Water – can all your cows get enough?

Published 18 July 14

As most of the country is experiencing warm to hot temperatures, and the long range forecast predicting more to come, Piers Badnell, AHDB Dairy Technical Extension Officer, asks if your cows are getting enough water. Because a lack of is water not only a welfare issue, it is also a profit issue.

A few years ago, an AHDB Dairy Discussion Group examined the water trough positioning in a field. The host had reasonably sized troughs in each field, but they were tight up against the hedge, so only half available to the cows. It was suggested to move them into the centre of the paddock, to allow good access for all the cows. The response was: “What about silaging? Troughs will be in the way, and the pipe gets cut while mowing.” To which the group replied: “You sell milk, of which the main component is water, so why would you restrict water?” Followed by, “Get a better tractor driver!” Lastly, a group member explained he moved his troughs from the hedge to the centre, and yield went up by two litres per cow over night!

At an AHDB Dairy Discussion Group last Tuesday (15 July), we measured flow rate of water into a trough, using a target of 14 litres per cow per hour. The flow needed to be just over 1,000 litres, it was 700 litres. It’s a very crude but a useful exercise, and is done by holding a jug under the inlet and timing how long it takes to fill.

Cows like to do things together and will all troop off to the trough for a drink. They also have a pecking order, meaning the top ‘boss cows’ get all they need. But do the low order cows or heifers get enough? I once watched a heifer in a large grass-based herd walk towards the water trough. At a distance of about 15m she stopped, looked at the cows around the trough and did not proceed. You could see she wanted to but she was not brave enough to ‘push in’.

She then saw another trough without cows and set off towards it, only to realise it was in the next paddock and an electric wire was in her way. Did she get enough to drink that day? I don’t know but that was a cold day in March, with reasonably low dry matter grass and a good-sized water trough in the paddock with good flow rate. It wasn’t 25°C, with a too small trough and poor flow rate.

How do we get enough water to the cow?

We get enough water to the cow through a combination of trough sighting, volume and flow rate.

  • Make sure the trough is accessible from all angles
  • If the trough is under a fence line, make sure it can be moved so cows can get all the way round. Certainly, do not let the fence touch the trough or make it too low so that when she puts her head into drink gets a shock. I have seen this on farm!
  • Make sure the trough is big enough or have another trough
  • Make sure the flow rate is adequate
  • Water requirements depend on dry matter percentace of feed, animal production stage of lactation and temperature

How do you calculate a cow’s requirement? One way is to calculate that a cow needs 30-40 litres for her maintenance, plus 3-4 litres per litre produced. This is in temperatures up to 20°C, and requirements rise with the temperature.

Drinking water requirement will be in the region of 70-80 litres per day but, on a hot day, it can rise to 140 litres. For example, in a five-hour period during the day, on a hot day, the cow requires 70 litres of water, which equates to 14 litres an hour.

As an example: 150 cows at 14l/hr = 2,100 litres/hour flow rate, which is needed. This is the same as 35 litres per minute. Get a jug and measure if your flow rate can keep up.

A good check is that the trough should hold half the one hour demand. So, for our example above the trough should be able to hold 1,050 litres.

Other considerations for improving water availability are:

  • Will your herd increase in the future – factor this in
  • Check legal requirements – usually referring to non-return valves
  • Water is expensive have you thought of a borehole?

More information about water supply can be found in Factsheet 4 “Water at Pasture” of AHDB Dairy’s Grass+, Chapter 11 “Water provision” of the Dairy housing a guide to best practice, in the “Effective use of water on a dairy farm” booklet and in the article “Water provision”.