Hogeveen, H.

Miltenburg, H.D.

Poelarends, J.J.

Sampimon, O.C.

Name not available

Heat stress in a mild climate : Dutch experiences

NARCIS 

Wageningen Yield 

Hogeveen et al. 
HEAT STRESS IN A MILD CLIMATE: DUTCH EXPERIENCES 
Henk Hogeveen', Judith J. Poelarends2, Otlis C. Sampimon3 and 
Hans D. Miltenburg3 
'Farm Management Group 
Wageningen University 
Hollandseweg 1 
6706 KN Wageningen 
The Netherlands 
henk.hogeveen@alg.abe.wau.nl 
2Research Institute for Animal Husbandry 
PO Box 2176 
8203 AD Lelystad 
The Netherlands 
j.j.poelarends@pv.agro.nl 
3Animal Health Service 
PO Box 9 
7400 AA Deventer 
The Netherlands 
o.sampimon@gdvdieren.nl 
h.miltenburg@gdvdieren.nl 
Introduction 
The most comfortable environmental temperature range for dairy cows, the thermal 
comfort zone, is between 5°C and 25°C (Shearer and Beede, 1990a). When 
environmental temperature is above 25°C for an extended period, an alteration in 
basal metabolic rate is required in order to maintain normal body temperature. Dairy 
cows respond to high temperatures by seeking shade and wind, increasing water 
intake and respiration rate (Shearer and Beede, 1990a; Elvinger et al., 1991 ; Lacetera 
et al., 1996). The total body heat production of a cow is a combination of heat 
derived from normal metabolism, from the environment, and from physical and 
performance activities, such as milk production. Metabolic consequences of heat 
stress are increased heart rate (Elvinger et al., 1991), lower plasma glucose levels 
(Lacetera et al., 1996; Ronchi et al., 1999), changes in the levels of stress hormones 
(Giesecke, 1985; Collier et al., 1982; Katti et al., 1987) and an increase in rectal 
temperature (Johnson et al , 1989; Berman et al , 1985, Elvinger et al , 1991, 
Lacetera et al, 1996; Ronchi et al., 1999). In order to lower body heat production, 
cows experiencing heat stress will voluntarily reduce dry matter intake, which results 
in depressed milk production (Johnson et al., 1989; Ronchi et al, 1999; Shearer and 
7 
Proceedings of the Dutch-Israeli Seminar Robotic milking and Heat stress 
Beede, 1990b; Lacetera et al., 1996). Other factors that may play a role in milk yield 
decline, associated with heat stress, are changes in hormone levels and an increase in 
maintenance requirements (Bernabucci and Calamari, 1998; Collier et al., 1982). 
Generally, these responses decrease short-term animal performance (Shearer and 
Beede, 1990a). 
High temperatures may also affect susceptibility to infection, either by decreasing 
host resistance or by increasing the exposure to pathogens. Elevated temperature and 
high relative humidity enhance the survival and proliferation of pathogens in the 
environment. Under circumstances of heat stress, cows may lie in the alleyways of 
free stall barns or wallow in ponds, streams and mud holes in pastures, in order to 
increase heat loss. This behaviour increases the risk of infection (Shearer and Bray, 
1995). Increased milk SCC and a higher incidence of clinical mastitis in dairy cattle 
have been found in cows exposed to a hot environment (Elvinger et al., 1991 ; Collier 
et al, 1982). 
Evidence for a direct effect of elevated environmental temperature on the immune 
system is limited (Elvinger et al., 1991 ; Shearer and Bray, 1995). An indirect effect 
on immunity may occur as a result of decreased feed intake and, consequently, 
insufficient uptake of essential nutrients, which are important to optimal immune 
function (Shearer and Beede, 1990b). 
275 
250 
225 
200 
175 
150 
1997 1998 1999 2000 2001 
"i 1 r "i r H 1 r 
AVMWAWAWAV^ 
Figure 1. Development of the Dutch bulk milk cell count (arithmetic mean) from 
november 1997 until september 2001. 
Hogeveen et al. 
Heat or climate stress is a phenomenon commonly associated with extreme climatic 
circumstances such as in Israel or Arizona. However, mild stress can occur at a 
