This document summarizes the impact of heat stress on dairy cow fertility and milk production based on research conducted in Israel. Some key points: - Heat stress reduces dairy cow fertility by decreasing estrus intensity and disrupting follicle development, oocyte competence, embryo development, and progesterone secretion. - Cooling cows using shade, fans, sprinklers and frequent misting can help prevent declines in milk production during heat stress, but does not eliminate reductions in reproduction. - Additional strategies like follicle aspiration to induce follicular turnover and progesterone supplementation may help improve summer fertility. A large-scale Israeli study found intensive cooling (10 periods per day) significantly improved conception rates compared to minimal or moderate cooling.

1. Zvi Roth (Ph.D.)
Department of Animal Science, Faculty of Agriculture, The Hebrew
University of Jerusalem, Israel
The impact of heat stress on
fertility and milk production
- the Israeli experience
SIRAA, Londrina, Brazil 2018

2. Introduction
• Heat stress - a worldwide problem
 About 60% of the world cattle population is
located in hot or warm regions
 About 35° north and south of the equator

3. Introduction
• The problem of heat stress is growing
 Global worming
 Increases in milk yield
 Greater metabolic heat production

4. Milk production in Israel
* 14,000 kg/ cow/lactation *

5. Heat production is related to milk level
0 10 20 30 40 50
10
20
30
40
Mcal/day
Milk production (kg/day)

6. Heat production Heat loss
Thermal Status

7. • Increase in respiratory and hart rate
• Increase in oxygen consumption
• Vasodilation
• Decrease in feed intake
• Decrease in rumination
• Decrease in activity
• Increase in standing time
• Increase in body temperature
Physiological and behavioral changes
in dairy cows under heat stress

8. 1) Panting
• Respiratory evaporation
In cattle, is not an efficient
channel of heat loss.
It constitutes about 25% of
total water loss
Heat -Loss via Evaporation
2) Sweating from skin surface.
It constitutes about 75% of total water loss.

9. Sweating rate, in cattle, is relatively low
compared to humans and horses
Cow Man Horse
0
300
600
900
1200
1500
g/hxm2

10. Hyperthermia is unavoidable !!

11. • Increased postpartum disorders
• Reduced fertility
• Prolonged calving interval
• Increased culling rate
Causing heavy economic loos !
Productive and reproductive losses in
dairy cows under hot-climate

12. 24.0
26.0
28.0
30.0
32.0
34.0
36.0
38.0
40.0
Jan-FebJan-Feb
Jul-Aug
Milk production of cows calved in the winter
vs. summer (1st lactation)
Milk(kg)/day
Days after calving
Reduced milk production

13. 24.0
26.0
28.0
30.0
32.0
34.0
36.0
38.0
40.0
42.0
44.0
46.0
48.0
Jan-Feb
Jul-Aug
Milk production of cows calved in the
winter vs. summer (2nd lactation)
Milk(kg)/day
Days after calving
Reduced milk production

14. 2.90
3.00
3.10
3.20
3.30
3.40
3.50
3.60
Jan Feb Mar Apr May Jun Jul Ago Sep Oct Nov Dec
(%)
Month
Fat
Protein
Fat and protein in milk
Reduced milk contents

15. 250
270
290
310
330
350
370
390
410
Jan Feb Mar Apr May Jun Jul Ago Sep Oct Nov Dec
Month
SCC(thousands) Somatic cell count (SCC)
Increased somatic cell count ( SCC)

16. What can we do to alleviate
the effects of heat stress?
Heat production Heat loss
?

17. • Concentrate energy and adjust protein.
• Use high-quality forage and reduce its proportion.
• Replace roughage components with by-products
rich in digestible NDF, such as soy hulls.
• Taking into account the mineral losses (Na, K) via
sweating and urinary excretion.
Feeding approaches to alleviate the
effects of heat stress

18. Control the time of metabolic heat production
throughout the day
• Feed more frequently with fresh food
• Feed in the evening or at night
Feeding time
Adin et al, LS 2008; Adin et al, LS 2009; Adin et al, JDS 2009;
Miron et al, AFST 2009

19. Feeding
manipulations
- 13%Respiratory rate (min-1)
- 0.3Rectal temperature (oC)
+ 8.3%Voluntary DMI (kg/day)
+ 0.05BCS change (1-5 scale)
+ 6.2%Milk yield (kg/day)
Adin et al, 2008
Alleviation the effects of heat-
stress by feeding

20. Using of cooling methods to reduce
the effect of heat stress
1) Without the use of water
(shading, fans)
2) With the use of water
Classification:

