Hot milk

Remember yesterday’s 41 degree Celsius heat? Now, imagine you were standing outside in it being blasted by 250 1500-watt hair dryers. How do you feel now? Ready to do athletics?

Grazing the lush crop

Icy poles for cows

Believe it or not, each of our dairy cows gives off body heat equivalent to a 1500-watt hair dryer on a hot day. Yet, incredibly, each still made an average of 29 litres of milk for us yesterday. We nursed them through with some very careful planning based on the principles of the Cool Cows program.

  • Wayne got up an hour earlier to milk before the sun’s rays began to sting and milked two hours later than usual. This meant that the cows spent less time in the sun on the concrete yard waiting to be milked.
  • We hosed the whole yard down about 45 minutes before the afternoon milking. It’s amazing how much cooler the yard felt afterwards.
  • The yard sprinklers were activated as the cows came towards the yard. (You remember the fun of dancing through sprinklers on the lawn!)
  • The cows’ diet changed a little for the day. The cows got a little more grain, a little more green crop and a little less hay yesterday. It takes more energy to digest high-fibre foods, which adds to heat stress. Rather than feeding out the hay during the day, Wayne stayed up late and offered the cows a “night-cap” in the relative cool of the evening.
  • We chose the coolest paddock on the farm, ringed by the deep shade of mature willow trees.
  • On a hot day, dairy cows can slurp up a staggering 250 litres each. Our extra-large troughs ensured they had plenty of fresh, cool water to drink when they chose to emerge from their hideouts.

Poor girls. According to the Cool Cows program leader, Dr Steve Little, dairy cows start to seek out shade when it gets to about 25 degrees C. I think the farm’s cows, dogs and humans all felt the need to go into summer hibernation yesterday.

6 thoughts on “Hot milk

    • Some breeds are certainly more able to deal with summer heat than others. You can have a look at all the different factors on the Cool Cows site. Here’s an excerpt regarding breed:

      “Tropical cattle breeds such as the Brahman tend to be able to cope better than European breeds. They have better heat regulatory capacities than European breeds, due to differences in metabolic rate, food and water consumption, sweating rate, and coat characteristics and colour. As European breeds have a higher heat loading at the skin, they must evaporate substantially more sweat than tropical breeds to maintain normal body temperatures.”
      “Of the European breeds, the Brown Swiss and Jersey are least vulnerable to heat stress, then the Ayrshire and the Guernseys. The Holstein-Freisian is the most vulnerable.”

      Would hate to try to make a living milking Brahmans though!


      • Tellingly, Ian, the site also says this:

        “When feed is consumed and digested, metabolic heat is produced and excess amounts must be unloaded to maintain normal body temperature.”
        “High producers eat more feed and generate more metabolic heat yet must still dissipate their heat load from a similar body surface area as lower producing cows. This makes high-producing herds (and higher producing cows within herds) more susceptible to high environmental heat loads.”


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