temperature of 25°C and a relative humidity of 50% (Armstrong, 1994). These are 
circumstances that do occur in mild climates such as in the Netherlands. A little more 
than 5 years ago, in the Netherlands the first signs of occurrence of heat stress were 
reported from practice. These reports were partly based on the observation that the 
bulk milk SCC seemed to be higher in summers, whereas the bulk milk SCC used to 
decrease in summers due to a decreased risk on intramammary infection since cows 
were grazed outside. Figure 1 illustrates these increases in bulk milk somatic cell 
count (Dutch arithmetic average) during summers. In summers with longer periods 
of high temperatures, such as 1997 and 1999, the average bulk milk SCC increased 
even more than in other, cooler, summers. The bulk milk SCC increased during 2000 
and 2001. This is partly caused by a change in the Dutch milk quality scheme. Milk 
price reduction used to be applied when one bulk milk tank exceeded the limit of 
400.000 cells/ml. From 2000 milk price reduction was given when the geometric 
mean of three monthly taken bulk milk SCC measurements exceeds the limit of 
400.000 cells/ml. This means that for part of the farmers the financial motivation to 
be alert on a high BMSCC is party removed. Part of the exceptional increase in 2001 
might be caused by heat stress in the months July and August. Another part might be 
caused by the exceptional circumstances due to the foot and mouth disease outbreak. 
Since the first evidence for the occurrence of heat stress in dairy cattle in the 
Netherlands, two scientific studies have been carried out to get more insight in the 
occurrence and background of heat stress in the Netherlands. This paper presents the 
results of both studies. The objective of the first study was to find statistical evidence 
for the assumed relation between hot summers and an increased BMSCC. The 
objective of the second follow-up study was to evaluate dairy cow characteristics that 
play a role in the cow's reaction to periods with increased environmental 
temperatures in a mild climate. Both studies have already been published by 
Sampimon et al. (1999) and Poelarends et al. (2000). 
Material and methods 
Study J. Relation between high temperatures and heat stress under mild climatic 
circumstances 
BMSCC and temperature data were obtained for the years 1993, 1994 and 1995. 
From each year nearly 300.000 BMSCC measurements from 23.325 farms (70 % of 
all Dutch farms) were available. These measurements came from three large dairy 
industries. Only days with more than 1.000 measurements were included in the 
study. Per day the average BMSCC was calculated and regarded as the average 
Dutch BMSCC at that moment. The temperature data were obtained from a weather 
station on research farm Aver Heino from the Research Institute for Animal 
Husbandry in the east of the Netherlands. To reduce the variation, the moving 
average from three successive days of the maximum temperature was calculated. The 
average maximum temperature and BMSCC were compared on each date in the 
Proceedings of the Dutch-Israeli Seminar Robotic milking and Heat stress 
years 1993, 1994 and 1995. The years 1994 and 1995 were years with periods of a 
high summer temperature. The year 1993 was used as a control year. 
Study 2. Dairy cow characteristics related to heat stress response 
Data of 47 randomly chosen herds, with a total of 1563 dairy cows, that participated 
in the Dutch milk recording system and measured cow SCC at least every 4 weeks, 
were used. Data were available for the years 1995 and 1997 with long warm periods 
during the summer and for the year 1996 with a moderate summer. 
The following parameters were available: cow SCC (5 categories with limits 75.000, 
150.000, 250.000 and 500.000 cells/ml), milk production (6 categories with limits 
