Water quality testing for livestock

Brad Costin, Agriculture Victoria

Picture of a dam with brown algae slick

Livestock water quality can be affected by a range of environmental factors such as drought, fire and flood. Physical, biological and chemical aspects of livestock water can vary throughout the seasons. Testing of water may be useful to confirm concerns you may have throughout a season.

For example, if stock aren’t performing as expected, if there is evidence of algal blooms, if dams look unpleasant after rain events following fire or drought, or when new bores are being installed.

To get the most out of your water testing, be sure to know why you are testing, what tests you are using and how you will use the results before commencing. It is recommended you use a water testing service that is NATA accredited. Compliance with this standard ensures recognised levels of competence and reliability.

Your water testing service may already have recommended tests for livestock that report on relevant components. Analysis can include many parameters, some are shown in Tables 2 and 3. You can test for individual parameters which could save expense. As there are so many tests, it is useful to focus on what parameters you wish to test for or what the potential problems in the water might be. For example, dams with faecal and other contamination from rain after drought or fire, may have higher than ideal levels of E. coli and other bacteria. Dams that have evidence of algae may only require a test for blue-green algae and toxicity. Bore water is commonly tested for salt and other trace and macro elements.

Salinity tolerances

Table 1 shows the salinity (as EC) and magnesium (Mg) tolerance levels for different classes of stock.

Table 1: Salinity tolerance levels for stock water

Type of Livestock		EC (µS/cm)	Mg/L (ppm)
Beef cattle	Production decline begins¹	6,250	4,000
	Maximum level²	15,600	10,000
Lactating ewes and weaners	Production decline begins¹	6,000	3,800
	Maximum level²	10,000	6,400
Dry mature sheep	Production decline begins¹	9,300	6,000
	Maximum level²	21,800	14,000

1. Production decline begins = upper limit salt concentration for healthy growth.
2. Maximum level = maximum salt concentration that may be safe for limited periods.

Biological tests for microbial pathogens

There are many bacteria that may be of concern to livestock and testing for all risks is not generally feasible. Testing for faecal contamination is used as an indicator and can be reported as total coliforms and/or Escherichia coli (E. coli) in coliform units (cfu/100ml).

The Livestock drinking water guidelines (draft) (2023) provide recommended values for biological, chemical and radiological substances that may occur in livestock drinking water (Table 2). The guideline values are based on the current evidence and literature, with preference given to data from Australia and New Zealand. These values may not be appropriate for all stock types, ages and feeding systems. For example, young or older livestock and non-ruminant species may be more sensitive to some substances. This can make interpretation of results challenging

Table 2: Snapshot of Livestock drinking water guidelines (draft) (2023) recommended values for biological, chemical and radiological substances that may occur in livestock drinking water.’

Substance		Guideline value	Notes
Biological parameters	Cyanobacteria	Toxin-producing cyanobacteria <0.4 mm3/L, (equivalent to 5,000 cells/mL of Microcystis aeruginosa, or 1 µg/L of total microcystins-LR)	Algal blooms should be treated as toxic; remove livestock from the water source until the algae are identified and toxicity is determined
	Pathogens and parasites	<100 cfu/100 mL (median value) of E. coli	E. coli is a critical indicator to manage pathogenic infection risk
Main ions of concern	Calcium	<1,000 mg/L	If dietary phosphorus levels are adequate
	Magnesium	<500 mg/L (ruminants in general) <250 mg/L (lactating cows and ewes with lambs) <125 mg/L (poultry)
	Nitrate and nitrite	<100 mg/L nitrate and <10 mg/L nitrite (livestock in general) <25 mg/L (poultry) <400 mg/L (cattle)	Levels of nitrate tolerance are lowest in poultry, medium in pigs and highest in cattle
	Sulfate	<500 mg/L (livestock in general) <250 mg/L (poultry)	Pigs may tolerate higher levels
	Total dissolved solids (salinity)	<500 mg/L

Note: This is not the entire Table 1.1 as provided in the guidelines.

