By Al Kertz, PhD, PAS, DIPL ACAN
ANDHIL LLC

Calves have a zone of thermal neutrality (no additional energy needed to cool or heat within this temperature range) of about 59/15 to 77/25 ºF/C according to the 2001 Dairy NRC. The 2021 Dairy NASEM increased the upper limit to 79/26 ºF/C. But that zone is impacted by factors such as age, hair coat, wind speed, and body fat.  Newborn calves have little body fat, as low as 3 to 5% to help in insulating against cold. And before calves eat much starter, they do not benefit by heat of rumen fermentation in colder weather while that is the bane for ruminants during hotter weather. More recently, Dado-Senn (2023) found calves began to exhibit signs of thermal stress as low as 70/21 ºF/C. 

In a 2023 report (Dado-Senn et al.) documented heat stress in Holstein calves housed in outdoor hutches in Wisconsin during the summer.  In a more recent study (Dada-Senn et al., 2024) they evaluated active ventilation of Holstein calves in hutches from July 12 to 30, 2021, at the University of Wisconsin–Madison Arlington Research Station. The study was a 3 × 3 Latin square replicated 4 times (n = 12 female Holstein dairy calves) with a 4-day treatment exposure period and a 3-day resting period in between. “On Monday of each week, treatments were initiated at 1600 hours for initial exposure. Data were collected from Tuesday to Friday, and treatments were halted at 1400 hours on Friday with the resting period from Friday night until Monday morning.”  

“Calves were weighed at birth (38.5 ± 4.8 kg), fed 3.78 L of colostrum, and thereafter fed 7.6 L/day milk replacer at 0400 and 1500 hours. Starter concentrate and water were offered ad libitum inside and outside the hutch, respectively. Calves were enrolled at 22 ± 5 days of age (mean ± SD) for a total of 21 days to avoid early-life scours and weaning, which started at 49 days of age. Calves were individually housed outdoors in sand-bedded polyethylene calf hutches (Disclosure, I have consulted with this company outside the USA) at 2.1 × 1.2 × 1.4 m; length × width × height) with the option for rear-hutch ventilation through an upper panel and 2 lower window vents (diameter ~30.5 cm; Figure 1A). All calves had free access to a wire-enclosed pen (1.7 × 1.4 m) except at the time of restriction (described below). Calves remained in their individual hutch for the duration of the study, and different treatments were applied to the hutch in each period. Treatments were considered either minimal ventilation (CON; all rear-hutch ventilation closed), passive ventilation (PASS; rear-hutch upper panel opened to a 20° angle and lower window vents opened), or active ventilation (ACT; solar-powered fan placed in closed upper panel and lower window vents opened). Each replicate was grouped to make a line of 12 calf hutches, behind which 4 solar panels were placed (Figure 1C). Treatment designs are visualized in Figure 1A–C.” 

Figure 1 

“Calf position and location was assessed using day- and night vision trail cameras that took pictures every 5 min and captured 3 calves per frame. Calf position and location, including calf lying outside (OL), standing outside (OS), or being inside (IN), were identified using computer vision systems described by Negreiro et al. (2022). The darkness inside the hutch prevented algorithm differentiation between lying versus standing inside the hutch. The objective of monitoring the aforementioned behavior was to determine if calves used the ventilation system and remained inside their hutch, particularly in warmer hours of the day. The period of time when calves were restricted EXT or INT was not included in the behavioral assessment.“ 

Key Results: 

These results indicate active ventilation in these types of calf hutches was not advantageous nor would it be cost justifiable currently. 

Prior research evaluated sun reflective hutch covering to reduce interior hutch temperatures (Friend et al., 2014). While temperatures were lowered somewhat, the cost of replacing the shade material annually and labor required to install and replace shade material made that approach not practical.   A similar approach was investigated for creating warmer internal hutch temperatures during the winter (Binion and Friend 2014; Haberman et al., 2014) but was found not to be cost effective and practical. 

Lastly, Lago et al., (2006) found that indoor calf housing lacked good ventilation in some calf facilities.  There should be about 4 air exchanges hourly to avoid moisture and bacterial build-up in the air, which is particularly critical in wintertime.  

The Bottom Line 

Providing an external fan source had limited effect in calf hutches versus different size openings in the back of the hutches. But this would be dependent on the type and specifications of hutches. It is encouraging that studies are being done on ventilation to increase comfort and performance of calves, just as has been done for lactating cows. 

References

Binion, W., and T. H. Friend. 2014. Modeling the effect of reflective film calf hutch covers on reducing heat loss. J0int Annual Meeting, Kansas City, MO, J. Anim. Sci Vol. 92, E-Suppl. 2/J. Dairy Sci. Vol. 97, E-Suppl. 1, Abstract #0038, p. 18-19.

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.

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.

Dado-Senn, B., J. Van Os, J. Dorea, and J. Laporta. 2024. Actively ventilating calf hutches using solar powered fans: Effects on hutch microclimate and calf thermoregulation. JDS Communications 5:61–66.

Friend, T.H., W. Binion, and J. Haberman. 2014. Effect of 4 different reflective barriers on black globe temperatures in calf hutches and on calf ADG. J0int Annual Meeting, Kansas City, MO, J. Anim. Sci Vol. 92, E-Suppl. 2/J. Dairy Sci. Vol. 97, E-Suppl. 1, Abstract #0043, p. 22.

Haberman, A., T. H. Friend, and W. Binion. 2014. Effect of heat retaining covers on calf hutch temperature during cold weather. J0int Annual Meeting, Kansas City, MO, J. Anim. Sci Vol. 92, E-Suppl. 2/J. Dairy Sci. Vol. 97, E-Suppl. 1, Abstract #0037, p. 18.

Kertz, A. F. 2023. Detecting heat stress in hutch-raised dairy calves. Feedstuffs, June.

Lago, A., S. M. McGuirk, T. B. Bennett, N. B. Cook, and K. V. Nordlund. 2006. Calf respiratory disease and pen microenvironments in naturally ventilated calf barns in winter. J. Dairy Sci. 89:4014–4025.

NASEM. 2021. Nutrient Requirements of Dairy Cattle, Natl. Acad. Sci., Washington, D.C.

Negreiro, A., T. Bresolin, R. Ferreira, B. Dado-Senn, J. Laporta, J. van Os, and J. R. R. Dorea. 2022. Monitoring heat stress behavior in dairy calves through computer vision systems. J. Dairy Sci. 105(Suppl. 1):353. (Abstr.)

NRC. 2001. Nutrient Requirements of Dairy Cattle. Natl. Acad. Sci., Washington, D.C.