15, 20, 25, 30 and 35 kg/day), parity (3 categories with parity 1, parity 2 and 3, and 
parity > 4) and stage of lactation (6 categories with limits 75, 125, 200, 250 and 300 
days in lactation). 
To investigate the changes in milk production and SCC during the summer, two four-
week periods in every year were defined. Per four-week period, the weighed average 
SCC was calculated. For all years, the period with the highest average SCC was 
defined as effect period. The preceding period was defined as the control period. In 
the years with a warm summer, the effect periods coincide with the higher 
temperatures, although the defined effect period starts later than the increase in 
temperature. 
The relative changes in cow SCC were calculated by dividing the SCC in the effect 
period by the SCC in the control period. The relative changes in daily milk 
production were calculated in a similar manner. The relative changes in SCC were 
log-transformed to obtain better statistical properties. The milk production index per 
cow was calculated as follows: milk production of the cow/mean daily milk 
production of the herd * 100. The milk production index was divided into 5 
categories with limits 70%, 90%, 110% and 130%. Effects of parity, stage of 
lactation, production and year on change in milk production and SCC were estimated 
using models (1) and (2). The models were fitted with the REML procedure of 
Genstat (Genstat 5, 1994). 
Results 
Study 1. Relation between high temperatures and heat stress under mild climatic 
circumstances 
In the year 1993 with no warm periods the BMSCC was stable (Figure 2). In the 
years with long warm periods, 1994 and 1995, the BMSCC was significantly 
elevated during these warm periods (Figures 3 and 4). It seemed that the periods with 
increased BMSCC lasted longer than the warm periods. Although not statistically 
checked, this could also be noticed from Figure 1. 
10 
Hogeveen et al. 
35,0 
Figure 2. Temperature ( lower line) and BMSCC ( upper line) for Dutch dairy 
herds in the year 1993. 
400 
350 
_ 300 
e 3 C 
u 
= 250 
E » 
o 
3 
CQ 
150 
50 
B 
' n 
*JX/ V A A J A / V 
nrrr V
-iV "A U 
\jr u ^V)i 
V u u N 
32 67 97 129 151 200 
Days in 1994 
229 259 290 340 
35,0 
30,0 
25,0 
.20.0 ( j 
w 
E 
10,0 u 
0,0 
•5,0 
Figure 3. Temperature (— lower line) and BMSCC ( upper line) for Dutch dairy 
herds in the year 1994. 
11 
Proceedings of the Dutch-Israeli Seminar Robotic milking and Heat stress 
400 
37 117 150 199 
Days in 1995 
282 
Figure 4. Temperature (— lower line) and BMSCC ( upper line) for Dutch dairy 
herds in the year 1995. 
Study 2. Dairy cow characteristics related to heat stress response 
In table 1, mean SCC in the effect and control period and changes in SCC both based 
on the rough data as well as on the statistical model are given per year. Results show 
that SCC increases in each year. In 1997 the increase in SCC is highest and tends to 
differ significantly from the increase in 1996, in which the increase is lowest. 
Table 1. Mean cow SCC in the control and effect periods, 
and estimated by a statistical model. 
Year Control period 
(cells/ml) 
1995 140.000 
1996 133.000 
1997 120.000 
effect period 
(cells/ml) 
154.000 
140.000 
152.000 
Changes are 
change 
10% 
5% 
27% 
based on original data 
estimated change 
8% 
3% 
15% 
12 
Hogevecn et al. 
Estimated changes in SCC for the different categories of daily milk production are 
presented in table 2. Cows with the highest daily milk production in the control 
period (>35 kg/day), have the largest increase in SCC (21%). 
The estimated changes in SCC for the different parity groups were -10%, 10% and 
28% for the parities 1, 2-3 and parity > 4 respectively. These estimations all differed 
significantly and show that the older cows have the greatest increase in SCC in the 
effect periods. 
Table 2. Estimated change in SCC for the different categories of daily milk production in the 
