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Reducing heat stress in hutch calves

By Dale A. Moore, DVM, MPVM, PhD; Jen Duprau; and John R. Wenz, DVM, MS

Looking for a simple way to help hutch calves cope with summer heat stress? In a trial we conducted in the summer of 2011 in central Washington, we tested one method to try to improve air circulation within calf hutches to reduce hutch temperatures.

Why look at heat stress remediation? Heat stress affects calf health, growth, and welfare. The calf’s “comfort zone” is fairly narrow, and temperatures above 90⁰F with moderate humidity can put calves under stress. Studies looking at different types of housing show some hutches are better than others at keeping temperatures down by providing shade, but many calves are still challenged with heat stress regardless of the type of hutch.

Placing shade cloth over hutches is effective at reducing temperatures just as it does with adult cows. Making sure calves have plenty of fresh water also helps them cope with heat, and orienting hutches to the north in summer to maximize shade can also help. What else?

Many dairy advisors have recommended placing a concrete block under the hutch to improve airflow but no one had ever tested this method to see if it did what it was supposed to. We evaluated 15 calf hutches on one dairy over a 48-hour period. We installed temperature and humidity data loggers in each hutch and placed one outside, providing us with hourly measures. Three times a day we evaluated internal and external hutch carbon dioxide levels (a sign of problems with fresh air circulation), measured airflow, and observed calf respiratory rates. For the first 24 hours, the plastic hutches stayed snug on the ground. For the next 24 hours, they were elevated with an 8-by-8-by-16-inch concrete block.

What did we see?

  • Calf respiratory rate was higher with higher internal hutch temperature. For every 1⁰C increase in internal hutch temperature, respiratory rate increased by two breaths per minute.
  • At the hottest times of the day, internal hutch temperatures were higher than outside temperatures when the hutch was on the ground. Internal hutch temperatures were lower than outside when the hutch was elevated.
  • Elevating the hutch improved air movement within the hutch.
  • Hutch elevation lowered afternoon respiratory rates in the calves (58 vs. 44 breaths per minute; P <0.05).
  • Carbon dioxide levels were lower when the hutch was elevated.

Calf respiratory rate can indicate a level of heat stress. In the late afternoon, elevating the hutch lowered the temperature and subsequently, the respiratory rates of the calves. Decreasing carbon dioxide levels within the hutches is important because the concentration of this gas is associated with poor ventilation. The evidence for internal air movement is also an indication of better ventilation from elevating the hutch. Improving ventilation and reducing heat are both important to calf health and welfare. Dairy producers now have another validated choice to remediate summer heat stress in calves.

References

  • Broucek, J., Kisac, P., and P. Uhrincat. 2009. Effect of hot temperatures on the hematological parameters, health, and performance of calves. Int. J. Biometeorology. 53:201-208.
  • Lammers, B.P., vanKoot, J.W., Heinrichs, A.J., and R. E. Graves. 1996. The effect of plywood and polyethylene calf hutches on heat stress. Appl. Eng. Agric. 12:741-745.
  • Moore, D. A., Duprau, J., and J. R. Wenz. 2012. Effects of dairy calf hutch elevation on heat reduction, carbon dioxide concentration, air circulation and respiratory rates. J. Dairy Sci. (In Press)
  • Spain, J.N. and D. E. Spiers. 1996. Effects of supplemental shade on thermoregulatory response of calves to heat challenge in a hutch environment. J. Dairy Sci. 79:639-646.
  • Stott, G.H., Wiersma, F., Menefee, B.E., and F. R. Radwanski. 1975. Influence of environment on passive immunity of calves. J. Dairy Sci. 59:1306-1311.