The upper critical temperature is where the effects of heat stress where the effects of heat stress start to appearstart to appear
Heat StressHeat Stress The point at which a dairy cow (or The point at which a dairy cow (or
other animal) cannot dissipate an other animal) cannot dissipate an adequate quantity of heat to adequate quantity of heat to maintain body thermal balance maintain body thermal balance or normal body temperatureor normal body temperature
Source: NRC, 1981
Temperature Humidity Temperature Humidity Index (THI)Index (THI) Includes both temperature and Includes both temperature and
humidity in determining the point humidity in determining the point sat which heat stress may occursat which heat stress may occur
A THI > 72 is considered to A THI > 72 is considered to indicate heat stress in dairy cattleindicate heat stress in dairy cattle
Example of the Interaction of
Temperature and Humidity in Determining Heat Stress
Potential in Dairy Cattle
All of These = THI of All of These = THI of 7272Temperature, Temperature, o o FF Humidity, %Humidity, %
8484 15158080 30307777 50507575 65657272 9595
How Do Cows Respond How Do Cows Respond to Heat Stress?to Heat Stress? Higher body temperaturesHigher body temperatures Increased respiration rates Increased respiration rates
(>70/hour)(>70/hour) Less activityLess activity Increased water intakeIncreased water intake Seek shadeSeek shade Look for cool areas in the barnLook for cool areas in the barn
What Happens What Happens Metabolically?Metabolically? Energy requirements for Energy requirements for
maintenance increase maintenance increase - Increased - Increased
respiration raterespiration rate -More -More blood flow to the skinblood flow to the skin - - Less blood flow to body coreLess blood flow to body core
- May increase by 20-- May increase by 20-30%30%
What About Dry Matter What About Dry Matter Intake?Intake? Dry matter intake decreases in Dry matter intake decreases in
cows subjected to heat stresscows subjected to heat stress- May drop 10-20% - May drop 10-20%
in commercial herdsin commercial herds- Becomes - Becomes
variablevariable - May - May be short or long-termbe short or long-term
How About Milk How About Milk Production?Production? Decreases due to:Decreases due to: - More - More
energy for maintenanceenergy for maintenance - Less - Less energy for productive functionsenergy for productive functions- Lower dry matter intake- Lower dry matter intake - - Alterations in nutrient useAlterations in nutrient use - Can - Can drop 10 to > 25%drop 10 to > 25%
What Happens to What Happens to Reproduction?Reproduction? Usually decreases in heat stress Usually decreases in heat stress
situationssituations Estrus intensity and length decreaseEstrus intensity and length decrease Fertility rate decreasesFertility rate decreases Ovarian follicle growth decreasesOvarian follicle growth decreases Increase early embryonic deathIncrease early embryonic death May affect fetal growthMay affect fetal growth
What Determines the What Determines the Severity of Heat Severity of Heat Stress?Stress? Actual temperature and humidityActual temperature and humidity Length of the heat stress periodLength of the heat stress period Degree of cooling that occurs at nightDegree of cooling that occurs at night Ventilation and air flowVentilation and air flow Cow factors (size, milk production)Cow factors (size, milk production) Water availabilityWater availability Hair coat depthHair coat depth
Which Cow Will Be Which Cow Will Be Affected More by the Affected More by the Sun?Sun?
Heat Stress, Dry matter Heat Stress, Dry matter Intake and Milk Intake and Milk ProductionProduction Used the CNCPS ration model to Used the CNCPS ration model to
predict dry matter intake and milk predict dry matter intake and milk productionproduction
Cow = 1,400 lbs producing 80 lbs. Cow = 1,400 lbs producing 80 lbs. of milkof milk
Varied temperature and humidityVaried temperature and humidity
Conditions for Each Conditions for Each RunRun
RunRun Temp., FTemp., F HumidityHumidity Night Night Temp.Temp.
11 6060 5050 505022 9090 5050 606033 9090 7070 606044 9090 7070 757555 9090 7070 7575
1 lb. of fat was added to the ration in Run 5
Maintenance Energy Maintenance Energy Required – McalRequired – Mcal
02468
101214161820
ME, Mcal
1 2 3 4 5Run
Predicted Dry Matter Predicted Dry Matter Intake, lbs.Intake, lbs.
20
25
30
35
40
45
50
DMI, lbs.
1 2 3 4 5Run
Predicted Milk Predicted Milk Production, lbs.Production, lbs.
