This time of year, heat stress becomes a concern for every dairy farmer. Heat stress in cattle is brought on by a combination of high temperature and high humidity. The optimal outside temperature for dairy cattle is between 23ºF ( -5º C) and 65ºF (18ºC).
Effects of heat stress on the cow
The main effects of heat stress are:
- Reduced dry matter (DM) intake
- Reduced milk yield with lower fat and protein levels
- Reduced fertility and increased water consumption
To evacuate surplus heat, cows will raise their respiration rate and start panting. Combined that with increased salivation, reduces buffer capacity and augments the risk of ruminal acidosis. Cows suffering from heat stress spend two to three hours/day less lying down. This increases the chance of claw disorders and good claw health is necessary for optimal cow flow to the robot.
Measures to prevent heat stress
These measures do not only apply to lactating cows, but to dried-off cows and heifers as well.
- Water: High-yielding cows may drink up to 50 gallons (200 liters) per day. As rule of thumb, the water required by a cow equals four times her daily milk yield.
- Housing: Cows need ventilation to cool off. Natural side-ways ventilation in open-sided barns, together with mechanical ventilation from 60ºF (20°C) onwards, is the most effective.
- Feed management: Feeding more often, at cool moments of the day, keeps the ration fresh and tasty as well as stimulating feed intake and preventing fermentation.
- Pasture: During hot periods, it is advisable to have the cows in pasture only during the night or during the cool moments (evening, early morning) of the day.