Testing for blue-green algae (cyanobacteria)

Several tests can be used to quantify blue-green algae and their potential impact, such as taxa present, relative abundance, cell counts, biovolume, toxin presence and genetic analysis. As noted in Table 1, algal blooms should be considered toxic and stock removed until toxicity has been determined.

Not all blue-green algae are toxic, and toxins may or may not be present at the time of testing even for those species that are known to be harmful.

There have been a few toxicological trials carried out to determine safe levels of intake of cyanobacterial cells or toxins for domestic animals, with not all livestock equally susceptible. Species, age and sex can affect susceptibility with monogastric animals less sensitive than ruminants and birds. Careful consideration is therefore required when planning, sampling and responding to bluegreen algae testing results.

Ash and charcoal contamination after fire

The impact of bushfires on water quality is highly variable depending on the timing and intensity of follow-up rainfall, topography and the type and quantity of materials being washed downstream. Charcoal and ash from native forest catchments, grazing land and crop stubbles are relatively harmless to stock being composed of inorganic materials such as calcium carbonate, minerals and trace elements.

Organic materials on the other hand can quickly make water unsuitable for use. These materials rapidly deplete oxygen levels while at the same time release large quantities of nutrients. This can lead to the rapid growth of bacteria, algae and other water borne pathogens.

Consider the impact of bushfires on man-made materials. Highly toxic compounds can be released and washed downstream from a variety of sources including treated timber, stored chemicals and a range of plastic materials.

Water sampling and storage

How and when you take the water sample can affect the result, as well how it is stored before arriving at the lab. Water samples should spend as minimal time in storage and transit as possible. Plan your collection so your sample is not sitting around for days in hot weather. Speak to your lab service about how to coordinate well ahead of time.

When sampling, be clear in your mind about your objective and the water issue you are trying to understand. This should determine your sampling strategy. Do you need a representative sample of the water source where stock are likely to be drinking most frequently? Or is there a problem area where concentrations of biological or chemical constituents warrant specific targeting? Sampling approach can influence results, so careful interpretation is required.

Water quality trial

An on-farm demonstration in the southwest is investigating the impact of water quality on the growth performance of lambs. The main parameters of concern are E. coli, coliforms and other bacteria in several dams on a farm. The lack of clear evidence of the impact of these levels on productivity of stock (in this case growing lambs), is the driver for this on farm trial.

The region has experienced 2 very dry years. Two dams were tested last year, and one had high levels of E. coli, coliforms and other bacteria (Table 3). High E. coli levels are considered to be a strong indicator of faecal contamination.

Table 3: Pathogen tests results for 2 dams tested in 2025

Dam	E. coli	Coliforms	Other bacteria
A1	2,000	2,000	290,000
A2	210	400	145,000

The results for dams A1 and A2 showed high levels of pathogens in 2025, noting that details on water sampling and storage before testing are unknown.

As noted above, water quality can change from season to season and year to year. The results from this year (late February) for the 2 dams A1 and A2, plus tank water from a shed roof and an additional dam on the farm are shown in Table 4. E. coli, coliforms and other bacteria levels for A2 and A3 are considerably lower than last year. Notably, samples collected in 2026 were stored under refrigeration and transported to the laboratory in an esky, as light exposure and higher temperatures can cause bacterial counts to increase.

Table 4: Pathogen results for 3 dams (A1, A2, A3) and rainwater (collected from a shed roof in a tank) tested in 2026

Water source	E. coli	Coli- forms	Other Bacteria	pH	EC uS/cm	TDS ppm salt
tank	4	25	800	5.5	53	33
A1	160	180	63000	7.3	432	270
A2	80	70	14000	8.6	1220	759
A3	40	100	120 000	8.5	1530	955

A pH above 9 could potentially increase the availability of toxic elements, but it is not clear if this is significant in this case. The trial will compare the performance (as growth rate) of lambs drinking water from these sources compared to rainwater and treated dam water.

Results of the trial will be in the spring edition of SheepNotes.

Note: Keep in mind your own safety when sampling, including the use of gloves when sampling algae blooms.

References

Page last updated: 15 May 2026