Dairy--Animal Management

REDUCING HEAT STRESS ON DAIRY COWS

If you think it's hot, your cows REALLY think it's hot. Cattle only sweat 10% as much as man and are more susceptible to heat stress than we are.

Use the following table to know when to take steps to ease stress and cool cows:

CAUTION ZONE	-	100 degrees F and 20% humidity
DANGER ZONE	-	100 degrees F and 50% humidity
LETHAL ZONE	-	100 degrees F and 80% humidity

Keep the following points in mind:

1. Cows need evaporative cooling - body sprinkling and good air movement.

2. Feed high quality forages to reduce heat of digestion.

3. Increase minerals

                           % in TRDM*
   Potassium                1.30
   Magnesium                 .30
   Added sodium, example     .50
      Salt                   .50
      Sodium bicarbonate 
      or sesquicarbonate
   *Total ration dry matter
   

4. Provide most of the ration during the cooler periods of the day to minimize heat production when temperatures are higher.

5. Add extra water to the TMR, silage or haylage if dry matter intake (DMI) drops seriously. This sometimes will increase DMI appreciably.

6. Feed ensiled items more frequently to compensate for shorter bunk life during hot weather, prevent heating and improve feed intake.

7. Feed a higher fat ration (up to 4 to 5% of the total ration DM) if a reasonable DMI (90% of usual) cannot be maintained.

8. Keep drinking water as cool as possible.

9. Consider using feed additives that have been effective in some studies, such as aspergillus oryzae, yeast and niacin.

10. Provide shade, especially over feeding areas and in pastures.

11. Provide air movement using fans and a water spray.

    Reference: R.S. Adams, Pennsylvania State University, June 1992. Taken from National Dairy Database.