Heat Stress in Dairy Cattle: Applications and New Frontiers.
byCN Lee, Ph.D. Dept. of Human Nutrition, Food and An.Sci. College of Tropical Agriculture and Human Resources, University of Hawai’i–Manoa.
Impact of Heat Stress on Cattle.
• July 1995 Heat wave in Iowa 3,750 cattle died, $42.8 million direct losses
• July 1999 Heat wave in Nebraska 5,000 cattle died of heat stress $2131.0 million is direct losses June 2009, Heat wave in Kansas, 2,000 hd. of beef cattle died.
Feedlot Cattle
Dairy Cattle July 2006, Heat wave in California
Losses estimated to be >$1 billion.
Disruption in gonadotropins Secretion: LH
Affects thyroid hormones therefore disrupt metabolism, heart rate, cellular repair, etc.
Decrease contractions in intestines, blood flow to gut, decrease digestion, etc.
Decrease feed intake
Damages follicular development and growth; adverse effect on Oocytes; can take over 60 days for recovery.
Affects placenta steroids, size and lowers birth weights, early birth
Increased drooling; less saliva production & rumination
Increased CO2 expelling decrease saliva buffering
Increased panting
Acidosis related problems
LuCinda >67,941lbs./ 365 days in 1997. Previous record was 1996 – 63,444#
Record was broken after 12 mo. by another >72,000 lbs./365 days (28gallons/day)
Lynn
One lactating cow can generate 1600
Watts of heat 100 Watt
100 Watt
100 Watt
100 Watt
100 Watt
100 Watt
100 Watt
100 Watt
100 Watt
100 Watt
100 Watt
100 Watt
Energy Exchange
Metabolic Heat Production = Evaporative Heat Loss + Sensible Heat Loss
Sensible Heat Loss
If T environment < Tskin
there will be heat loss
Sensible Heat Loss = Convection + Radiation + Conduction
Evaporative Heat Loss
EHL
Water vapor
Conduction
T ground = 35°C T skin = 35°C
T skin = T ground
No Heat Exchange
Conduction
T ground = 38°C T skin = 35°C
HEAT GAIN
Conduction
T ground = 29°C T skin = 35°C
HEAT LOSS
Convection
FAN
T air = 32°C
T skin = 35°C
HEAT LOSS
Convection
FAN
T air = 37°C
T skin = 35°C
HEAT GAIN
Convection
FAN
T air = 35°C
T skin = 35°C
T skin = T air
No Heat Exchange
Radiation
T roof = 40°C
T skin = 35°C HEAT GAIN
Radiation
T roof = 32°C
T skin = 35°C HEAT LOSS
Cows are not good at sweating
At high environmental temperatures heat loss depends upon evaporation
because heat loss by sensible heat loss becomes small as environmental temperatures approach skin
temperatures
Cows are not good at sweating
Typical sweating rates
Cows: 400 g/m 2 h Humans: 1000 g/m 2 h Horses: 2000 g/m 2 h
TemperatureHumidity Index (THI) RELATIVE HUMIDITY, % 0 F 0 C 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 69.8 21 64 64 64 65 65 65 66 66 66 67 67 67 68 68 68 69 69 69 70 70 71.6 22 65 65 65 66 66 67 67 67 68 68 69 69 69 70 70 70 71 71 72 72 73.4 23 66 66 67 67 67 68 68 69 69 70 70 70 71 71 72 72 73 73 74 74 75.2 T 24 67 67 68 68 69 69 70 70 71 71 72 72 73 73 74 74 75 75 76 76 78.8 E 26 68 68 69 69 70 70 71 71 72 73 73 74 74 75 75 76 76 77 77 78 80.6 M 27 69 69 70 70 71 72 72 73 73 74 75 75 76 76 77 78 78 79 79 80 82.4 P 28 69 70 71 71 72 73 73 74 75 75 76 77 77 78 79 79 80 81 81 82 84.2 E 29 71 71 72 73 73 74 75 75 76 77 78 78 79 80 80 81 82 83 83 84 86.0 R 30 71 72 73 74 74 75 76 77 78 78 79 80 81 81 82 83 84 84 85 86 87.8 A 31 72 73 74 75 76 76 77 78 79 80 81 81 82 83 84 85 86 86 87 88 89.6 T 32 73 74 75 76 77 78 79 79 80 81 82 83 84 85 86 86 87 88 89 90 91.4 U 33 74 75 76 77 78 79 80 81 82 83 84 85 85 86 87 88 89 90 91 92 93.2 R 34 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 96.8 E 36 76 77 78 79 80 81 82 83 85 86 87 88 89 90 91 92 93 94 95 96 98.6 37 77 78 79 80 82 83 84 85 86 87 88 89 90 91 93 94 95 96 97 98 100.4 38 78 79 80 82 83 84 85 86 87 88 90 91 92 93 94 95 97 98 99 100 102.2 39 79 80 81 83 84 85 86 87 89 90 91 92 94 95 96 97 98 100 101 102 104.0 40 80 81 82 84 85 86 88 89 90 91 93 94 95 96 98 99 100 101 103 104 105.8 41 81 82 84 85 86 88 89 90 91 93 94 95 97 98 99 101 101 103 105 106 107.6 42 82 83 85 86 87 89 90 92 93 94 96 97 98 100 101 103 104 105 107 108 109.4 43 83 84 86 87 89 90 91 93 94 96 97 99 100 101 103 104 106 107 109 110
Comfortable Alert Danger Emergency
THI for Cattle
http://www.novalynx.com/referenceheatindex.html
64
66
68
70
72
74
76
78
Dairy 1 Dairy 3 RFP
69.2 lbs
31.5 kg
73.1 lbs
33.2 kg
76.4 lbs
34.7 kg
Dairy 1 – Just shade without misters/sprayers
Dairy 3 – Shade with misters at the feed area
RFP – Free stalls with water spray at the feed area
Daily milk production per cow in 3 related farms (owned by the same family) within the same area from June – October, 2000. California.
http://www.bae.uky.edu/ext/Livestock/Dairy/PDFs/KSU_heatstress.pdf
Shade for dairy cows is a necessity! Structural design is important.