21. Modern shade structures
(high roof & good ventilation)

22. Using of shade structures in the
resting area and feeding line

23. Shading the feeding line to avoid direct
solar radiation and food fermentation

24. Shading the water troughs to
ensure fresh and clean water

25. Using of simple shade structures in
the south of Israel
*

26. Effect of shade on the body
temperature (Tb)
Tb
No shade
Shade
NightDay Day
(Berman, 2004)

27. Hade and Respiratory rate
Respiratoryrate
THI

28. Effect of provision of shade to low-
milk-yielding cows in summer (Florida, USA)
Shade No shade
Air temperature 29 °C 41 °C
Body temperature 39.2 °C 40.8 °C
Respiration 83 133
pH 7.4 7.5
Food DMI (kg/day) 20.7 16.8
Milk (kg/day) 19.4 17.0
Milk protein (%) 3.37 3.29

29. Fans

30. Effect of wind velocity on skin
evaporation
Skinevaporation
20°C 40°C30°C
High velocity
Low velocity
(Berman, 2004)

31. Heatlossfrom
theskin
20°C 40°C
m/s1
2 m/s
30°C
The effect of wind velocity on heat loss
(Berman, 2004)

32. Fans in the resting area

33. HVLS
High-volume, low-speed

34. Nevertheless, provision of shade &
ventilation does not prevent
hyperthermia in high-lactating cows !!

35. 2. Using water to cool cows
The two main applications in Israel
• Indirect cooling
• Direct cooling

36. Foggers in the resting area

37. Cooling cows in the holding area

38. Aactive only when
cows approach the
feeding line to eat:
1) when fresh food is
offered
2) after milking
3) after cooling in the
holding area of the
milking parlor
Along the feeding line

39. Body temperature of cows cooled
by sprinkling and ventilation
06:00 11:00 13:00 16:00 19:00 23:00 02:00
Day time
38.0
38.5
39.0
39.5
40.0
Bodytemperature(C)
Cooled
Non-cooled

40. Lactation curve of cooled and
control first-calving cows
Production(kg/day)
20
22
24
26
28
30
32
34
36
38
40
1 2 3 4 5 6 7 8 9 10 11
Months after calving
Cooled cows
Control cows
Flamenbaum & Ezra, 2001
(14 herds; 4000 cows)

41. Production(kg/day)
20
25
30
35
40
45
50
1 2 3 4 5 6 7 8 9 10 11
Months after calving
Cooled cow
Control cows
Lactation curve of cooled and
control multiparous cows
Flamenbaum & Ezra, 2001

42. No cooling
37.80
38.00
38.20
38.40
38.60
38.80
39.00
39.20
39.40
39.60
39.80
40.00
40.20
40.40
1
26/11/13
Time
VaginalTemperature(OC)
9:10 11:10 13:10 15:10 17:10 19:10 21:10 23:10 1:10 3:10 5:10 7:10
Vietnam
Kaim M, Vietnam, 2013
Country Temperature
(%)
Rainfall
(mm)
Relative humidity
(%)
THI
Vietnam 26 1949 78 80

43. In the milking parlor
Cooling in the feeding Line
Cows were cooled 5 times at
the milking parlor+ in the
feeding lane
37.8
38
38.2
38.4
38.6
38.8
39
39.2
39.4
39.6
39.8
40
40.2
40.4
9:10 11:10 13:10 15:10 17:10 19:10 21:10 23:10 1:10 3:10 5:10 7:10
MILKING FEED LANE
Time
VaginalTemperature(OC)

44. Cooling 5 times a day
37.80
38.00
38.20
38.40
38.60
38.80
39.00
39.20
39.40
39.60
39.80
40.00
40.20
40.40
9:10 11:10 13:10 15:10 17:10 19:10 21:10 23:10 1:10 3:10 5:10 7:10
27/11/13 MILKING FEED LANE
Time
VaginalTemperature(OC)

45. Hours
Bodytemperature(°C)
The importance of night cooling
07032321
38.5
39.5 No night cooling
Night milking
Cooling

46. Frequency of cooling
37.80
38.00
38.20
38.40
38.60
38.80
39.00
39.20
39.40
39.60
39.80
40.00
40.20
40.40
9:10 11:10 13:10 15:10 17:10 19:10 21:10 23:10 1:10 3:10 5:10 7:10
27/11/13 MILKING FEED LANE
Time
VaginalTemperature(OC)

47. • Dairy cows under heat load were cooled 5 or 8 times
sessions.
• Each cooling period lasted 45 min, comprising cycles
of 30 s of showering and 4.5 min ventilation.