control periods. 
daily milk production (kg/day) <Î5 15-20 20-25 25-30 30-35 >35 
Estimated change in SCC 4% a 0% a 12%ab 4% a 13%ab 2 1 % b 
a,b
 Means with different superscripts differ significantly at P<0.05 
Table 3 presents the mean daily milk yield in the effect and control periods and 
changes in daily milk yield per year. Milk production was most decreased in 1997 
compared to 1995 and 1996. The difference between 1995 and 1997 is remarkable 
since both years had comparable warm summers. The only difference is the fact that 
the effect period was in 1997 one month later than in 1995 and 1996. 
Table 3. Mean daily milk production in the control and effect periods, 
original data and estimated by a statistical model. 
Year control period 
(kg/day) 
1995 24.7 
1996 25.8 
1997 24.9 
effect period 
(kg/day) 
23.7 
24.4 
21.8 
change 
- 4.0% 
- 5.4% 
- 12.5% 
Changes are based on 
estimated change 
-3 .3% a 
-5.6% a 
- 12.2% b 
a,b
 Means with different superscripts differ significantly at P<0.05 
Estimated changes in milk production by a statistical model for varying milk 
production indexes are presented in table 4. Milk production decrease is greatest for 
the high producing cows in a herd. 
13 
Proceedings of the Dutch-Israeli Seminar Robotic milking and Heat stress 
Table 4. Estimated change in daily milk production for the different categories milk 
production indexes in the control periods. 
"daily milk production (kg/day) <70 70-90 90-110 110- 130 >130 
estimated change in milk prod. -4.0% a - 4 . 1 % a -5 .6% a -8 .5% b -12.8% 
a,b,c
 Means with different superscripts differ significantly at P<0.05 
There was no apparent trend in effect of parity on milk production decrease. Only 
parity 1 and 2-3 differed slightly in milk yield decline. 
Discussion and conclusions 
As a first step in the Dutch research into heat stress, the anecdotal evidence of the 
relation between high temperatures and an increased BMSCC has been verified 
statistically (study 1). This means that the assumption that heat stress occurs in the 
Netherlands during hot periods seems to be true. Unfortunately humidity, an 
important factor in the occurrence of heat stress, could not be taken into the research. 
In the Netherlands, not many farmers have taken measures against heat stress. 
However, measures such as keeping the cows inside during hot periods, do seem to 
be effective. A study was carried out in which farmers with and without an increase 
in BMSCC during a hot period were asked to fill in a questionnaire. The results 
showed that farmers without an increase in BMSCC during a hot period adjusted the 
grazing routine more often than farmers with an increase of BMSCC. The most 
effective measure was to keep the cows inside during daytime (Poelarends et al , 
1999). 
In a next step (study 2), heat stress was analysed at the cow level. The data in that 
study show that during summer, milk production declined and SCC increased. The 
increase in SCC seemed to be highest during warm summers (P=0.06). Both 
summers, 1995 and 1997 were warm, but milk yield decline was significantly larger 
in 1997 than in 1995. A possible reason for this may be the fact that in 1997 the 
effect period was one month later than in 1995. Pasture quality might also have had 
an effect on the difference in milk production. High producing cows were the most 
susceptible to an increase in SCC. Based upon literature, some theories can be made 
about the physiological background of heat stress under mild climatic circumstances 
(Poelarends et al , 2000). 
It can be concluded that heat stress in mild climatic circumstances does occur. 
Moreover, the dairy cow characteristic parity and milk production are also important 
factors in the cow's reaction to mild heat stress. In order to gain more insight in the 
14 
Hogeveen et al. 
occurrence, effects and prevention of heat stress in mild climatic circumstances, 
