Water quality for livestock

Livestock owners should consider water quality when planning and reviewing the water supplies for their livestock. If water quality is poor, livestock may drink less than they need or, rarely, may stop drinking altogether. When animals drink less, they will eat less and lose condition and if they are lactating, their milk production will reduce or cease.

Important water quality issues for livestock include water salinity and the presence of water contaminants such as blue-green algae, organic material, heavy metals and chemicals.

Water salinity

Water salinity is the sum of all the salt ions dissolved in water, including sodium, calcium, magnesium, chloride, sulphate and carbonate. Water salinity is generally the most important water quality limitation for livestock as they can refuse to drink excessively saline water leading to loss of production. Excessively saline water may cause salt poisoning in livestock.

Salinity is usually determined by measuring the electrical conductivity of the water. The commonly used units of electrical conductivity are milliSiemens per metre (mS/m). Less commonly, conductivity may be expressed as milligrams/litre (mg/L), which is approximately the same as parts per million (ppm).

Total dissolved solids (TDS) is the sum of all the ions dissolved in water plus dissolved organic acid molecules. Because salts usually dominate, salinity and TDS are usually highly correlated, however organic acids may contribute to the conductivity reading in water with a high organic content. These days it is more common and practical to measure conductivity, rather than TDS.

Tolerance to saline water varies between livestock species (see Table 1). Pregnant, lactating and younger classes of livestock are less tolerant than mature dry stock. For optimum production in these classes of livestock, water supplies should not exceed the salinity levels towards the lower limits of category B in Table 1. Livestock grazing green feed can better tolerate salinity levels at the upper limit of each category compared with those grazing dry feed or salt bush or on a high salt diet, as the high water content of green feed will dilute the salinity levels of the water supply.

Table 1 Approximate tolerances of livestock to dissolved salts (salinity) in drinking water (conductivity in mS/m). Adapted from Australian and New Zealand Guidelines for Fresh and Marine Water Quality (2000) and (1992).
Livestock

A

No adverse effects on animals expected

(mS/m)

B

Livestock may have Initial reluctance to drink or may scour, but should adapt without production loss (mS/m)

C

Loss of production & decline in animal health/condition expected. Livestock may tolerate these levels for short periods if introduced gradually (mS/m)

Beef cattle

0–730

730–900

900–1800

Dairy cattle

0–450

450–730

730–1270

Dairy cattle (milking)

   

640

Sheep

0–730

730–1800

1800–2360

Sheep (weaners, lactating & pregnant)

   

1100

Horses

0–730

730–1100

1100–1270

Pigs

0–360

550

730

Poultry

0–360

360–550

550–730

Note: To convert conductivity in mS/m to TDS in mg/L or ppm, multiply by 5.5. The factor 5.5 provides a better approximation in water in Western Australia.

Sheep on lush green feed may tolerate up to 2360mS/m (13,000mg/L TDS) without loss of condition or production.

Salinity of a water supply can change over time and between seasons. Salinity levels of dams, creeks, soaks and waterholes should be checked during summer as salinity often increases during summer due to evaporation. Salinity levels can be kept as low as possible by cleaning tanks before each summer and scrubbing and flushing water troughs frequently, even up to twice a week.

Stream salinity can increase after the first rains as salts left on dry creek beds over summer are flushed downstream. Long-term increases in water salinity are usually associated with land clearing and rising watertables leading to more salt seeping into water supplies. Groundwater is usually more saline than surface water.

While TDS and salinity provide a guide to water quality, the concentration of calcium, magnesium, nitrate/nitrite and sulphate ions may also need monitoring especially if using groundwater as they can cause purgative or toxic effects. For example, while magnesium is essential in animal nutrition, it may cause scours and decreased production at high levels, so when TDS exceeds 3,000mg/L, it may be advantageous to know the concentration of magnesium.

Water testing for salinity is available in most regional towns, chemistry laboratories and from the Department of Agriculture and Food, Western Australia (DAFWA) Diagnostic Laboratory Services (DDLS) at South Perth. See water testing section below.

Blue-green algae

Blue-green algae are a group of algae including Nodularia spumigena, Microcystis aeruginosa and Anabaena circinalis. They can produce spectacular blooms appearing like iridescent green paint or curdled greenish milk on water surfaces.

Algae multiply rapidly (‘bloom’) in shallow, still warm water when the water is contaminated by plant nutrients including organic and faecal matter and phosphorus.

Livestock can be poisoned by drinking water contaminated with blue-green algae and their toxins. Read more on blue-green algae.

Contamination with debris or animals

Water can become contaminated by birds, animal droppings, animal carcasses or run-off from bare paddocks, intensive livestock industries or sewerage waste. This can result in low production, disease or deaths in livestock. Botulism and salmonellosis are two livestock diseases that may result from contamination of water with organic matter. Read more on botulism in cattle and salmonellosis of sheep.

Mats of organic matter should be removed from water by skimming the surface within 48 hours to prevent sinking. Water polluted with organic material can be treated with chlorine, although chlorination does not kill all disease-causing bacteria and does not affect toxins already present in the water. Chlorination is not suitable for farm dams.

Contamination with heavy metals or chemicals

Water can contain elements and compounds which, at elevated concentrations, can cause toxic effects or residue issues. Heavy metals, such as arsenic, lead, mercury, selenium, zinc and the fluorides, and pesticides are of particular concern. While high concentrations of some heavy metals can be found in groundwater, sources of these metals and pesticides are generally run-off, seepage or spillage from arable land and industrial or sewerage waste. If there is a high contamination risk or where productivity losses are suspected, a detailed water analysis should be conducted.

Never use containers that have been used for herbicides, pesticides or fertilisers for carting water for stock. Deaths have occurred in livestock due to water contaminated with nitrogenous compounds from fertiliser containers. There is also a risk that livestock could develop chemical residues in their tissues which, if detected, could result in serious trade consequences.

Miscellaneous stock water issues

  • Cloudy or muddy water can be a nuisance in water for domestic use and may block irrigation spray nozzles, but it rarely harms livestock.
  • Large paddocks: When feed is dry and paddocks are large (greater than 100 hectares), two watering points or a moveable trough will allow better use of the entire paddock, reduce localised erosion risk and allow better animal performance.
  • Warm water: Stock avoid warm water in hot weather, so deeper or shaded water sources will generally be preferred. Pipes carrying water above ground may deliver very hot undrinkable water to troughs.
  • Lupin stubbles and weaner sheep: In summer and autumn, weaner sheep on lupin stubbles (and possibly other high protein diets) will not travel more than 500–600 metres from a water source. This increases the risks of soil erosion and lupinosis from grazing continuously around the water point.
  • Large mobs on troughs: With large mobs of sheep (more than 600), the tail of the mob may not drink enough water before the sheep move away. The flow rate in troughs needs to be sufficient to keep water in the trough while all sheep drink. Allow at least one metre of trough per 130 sheep.
  • Finding water, recognising troughs: Sheep not used to water troughs may take time to learn to drink from them. Young sheep are less adept at finding water so always push them onto water in a new paddock.
  • Dams versus troughs: Many producers observe that weaner sheep do better in summer-autumn on dams rather than troughs. This could be because of the previous two issues.

Contact information

Roy Butler
+61 (0)8 9081 3110
Page last updated: Thursday, 2 February 2017 - 5:51pm