Dean Revell (CEO - BSc (Agric) PhD)
Air temperature, water consumption and feed intake are all related. Change any one of these things and it will affect another. We can’t control ambient temperature, other than allowing livestock access to shaded areas, but we can do something about water consumption and feed intake. We’ll talk about ways to influence feed intake of range cattle or sheep in a later article. Here we’ll focus on water consumption.
Water is often considered the most essential nutrient. I normally don’t think of water as a nutrient, but we could. Like any nutrient, a deficiency in consumption affects performance. Animals need more water when it gets hot because it is essential for their main way of cooling – sweating and panting. Sweating and panting work like an evaporative air conditioner. Heat is released from the body in blood vessels in the skin (with sweating) or the lungs (with panting). Heat is lost by evaporative cooling on the moist surfaces on the skin, tongue or nasal passage. Like an evaporative cooler in a house, it only cools with air movement, and you need water to be running through the system. If animals can’t release the build-up of heat in their body, they will reduce feed intake. And they get hit with a double whammy with more energy spent on panting and less energy consumed.
So access to cool clean drinking water is important.
At air temperatures less than 25°C, water requirements range from about 4 to 8 litres water/kg dry matter (DM) intake for cattle, and 2 to 6 litres water/kg DM intake for sheep and goats. At higher temperatures, water intake per unit of feed intake can at easily double (values of 16 litres/kg DM intake reported with Bos taurus cattle at 38°C).
To put this into context, let’s use the rule of thumb of sheep eating about 1 kg DM per day and cattle 10 kg DM per day (but of course it depends on body weight and feed quality). Sheep will eed about 5 litres per day and cattle 40 litres a day. We can add another litre per day for sheep and another 10 litres per day for cattle for every rise of 5°C in the air temperature. It doesn’t take much to double the amount of water required by an animal each day.
The other thing that adds to the need to drink water is salty feed. If the animals are grazing bluebushes or saltbushes, or other forages on salt lakes such as samphire, the extra salt consumed stimulates more drinking. More drinking dilutes the salts in the body and helps the kidneys get rid of excess salt. Salty forages can double water consumption too – so imagine the combined effect of salty forage and hot days. What can make thing tricky for animals is salty forage, hot days and salty drinking water. The drive to drink more because of salty food (that’s why the pub serves salted peanuts and chips… because it makes us drink more!) and heat is compromised if the water is brackish.
So what can you do about it? A few things:
- As much as possible, provide fresh and cool water, and maybe even consider piping good quality water to certain areas if the local groundwater is brackish. Of course, the practicalities and cost don’t make this easy.
- Try to ensure that through good grazing management your livestock have a range of plants to graze, so they aren’t forced to eat only salty forages. Of course, the realities of drought conditions don’t always make this easy either.
- In the longer term, think about the placement of new water points in relation to grazing areas and water quality. Near saline areas, more accessible drinking water (i.e. shorter grazing radius from water points) might be helpful.
We saw an excellent but simple set up to shade water in troughs at Weebo Station, near Leinster in WA. Bryan and Shannon have built very effective, permanent shade over each of their troughs, as shown in the photo. Their troughs are all aligned either north-south or east-west, and they have found the shade is more effective with east-west alignment.
While supplying cool water for drinking doesn’t directly cool animals (because the biggest cooling effect is by evaporative cooling as described above), research has shown that benefits associated with drinking cooler water have a significant impact in reducing heat stress. Guidelines for lot-fed cattle, which is still useful for rangeland animals as their physiology is the same even if their intake and rates of weight gain differ, is that drinking water should be supplied at about 16-18°C and not above 25°C. Unshaded water on stations will get well above 25°C in summer, and a simple shade structure will be beneficial.
Perhaps the clincher for Bryan and Shannon is that shading the water has significantly reduced the amount of algae growing in the troughs and reduced the time spent cleaning troughs on mill runs.
We think it’s a great example of bush science in action.
Above: shade structure over water trough on Weebo Station in WA