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Prepare now for summer feeding program

Jim Linn and Mary Raeth-Knight

Published in Dairy Star May 2007

The hot days in May are a reminder that the heat of summer is coming. As we move into June, July, August and even September, the hot days of summer will challenge our dairy cows. It is not too early to begin making changes in your diets to help cows manage the stresses of heat and humidity.

When cows actually feel heat stress is a function of both temperature and humidity. In very dry conditions, 10 to 20% humidity, cows may not show signs of heat stress until temperatures are in the mid to upper 80s. In very humid conditions, above 75%, heat stress can start at 70 degrees. Research from the University of Georgia a few years ago found a lag of about two days between heat stress conditions and when cattle showed the signs of heat stress. Indicators that cows are experiencing heat stress are:

Dietary modifications will help cows cope with heat stress, but diet has a far less impact on mitigating heat stress than does altering the environment. Sprinklers, fans and shade are much more important for heat abatement than diet change. Nevertheless, nutritional alterations in the diet can help reduce heat stress. The three areas to focus on with diet changes are feed intake, energy intake and keeping cows healthy.

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