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Detecting heat stress in hutch-housed dairy calvesDetecting heat stress in hutch-housed dairy calves

Heat stress, even in the northern US, can be a concern during summer months.

June 1, 2023

6 Min Read
Detecting heat stress in hutch-housed dairy calves


There is a dearth of data on heat stress in dairy calves.  Yet, calves may be more prone to heat stress than cows because they like human infants have limited ability to regulate body temperature, and they have a greater surface area per unit body mass than cows.  As with cows, many may assume that heat stress in calves is not significant in the northern United States climate.  A subtropical study (Daddo-Senn et al., 2020) found that temperature-humidity index (THI) breakpoints were 65, 67, and 82 at which respiration rate (RR), rectal temperature (RT), and DMI, respectively, begin to change.  According to the most recent NAHMS survey (2014), calf hutch systems accounted for approximately 63% of all calf housing in the United States with 25% indoor and 38% outdoor.

That led to a study in Wisconsin (Dado-Senn et al., 2023) to establish associations between and thresholds for environmental and animal-based indicators of heat stress in Holstein dairy calves individually hutch-housed across a continental climate summer. This was achieved  through assessing correlations between dairy calf animal-based (i.e., respiration rate (RR), rectal temperature (RT), and skin temperature (ST)) and environmental indicators, air speed (AS), relative humidity (RH), and multiple THI equations.

The study was done from June 14 to August 10, 2021 with 63 female Holstein calves in sand-bedded polyethylene calf hutches.  Shade proved by a calf hutch and its rear ventilation were the only heat-abatement factors in this study.  Following 4 quarts of colostrum at birth, calves were fed twice daily 4 liters of pasteurized milk and free choice grain and water.  Calves began the study on a rolling basis at 14 days of age and finished at 42 days of age.  Wire paneling restricted a calf to its own hutch area.  Details about animal measurements, environmental measurements, and statistical analyses are contained in the paper (Dado-Senn et al., 2023).          

Data in Figure 1 indicate:

  • Considerable day-to-day variability within measurements

  • Average daily ambient dry bulb minimum temperature (16.3/61.3 C/F, THI = 60.8) occurred on July 8

  • Average daily ambient dry bulb maximum temperature ( 27.6/81.7 C/F, THI = 77.3) occurred on June 11

  • Average THI across the experimental period (June to August) was 69.7 (Figure 1C)

  • Of daily THI1 averages, 91% remained above a THI of 65, which is a previously established threshold for heat stress indicator in dairy calves in a subtropical climate (Dado-Senn et al., 2020).

  • The average daily dry bulb temperature across the experimental period was 22.6/72.7°C/F (Figure 1C)

  • Of daily dry bulb temperatures averages, only 20% remained above the suggested upper critical temperature of 25/77°C/F in the calf thermoneutral zone

  • Daily minimum for dry bulb temperature, black globe temperature, and THI occurred between 0400 and 0500 hours and averaged 16.9/62.4°C/F, while daily maximum was between 1500 and 1600 hours, which averaged 27.8/82.0°C across the experimental period

  • Relative humidity maximum and minimum were the inverse at these times

  • Hutch external and internal air speed were also highly variable but averaged 0.96 meter/second and 0.03 meters/second, respectively

Al_20June_20-_201.pngFigure 1. ChartDescription automatically generated

Breakpoints are indicated in Figure 2 for respiration rate, rectal temperature, and THI:

  • For respiration rate, calves had a dry bulb temperature breakpoint of 21/70°C/F

  • THI breakpoint of 69, whereby respiration rate began rising above 40 breaths per minute (bpm) at a rate of 1 bpm for every unit increase in THI or 2 bpm for every unit increase in dry bulb temperature above the threshold

  • Respective breakpoints for rectal temperature (RT) were 21.5/70.7°C/F dry globe temperature and 69 THI, whereby RT began rising above 38.5/101.3°C/F at a rate of 0.02 or 0.04/0.036 or 0.072°C for every unit increase in THI or dry globe temperature above the threshold, respectively.

