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Extension > Agriculture > Dairy Extension > Calves and heifers > Keeping your calves cool and comfortable in the summer

Keeping your calves cool and comfortable in the summer

Neil Broadwater

Published in Dairy Star May 14, 2010

Reducing heat stress in calves may not be the top concern during the 'dog-days' of summer, but it should be high on the priority list. Certainly, the milking herd needs to be tended to and managed so they are comfortable and can maintain milk production levels. But, what affect does very hot weather have on the well being of a calf? The consequences won't be noticed immediately as with milk production, but the health and growth rate of calves under heat stress are at stake.

Heat stress occurs with high ambient temperature, high relative humidity and excessive radiant energy that prevent adequate heat loss by animals. Although used as a reference for heat stress in dairy cows, the Temperature-Humidity Index (see table*) can still be fairly relevant and meaningful for dairy calves as well.

chart showing temperature humidity index

*Modified from Dr. Frank Wiersma (1990), Dept. of Ag. Engineering, U of AZ.

Calves do best when the optimal thermal environment is between 55 to 78°F in still air. Above 78°F, calves must burn more energy to drive off heat from the body by sweating and increasing respiratory rate. There is reduced feed intake and less of the nutrients consumed are devoted to growth. A further consequence is that calves can then experience a rise in body temperature (103 to 108°F can mean very sick calves), rapid dehydration, and a weakened immune system. Signs of heat stress in calves include: reduced movement, decreased feed intake, increased water consumption, desire for more shade, rapid respiration/panting, open-mouth breathing, lack of coordination.

The following are some management practices to keep calves healthy and to have acceptable rates of gain during hot and humid weather:

There can be economic consequences to not managing heat stressed calves properly. A slower rate of gain means a longer time before that calf gets into the milking string. Calves and heifers are an expensive enterprise in a dairy operation and they represent the dairy farm's future. Their care and management should be a high priority during the hot summer months.

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