37.8
38.0
38.2
38.4
38.6
38.8
39.0
39.2
11:00 11:30 12:00 12:30 13:00 13:30 14:00 14:30 15:00
Time of Day
Tvag
ina, °C
0.50 °C/hr
0.69 °C/hr 1.02 °C/hr 0.84 °C/hr
Lying in stall Lying in stall
Standing under feed line spray
Standing dry
Standing under feed line spray
Lying vs Standing under water spray
When body temperature reaches 39°C cow stands and seeks cooling
Experimental system to cool cows while lying in stalls
Ultrasonic cow detector
Spray during lying
Activity
Rate of change in Tvagina, °C/hr
Standing: feed line spray Standing: no spray Lying: stall spray Lying: no spray
1.0
0.5
0.0
0.5
1.0
95% CI for the Mean
Effect of spray on body temperature
0.8
0.6
0.4
0.2
0
0.2
0.4
0.6
0.0 0.5 1.0 1.5 2.0 2.5
Airflow, m/s
Ch
an
ge
in
Tre
cta
l,
°C/h
r
NO WET
LOW WET
HIGH WET
Cooling Effect of Wetting and Airflow on Body Temperature
Examples of the cooling system in farm B and C. Farm A only had limited shade for animals.
Farm B
Farm C
Oscillating fans
Koral Kool fans
Farm A
Shade Structures
Oscillating fans
Foggers over mangers and shade
Schaffer Fans and Shade
12600 12800 13000 13200 13400
13600 13800 14000 14200 14400 14600
Dairy A Dairy B Dairy C
Milk Production (Kg. per lactation on mature equivalent)
The Use of Water and Shade over the Feed Manger.
0
10
20
30
40
50
1st 2nd 3rd 4th
%
47.6
41.3 37.5
25.0
Conception rates of cows bred in sequence when 4 straws of semen were thawed at the same time in the subtropics without shade over the feed manger.
Breeding sequence
The Use of Shades, Fans and Misters
NOT ALL FANS DO THE JOB OF COOLING
Pen of High Producing Cows (n=25)
Uterine blood flow in the (a) gravid and (b) nongravid horns during standing ( ) or lying ( ) positions on d 226, 248, and 267 of gestation. Data are means ± SE during 23 h for 4 (d 226) or 7 (d 248 and 267) pregnant Holstein cows. Numbers above each bar are the mean uterine blood flows (L/min). **P < 0.01, *P < 0.05, and < 0.10 illustrate differences between the 2 postures within day of gestation
Nishida, T. et al.
JDS 2004. 87:23882392
Why is the polar bear in the artic white and the majority of the goats in the desert dark or black in color?
Regression of White Cow Population Farm A (4 7> lactations)
4 5 6 7 0
5
10
15
20
Y = 19.0 3.58 X RSquared = 0.813
Regression of Black Cow Population Farm A (4 6 lactations)
4 5 6 50
55
60
65
70
75
80
0
2000
4000
6000
8000
10000
12000
White BnW Black
Farm A
Farm B
11806 11511
9907 9593
Milk production (kg) between white, blackwhite and black cows in Waianae. Cows were a min. of 4 lactations or higher.
90% ~50:50% 90% Farm A – 215/960
Farm B – 690/1350
0
5
10
15
20
White Hair Black Hair
Length of long hair in different color Holstein
0
0.2
0.4
0.6
0.8
1
1.2
1.4
White Hair Black Hair
Color of Holstein
Leng
th in
cms
Weight of hair (ug/cm 2 )
The data suggest that:
a) Black hair was shorter
b) Probably more fine
The combine characteristics allow for greater evaporative cooling.
[these hair measurements were samples taken from the thurl region]
Hair coat color and eye pigmentation
Conducting Heat Stress Studies With Feedlot Cattle, measuring evaporative cooling via sweating, 2004.
The Relationship of Hair Coat Score and Total Weight Gain In Cattle.
Turner and Schleger, 1959.
Hair Coat Score:
1 extremely short, thin
4 fairly long
7 woolly
1 pt change amounts to 25 pounds
1pt change amounts to 25 pounds.
Measuring solar radiation, uv wave length, core body temperature in relationship to hair coat color and hair length, MS 2005.
How do cows cool themselves in nature in a place where the avg. wind speed exceeds 14mph?
Some water dripping on the side.
The Udder is innervated
Little research has been done on cooling the udder other than when the cows are in the holding pen.
Take Home Lessons: • Heat stress affects milk production, reproduction and immunology in cattle
• Signs of heat stress are: standing, panting/increased respiration and drooling.
• Provide animals protection from solar radiation, modify environment, make adjustment in nutrition, select the right breed, etc.
• Always weigh the economic costs of each program (input vs return).
• No silver bullet for all farms but apply principles correctly to gain best results.
American
Jerseys