  • No breakpoints were detected for unshaved skin temperature or shaved skin temperature within the ambient environment range measured in the present study (i.e., dry globe temperature = 15 to 35/59 to 138 °C/F or THI = 60 to 90).

  • However, the corresponding shaved skin temperature and shaved skin temperature values relative to the RR and RT thresholds for dry globe temperature were 27/82°C/F and 32/90°C/F, respectively


We must also realize that these results apply only to the specific calf hutch used in this study (disclosure, I have done consulting work in the past for the company which makes that hutch).  I am aware of some other unpublished work which shows interior hutch temperatures differ among different configurations and manufacturers of calf hutches.  Also, shading hutches can make significant differences in inside hutch temperatures.

I am also aware of some work done to put individual shades over hutches, but cost, types of material, and labor required have kept that from being practical.  Shade has also been shown to be useful in reducing ambient temperate for heifers (Marcillac-Emberson et al., 2009; Kertz 2009; Kertz 2019, p. 108-111),

Lastly, a study in which the rear of hutches was propped up with concrete blocks found that while the normal range was 24 to 36 respirations per minute by calves, this propping up reduced respirations from 58 to 44 per minute during heat stress (Moore et al., 2012).  And respirations increased by 2 per each increase of 1º C inside the hutch temperature.

The Bottom Line

Heat stress is a real problem for dairy calves even in the northern US. Generally, the zone of thermal neutrality in young dairy calves is from 15 to 26 (59 to 79) C/Fº (NASEM 2021).  This study showed that during the summer months in Wisconsin, heat stress occurred 91% of the time inside calf hutches based on a THI of 65.  The average daily dry bulb temperature across the experimental period was 22.6/72.7°C/F, and only 20% remained above the suggested upper critical temperature of 26/79°C/F in the calf thermoneutral zone.


Dado-Senn, B., V. Ouellet, G. E. Dahl, and J. Laporta. 2020. Methods for assessing heat stress in pre-weaned dairy calves exposed to chronic heat stress or continuous cooling. J. Dairy Sci. 103:8587– 8600.

Dado-Senn, B., V. Ouellet, V. Lantigua, J. Van Os, and J. Laporta.  2023.  Methods for detecting heat stress in hutch-housed dairy calves in a continental climate.  J. Dairy Sci. 106:1039–1050.

Kertz, A. F. 2009.  Effects of shade on heifers evaluated.  Feedstuffs. July 13, p. 12-13

Kertz. Alois F. Dairy Calf and Heifer Feeding and Management—Some Key Concepts and  PracticesOutskirts Press, July 31, 2019, 166 pages.

https://outskirtspress.com/dairycalfandheiferfeedingandmanagement Marcillac-Embertson, N. M., P. H. Robinson, J. G. Fadel, and F. M. Mitloehner.  2009.   Effects of shade and sprinklers on performance, behavior, physiology, and the environment of heifers.   J. Dairy Sci. 92:506-517.

Moore, D. A. , J. L. Duprau, and J. R. Wenz.  2012. Short communication: Effects of dairy calf hutch elevation on heat reduction, carbon dioxide concentration, air circulation, and respiratory rates. J. Dairy Sci. 95 :4050–4054.

National Animal Health Monitoring System.  Dairy 2014.  Dairy Cattle Management Practices in the United Sates. United States Dept. of Agric., Animal Plant and Health Inspection Service, Veterinary Services, February 2016, Fort Collins, CO. https://www.aphis.usda.gov/animal_health/nahms/dairy/downloads/dairy14/Dairy14_dr_Mastitis.pdf

National Academies of Science Engineering Medicine (NASEM). 2021. Nutrient Requirements of Dairy Cattle, Eighth Revised Edition. Washington, DC. 

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