48. Intensive cooling improves
production performance
5 CS 8 CS P-value
DMI, kg/day 24.7 27.0 <0.001
Milk, kg/day 36.6 40.1 <0.001
FCM (4%), kg/day 32.4 36.0 <0.001
Honig et al, 2012

49. Intensive cooling improves
physiological features
5 CS 8 CS P-value
Rumination time,
min/day
410 440 <0.001
Respiration time
breaths/min
(afternoon)
83.0 50.0 0.001
Rectal temp. (oC) 39.3 38.2 <0.001
Honig et al, 2012

50. Intensive cooling increases lying time
and decreases standing time
5 CS 8 CS P-value
Total lying time, min/day 474 484 0.004
Standing time, min/day 834 807 <0.001
Honig et al, 2012

51. • ‘Minimal’
3 wetting periods (before each milking)
• ‘Moderate’
Cooling in the ‘holding pen’
6 cooling periods, 45 min each
total of 4.5 h/day
• ‘Intensive’
Cooling in the ‘holding pen’ + ‘feeding line’
10 cooling periods, 45 min each
total of 7.5 h/day
A large-scale survey evaluating the
effect of three levels of cooling intensity

52. Milk production (mature cows)
Minimal Moderate Intensive
Winter (kg/day) 38.6 41.4 40.6
Summer (kg/day) 35.0 39.8 40.0
Difference (W-S) 3.6c
1.6b
0.6a
Ratio (S/W) 90.7% 96.1% 98.5%

53. Minimal Moderate Intensive
Winter (%) 43.5 a 45.8 a 46.6 a
(n) (618) (267) (684)
Summer (%) 16.7 c 34.5 b 33.8 b
(n) (222) (172) (572)
Conception rates from first AI
(mature cows )
Ratio (S/W) 38.3% 75.3. % 72.5%

54. • Cooling is the predominant strategy used today to
alleviate the effect of heat stress in dairy farms.
• Cooling can prevent the decline in milk production
in high-yielding cows but it cannot eliminate the
decline in reproduction during the hot season.
• Additional strategies for improving
reproductive responses under heat
stress.
Summary II

55. Effects of heat stress on
reproductive function
• Reduction of the intensity
and duration of estrus
• Attenuation of follicular
development
• Disruption of oocyte
competence
• Disruption of embryonic
development
• Reduction of progesterone
secretion
Fertility

56. Potential strategies to improve
summer fertility in dairy cows
• Synchronization program
• Follicular turnover
• Progesterone supplementation
• Embryo transfer
• Combined treatments

57. Heat stress can affect the follicle and
oocyte during a broad window of time
P.J. Hansen, 2013

58. Heat stress reduces oocyte
developmental competence
Al-Katanani et al., 2002
Gendelman et al., 2010
Ferreira et al., 2011

59. Induction of follicular turnover by
follicular aspiration
Roth et al., 2003

60. Roth at al., 2004
Induction of 9-day follicular
waves using GnRH + PG
GnRH GnRH GnRH GnRH
PG PG PG PG PG PG
October
7 9 7 9 7 9 7 9 7 9 7 9
December
FF aspiration
Day of cycle:
November
FF aspirationFF aspiration

61. Aspiration of follicular fluid

62. Steroid content in the preovulatory
follicle
Roth et al., 2004

64. • In commercial dairy farms
• Farms were equipped with efficient cooling
systems
• Animals: control (n = 187), treated (n = 195)
• Cows that appeared to be in estrus were artificially
inseminated
• Pregnancy diagnostic (rectal palpation; 45 PI)
• Logistic regression, SAS: season, milk level, body
condition (BCS), somatic-cell count (SCC), no. of
lactations
Fertility study
Summer and fall, 2008-2009 (Israel)

65. Experimental design
Friedman et al., 2011 (JDS)

66. 20
30
40
50
60
Multiparous First-calving
27%
29%
53%
37%
* P<0.06
n=111 n=76 n=75n=120
Treatment with GnRH + PG improves
conception rate in first-calving cows
Control
Treatment
Conceptionrate(%)
Friedman et al., 2011 (JDS)
*

67. Low SCC
43%
33%
28%30%
0
15
30
45
n=117 n=116n=79n=70
Conceptionrate(%)
High SCC
Treatment with GnRH + PG improves
conception rate in cows with low SCC
(< 150,000)
Control
Treatment
Friedman et al., 2011 (JDS) * P<0.1
*

68. Treatment with GnRH + PG improves
conception rate in cows with low
milk production
Control
Treatment
Friedman et al., 2011 (JDS)
20
30
40
50
60
< 40 kg
Conceptionrate(%)
> 40 kg
51%
36%
30%
*
* P<0.05

