Analysis of heat stress in dairy cattle
Adnan Al-KanaanDepartment of Animal BreedingOrganic Agriculture-WitzenhausenKassel University
30-10-2012
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• Heat stress : The magnitude of the force external to the body which tend to displace its system from their resting or ground state • Thermoneutral zone( TNZ) is the range of ambient temperature within which metabolic rate is at a minimum, and within which
temperature regulation is achieved by non-evaporative physical processes alone (Yousef, 1985)• .
Background2
Temperature-humidity index (THI): index developed to assess discomfort related to high ambient temperature and relative humidity
Background3
DANGER
Temperature-humidity index (THI)
1-Dry blub temperature2-Wet bulb temperature3-Relative Humidity4-Dew point Temperature
THI > 72
THI > 68
Physiological traits:1. Rectal body temperature (thermometer)2. Respiration rate( account flank movements)3. Pulse rate ( cow tail)4. Surface body temperature (infrared thermo graphic camera)• Total upper cow body area• Shoulders and back area• Line from back to shoulders • Withers area
Temperature Humidity Index (THI)THI = (1.8 × Tdb + 32) - (0.55- 0.0055 x RH) x (1.8 × Tdb - 26) (NRC, 1971)
Production traits: Milk yield (test-day), protein (%), milk fat (%), milk fat (kg), urea, somatic cell score SCS, days in milk (lactation stage)
Reproduction traits: Days open, conception rate, age at first conception & calving, dry period, calving interval and Dystocia
Health status traits: Mastitis, acidosis, ketosis, laminas and abortion Non-genetic factors: Parity, age, year, season, lactation stage, production system, farm, cattle breed
Data
Ambient temperature C◦, relative humidity % and dew point temperature measured by digital meteorological logger instilling in the cows barns
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The study began in March-2012 in three farms located in Frankenhausen, Malsfeld and Thüringen
Variable N Mean Std Dev Sum Minimum MaximumBody Temperature 1176 38.29218 0.45639 45032 36.30 40.50
Pulse rate 727 76.88721 8.35859 55897 57.00 102.00
Respiration rate 763 30.45675 9.41944 23239 15.00 72.00
upper cow body 347 28.26548 4.25562 9808 14.03 37.53
shoulders and back area 347 27.89205 4.41785 9679 13.74 37.18
line (shoulders to back) 347 27.84078 4.47136 9661 12.27 36.83
withers area 347 27.88009 4.46392 9674 12.75 36.33
15 17.5 20 22.5 25 27.5 30 32.5 35 37.5
0
5
10
15
20
25
Perc
ent
upper 13.75 16.25 18.75 21.25 23.75 26.25 28.75 31.25 33.75 36.25
0
5
10
15
20
25
Perc
ent
shoulders
13.75 16.25 18.75 21.25 23.75 26.25 28.75 31.25 33.75 36.25
0
5
10
15
20
25
Per
cent
withers
12.5 15 17.5 20 22.5 25 27.5 30 32.5 35 37.5
0
5
10
15
20
25
Perc
ent
line
Rectal Body temperature
N=1176
Pulse rate
N=727
Respiration rate
N=763Upper cow body
N=347
Shoulders and back
N=347
Line: from tail to neck
N=347
Withers: cycle in withers area
N=347
Results: Means and distributions 5
Results: Correlations 6
• Preparing the data for analysis• Basic data• Physiological data• Production data• Fertility data• Health data
Strategies7
• Weather data - Overview • Weather data (THI) – Physiological traitsProduction traitsReproduction traitsHealth traits• Genetic analysis• Heritability : Rectal body temperaturePulse rateResperation rateSurface body temperature• Genetic correlations: Physiological traits & Production traitsReproduction traitsHealth traits• Variance components