further research should focus on the state of infection of the cows and the 
relationship with changes in SCC under mild heat stress. Further research should also 
focus on the role of certain hormones and metabolites in the responses of dairy cows 
to mild heat stress. Besides on physiological parameters, further research should also 
be directed towards cost-efficient methods to reduce heat stress in these 
circumstances. 
Acknowledgements &*• 
The authors gratefully acknowledge the Dutch Dairy Herd Improvement Association 
(NRS) and the Dutch dairy industry for the provision of the data. 
References 
Armstrong, D.V. 1994. Heat stress interaction with shade and cooling. J. Dairy Sei. 
77: 2044-2050. 
Berman, A., Folman, Y., Kaim, M., Mamen, M., Herz, Z., Wolfenson, D., Arieli, A. 
& Graber, Y. 1985. Upper critical temperatures and forced ventilation effects 
for high-yielding dairy cows in a subtropical climate. J. Dairy Sei. 68: 1488-
1495. 
Bernabucci, U. & Calamari, L. 1998. Effects of heat stress on bovine milk yield and 
composition. Zoot. Nutr. Anim. 24: 247-257. 
Collier, R.J., Beede, D.K., Thatcher, W.W., Israel, L.A. & Wilcox, C.J. 1982. 
Influences of environment and its modification on dairy animal health and 
production. J. Dairy Sei. 65: 2213-2227. 
Elvinger, F., Hansen, P.J. & Natzke, R.P. 1991. Modulation of function of bovine 
polymorphonuclear leukocytes and lymphocytes by high temperature in. vitro 
and in vivo. Am. J. Vet. Res. 52: 1692-1698. 
Genstat 5, Release 4.1 1994. Genstat 5, Reference Manual, edition 1994. Oxford 
University Press. 
Giesecke, W.H. 1985. The effect of stress on udder health of dairy cows. 
Onderstepoort J. Vet. Res. 52: 175-193. 
Johnson, H.D., Shanklin, M.D. & Hahn, L. 1989. Productive adaptability indices of 
Holstein cattle to environmental heat. Agricultural arid Forest and 
Meteorology Conference. 291-297. 
Katti, P.S., Johnson, H.D. & Gaddis, R.R. 1987. Stress effects of environmental heat 
on plasma and milk catecholamine in dairy cattle. J. Dairy Sei. 70: suppl. 1, 
123. 
Lacetera, N., Bernabucci, U. Ronchi, B. & Nardone, A. 1996. Body condition score, 
metabolic status and milk production of early lactating dairy cows exposed to 
warm environment. Rivista di Agricoltura Subtropicale e Tropicale. 90: 43-
55. 
15 
Proceedings of the Dutch-Israeli Seminar Robotic milking and Heat stress 
Poelarends, J.J., H. Hogeveen, O.C. Sampimon and J.D. Miltenburg 2000. Dairy cow 
characteristics related to heat stress response. Proceedings of the Symposium 
on Immunology of Ruminant Mammary Gland, Stresa, Italy. 
Poelarends, J.J., S. Smorenburg, H. Hogeveen, O.C. Sampimon, R.B.J. Kamphuis 
and J.D. Miltenburg. 1999. Stress by heat. High productive cows and farms 
with a low bulk milk somatic cell count are the most sensitive (in Dutch). 
Veeteelt 784-785. 
Ronchi, B., Bemabucci, U., Lacetera, N., Supplizi, A.V. & Nardone, A. 1999. 
Distinct and common effects of heat stress and restricted feeding on 
metabolic status of Holstein heifers. Zoot. Nutr. Anim. 25: 11-20. 
Sampimon, O.C, Miltenburg, J.D. & Hogeveen, H. 1998. Effects of environmental 
temperature on bulk milk somatic cell counts: Data from Dutch dairy herds. 
National Mastitis Council, 37th Annual Meeting, St. Louis, Missouri. 319-
320. 
Shearer, J.K. & Beede, D.K. 1990a. Thermoregulation and physiological responses 
of dairy cattle in hot weather. Agri-Practice. 11(4): 5-17. 
Shearer, J.K. & Beede, D.K. 1990b. Effects of high environmental temperature on 
production, reproduction, and health of dairy cattle. Agri-Practice. 11(5): 6-
17. 
Shearer, J.K. & Bray, D.R. 1995. Maintaining udder health and milk quality during 
periods of hot weather. National Mastitis Council Annual Meeting 
Proceedings. 83-88. 
16 


Heat stress in a mild climate : Dutch experiences

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