69. The corpus luteum

70. Association between progesterone
level and embryonic development
0 2 4 6 8 10 12 14 16
Mann et al., 1999
0
3
6
9
12
0
5000
10000
15000
20000
0
5000
10000
15000
20000
Day in cycle 16-day embryo
Progesterone(ng/ml)
Interferont-(unitsperuterus)
Big Small

71. Day of cycle
0 3 6 9 12 15 18 21
5
1
2
3
4
6
7ng/ml
Winter
Summer (chronic stress)
Seasonal effect on progesterone
level in plasma

72. 1 3 5 7 9
Day of culture
0
200
400
600
800
1000
Winter
Summer
Luteinized thecal cells
1 3 5 7 9
Day of culture
0
200
400
600
800
1000
Winter
Summer
Luteinized granulosa cells
ng/105cells
ng/105cells
Seasonal effect on progesterone
production by follicular cells in vitro

74. • In 2 commercial dairy farms
• Farms were equipped with efficient cooling
systems
• Animals: control (n = 195), treated (n = 181)
• Cows were 124 days postpartum; 41 kg/day
• CIDR progesterone (EAZI-BREED™) was inserted on day 5 (±
1)
• Cows that appeared in estrus were artificially inseminated
• Pregnancy diagnostic (rectal palpation; 40-45 PI )
• Logistic regression, SAS (season, milk level, body condition,
somatic-cell count, no. of lactations)
Fertility study
Summer and fall, 2008-2009 (Israel)

75. Day in cycle
0
2
4
6
8
10
0 5 10 15 20
Progesterone(ng/ml)
CONTROL
CIDR
CIDR in
CIDR out
CIDR device increases plasma
progesterone level
Friedman et al., 2012 (JDS)

76. CIDR
Control
20
30
40
50
60
BCS < 2.25
27%
49%
n=64 n=71
*
*P<0.05
Conceptionrate(%)
36%
32%
n=110n=132
BCS > 2.25
CIDR device improves conception rate
in cows with BCS < 2.25 (50 days pp)

77. CIDR
Control
20
30
40
50
46%
Postpartum
disorders
25%
Healthy
36%
38%
*
Conceptionrate(%)CIDR device improves conception rate
in cows with postpartum disorders
*P<0.09Friedman et al., 2012 (JDS)

78. Combined treatment
Friedman et al., JDS 2016

79. Combined treatment improves
1st service conception rates
Treatment
Control
0
15
30
45
Conceptionrate(%)
n = 163 n = 128n = 202n = 211
36%
40%
36%
26%
Postpartum
uterine disease
Healthy
Friedman et al., 2016

80. > 2.25 ≤ 2.25
0
10
20
30
40
)%(
Control Treatment
BCS
n = 183 n = 162n = 163n = 193
30%
32% 29%
17%
Combined treatment improves
pregnancy rate, 90 days postpartum
Friedman et al., 2016

81. Effects of hyperthermia on
reproductive performance
Embryo
Follicle
Oocyte
Corpus Luteum
Low Progesterone

82. The embryo is also sensitive to heat
stress in the first few stages
P.J. Hansen, 2013

83. P.J. Hansen, University of Florida
Using ET to bypass sensitive periods

84. Effectiveness of ET for improving
fertility during heat stress
P. J. Hansen, 2013

85. Short-term exposure
of bovine embryos to
IGF-1 increases
developmental
competence of 5-day
but not 2-day embryos
IGF-1
Bonilla et al., 2011

86. Transfer of in vitro-produced
embryos precultured with IGF-1
Block et al., 2003 Block & Hansen, 2007 Loureiro et al., 2009

87. Embryo transfer (ET)
• A study performed in Brazil examined the
effect of rectal temperature on the transfer day
on pregnancy probability on day 25 of
gestation.
Vaconcelos et al., 2006

88. • Inversely related to
pregnancy rate on day
25 of gestation
• Positively related to
pregnancy loss at 46
days of gestation
Rectal temperature at
the time of ET
Vaconcelos et al., 2006

89. Summary III
• Efficient cooling management is a
prerequisite for other, additional strategies to
improve reproductive responses under heat
stress.
• Hormonal treatment combined with cooling
systems are suggested.
• Embryo transfer combined with CIDR, to
support the embryo should not be ruled
out !

90. Efficient
Cooling
Ov. Syn. ET IGF-1 GnRH GnRH/PG CIDR Antioxidants
_ _ _ _ _ _ _ _
+ + ? ?
+ + + ?
+ + + + ?
+ + + ?
+ + ?
+ + + ?
+ + ? ? ?
?

91. …….but don’t forget the cooling !
GOOD LUCK !!