0102030405060708090
Milk, lbs.
1 2 3 4 5Run
MEMP
Economic Impact of Economic Impact of Heat StressHeat Stress St-Pierre et. al., 2003St-Pierre et. al., 2003 Estimated costs of heat stress for Estimated costs of heat stress for
both the US and each stateboth the US and each state Included dairy cattle, beef cattle, Included dairy cattle, beef cattle,
swine and poultryswine and poultry Yearly cost = $2.4 billion dollarsYearly cost = $2.4 billion dollars
Total Loss by Animal Total Loss by Animal Type, %Type, %
DairyBeefSwinePoultry
Heat Stress Loss Heat Stress Loss Estimates by State, Estimates by State, Millions of DollarsMillions of Dollars
StateState Loss, Million Loss, Million $$
Dairy, % of Dairy, % of Total LossTotal Loss
New YorkNew York 24.924.9 9898
PennsylvaniPennsylvaniaa
50.850.8 8888
VermontVermont 5.45.4 9898
MarylandMaryland 8.758.75 8686
What Can We Do to What Can We Do to Minimize the Effects of Minimize the Effects of Heat Stress?Heat Stress? 2 basic approaches -2 basic approaches -
a. Adjust the rationa. Adjust the ration
b. b. Adjust the environment inAdjust the environment in
which the cow lives which the cow lives
Ration AdjustmentsRation Adjustments Need to keep the animal healthy!!!Need to keep the animal healthy!!! Select higher quality forages and Select higher quality forages and
more digestible feed ingredients more digestible feed ingredients (lower heat production during (lower heat production during digestion)digestion)
Consider added fatConsider added fat - - Concentrated energy sourceConcentrated energy source - - Low heat of digestionLow heat of digestion
Ration Adjustments - 2Ration Adjustments - 2 Replace some forage with non-Replace some forage with non-
fiber byproduct feeds (beet pulp, fiber byproduct feeds (beet pulp, soy hulls)soy hulls)
Minimize excess total and rumen Minimize excess total and rumen degradable protein (requires degradable protein (requires energy to excrete from the body)energy to excrete from the body)
Consider buffers, yeast and added Consider buffers, yeast and added mineralsminerals
Feeding Management Feeding Management ChangesChanges Fresh, palatable high quality feed Fresh, palatable high quality feed
should always be availableshould always be available Uniformity of mixed and delivered Uniformity of mixed and delivered
rationsrations Minimize feed sortingMinimize feed sorting Shift feeding times to cooler part Shift feeding times to cooler part
of the dayof the day
WaterWater Intake may increase by 20 to >50% Intake may increase by 20 to >50%
during heat stressduring heat stress Clean, fresh water always availableClean, fresh water always available Adequate watering devices or space Adequate watering devices or space
(minimum of 2-3 inches per cow)(minimum of 2-3 inches per cow) Make sure pressure is adequate to Make sure pressure is adequate to
refill waterersrefill waterers
Housing and Facility Housing and Facility AdjustmentsAdjustments Minimize overcrowdingMinimize overcrowding Minimize time in the holding areaMinimize time in the holding area Is shade available?Is shade available? Can air flow be increased with Can air flow be increased with
fans?fans? Can misters or sprinklers be Can misters or sprinklers be
installed to wet the cow’s skin?installed to wet the cow’s skin?
What Heat Stress?
THI Thresholds for THI Thresholds for Other SpeciesOther Species Beef cattle Beef cattle = 72 – 75 = 72 – 75 o o FF
SwineSwine = 72 – 74 = 72 – 74 oo F F
PoultryPoultry = 70 – 78 = 70 – 78 oo F F
SummarySummary Heat stress can decrease animal Heat stress can decrease animal
production, reproduction and production, reproduction and profitabilityprofitability
Ration, feeding management and Ration, feeding management and housing alterations can be made housing alterations can be made to lower the effect of heat stressto lower the effect of heat stress
Summary - 2Summary - 2 The challenge is to balance The challenge is to balance
investment cost versus projected investment cost versus projected returnsreturns
In the Northeast, we have a low In the Northeast, we have a low number of heat stress daysnumber of heat stress days
New facilities being built are New facilities being built are incorporating housing components incorporating housing components to minimize the effect of heat stressto minimize the effect of heat stress
What Heat Stress?What Heat Stress?
Monsanto