Supplying Water to Rotationally Grazed Beef Cattle

6 June 2024

Designing an effective rotational grazing system involves ensuring a reliable supply of clean drinking water for livestock across multiple paddocks or pastures. This system must withstand weather extremes and ensure continuous access to water, as lack of access can cause stress and impact animal performance.

A 700 kg lactating cow can drink 105 litres of water daily, compared to the human guidance of 3-4 litres per day, livestock require significant amounts of water and we should design systems that deliver peak amounts of water.

This article will:

Take you through the fundamentals of sourcing water
Outline how to calculate your water requirements
Advise on how to set up an effective water infrastructure on your farm
Review the advantages and disadvantages of fixed vs mobile troughs

Choosing Your Water Source

Most UK farms (around 85%) have a mains water supply, with 31% also abstracting from watercourses and around 25% using boreholes (Source: AHDB). The ideal water supply system is gravity-fed from an uphill source ensuring pipes do not leak, maintaining sufficient pressure to the troughs. Height translates to pressure; 10 metres of head above target destination = 1 Bar of pressure (14 psi). Pumping water to a header tank is an option for those not fortunate enough to have a natural source uphill, this also provides a buffer.

Investing in a borehole may be more economical long-term than using mains water.

Types of Water Pump

The pump must deliver the required flow rate considering total pressure, including elevation change, pipe friction loss, and valve operating pressure.

Electric or fuel-based pumps are reliable but expensive to run. Solar-powered pumps work well but are less effective in low-light conditions, this can be buffered with a larger header tank.

A RAM pump utilises the water hammer effect to generate pressure, enabling a portion of the input water to be elevated to a point higher than its original source. This makes the RAM pump ideal for situations where water must be pumped to a higher elevation than the source.

Picture Credit: Clem Sandison

Water Legislation in Scotland

If you choose to invest in a borehole, make sure you’re aware of the abstraction licensing regulations which apply to those using natural water sources. If abstracting up to 10 cubic metres of water per day, compliance with General Binding Rules grants authorisation. For 10 to 50 cubic metres per day, a one-off registration with SEPA is required. Higher volumes need a “simple” licence with an annual fee. Consult your local farm consultant or SEPA office for more information.

How to Calculate Your Livestock's Water Demand

Water demand varies with temperature, grass dry matter, and whether the animals are lactating. Estimate water needs using the following calculation:

Animal Live Weight (kg) x 12% (Dry Stock) or 15% (Lactating) = litres/day.

For example, a 700 kg lactating cow requires 105 litres per day.

Consider Peak Water Consumption When Calculating Flow Rate

Consumption depends on access to supply. Cattle are more likely to drink as a herd when the trough-to-grazing allocation ratio is less than 0.5 (one trough to 2 hectares) or if deprived of water for more than two hours. One cow can consume up to 14 litres per minute, creating high peak demand.

If a cow requires 104 litres of water per day at peak demand, a herd of 40 cows require 4,200 litres per day. If this was consumed evenly throughout a 24 hour period, the system would need to supply water at a flow rate of 2.9 l/minute (4200l ¸ 1440 minutes in 24 hours). However, they do not drink evenly throughout the day and they often drink as a herd. To be prepared, the supply system should pump the required daily water within four hours.

Therefore, 40 cows requiring 4,200 litres per day, the flow rate needs to be 17.5 litres per minute.

If the trough-to-grazing allocation ratio is greater than 0.5 (one trough to 2 hectares), cows will drink individually. For calculations, assume consumption over a 5-hour period:

For example, if 40 cows require 4,200 litres per day or 840 l per hour or 14 litres per minute.

Selecting an Appropriate Pipe Size for Your Needs

A common problem in water infrastructure is the use of pipe sizes too small which adds friction and therefore reduces the water flow rate.

Pressure drop in water pipes is influenced by pipe length, pipe diameter, water flow rate, and elevation change (10 meters up/down equate to 1 Bar of pressure (14 psi) lost or gained). The net effect of pressure loss is reduced flow rates. Increasing system pressure to maintain flow rate is not a good solution; it is energy-inefficient – better to design the system to deliver the flow rate required.

Table 1 Pressure loss in psi for different pipe sizes at various flow rates for 100 metres length of water pipe (Taken from Teagasc Beef Farm Programme Infrastructure Handbook)

	Flow rate m³ per hour (litres per minute)
Pipe diameter (mm)	1 (17)	2 (33)	3 (50)	4 (67)	5 (83)
20	14.2
25	3.27	11.5
32	0.64	2.27	4.83	7.6	11.65
38	0.34	1.21	2.49	4.05	6.25
50	0.11	0.38	0.88	1.34	2.06

Pressure loss and reduced flow rate are directly proportional to pipe length; doubling the pipe length doubles the pressure loss. Use Table 1 to determine the pumping pressure lost for various pipe sizes and flow rates, considering pipe length.

Fixed vs. Mobile Troughs

When choosing waterer sites, select locations that are high and well-drained. For paddock grazing, it is good when you can locate the trough to serve multiple paddocks, this can be in the middle of a field or at gateways where the fence can be aligned at either side of the trough.

Fixed Troughs	Mobile Troughs
+ Easy	+ Flexibility to move with stock, suitable for infinite paddocks
+ Buffer for low-flow	+ Reduced ground impact
+ Frost protection	+ Reduced investment
- Risk of poaching	- Require minimal flow rate
- Higher initial cost	- Not suitable for direct mains water supply (need an air gap in the system)
- Fixed position