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Cool Cows and Climate Change - Information for Dairy Farmers
Metabolic and environmental heat
Heat load
Heat exchange in cows
Off-loading heat

Cows & Heat

Metabolic and Environmental Heat

Cows generate heat internally (metabolic heat) as a result of eating and digesting feed. Like most mammals, the dairy cow needs to maintain its core body temperature within a narrow range around 39oC – between 38.6oC and 39.3oC to be precise! The core temperature fluctuate slightly throughout the day, reaching a peak in the early evening and a low early morning. 

Cows also take on heat from the environment around them.

The cycle of gaining and losing heat absorbed from the environment is on-going and always operates in the context of the metabolic heat a cow is carrying at any given time. Factors that determine the level of environmental heat a cow fains or loses over time are:

  • air temperature and relative humidity;
  • amount of solar radiation;
  • degree of night cooling the occurs;
  • ventilation and air low; and
  • length of the hot conditions.

Cows have evolved a range of physiological strategies to off-load heat to cope in hot environmental conditions but problems occur if temperatures and humidity are high (and remain high) and cows do not have opportunities to get rid of load heat.

Cows generate and absorb heat

Australian Government - Department of Agriculture, Fisheries and Forestry