Testing your stock water is critical in dry seasons
Good quality water is extremely important for stock health. The major water quality problem during dry periods is high levels of salt. There is also potential for algae and animal manures to foul water following heavy summer rains or strong winds.
Water quality will determine what farm water may be used for. Poor water quality has the potential to affect not only livestock health but also:
- plant growth
- soil quality
- farm equipment and infrastructure
- domestic use.
Cool and clean water with a low salt content is best for stock health and for household use.
Other minerals in water can also affect livestock health. Table 4 lists the upper limits of minerals and metals, and their effect on animal health.
During a dry year, low water levels in dams from evaporation can result in doubling of the salt concentration over the summer. Stock will drink more water as salt levels increase.
Table 3 shows the salt levels at which production declines for various types of livestock. In general, the salt content should not exceed 5000 EC (electrical conductivity units) for young stock, 6000 EC for mature cattle and 9000 EC for mature sheep. However, stock can tolerate higher levels of salt for short periods.
Table 3. Salinity levels for stock water above which production declines
| Type of livestock | Salt concentration EC (S/cm) | Salt concentration mg/L (ppm) |
|---|---|---|
Mature sheep | 9300 | 6000 |
Nursing ewes | 6000 | 3800 |
Lambs | 6000 | 3800 |
Mature cattle | 6250 | 4000 |
Lactating cattle | 5000 | 3200 |
Calves | 5000 | 3200 |
Table 4. Water quality stock tolerance levels
| Element | Rainwater | Upper limit | Effect |
|---|---|---|---|
Calcium | 40mg/L | greater than 1000mg/L | Phosphorus deficiency |
Magnesium | 0 to 19mg/L | greater than 1000mg/L | Scouring and diarrhoea |
Nitrate | 10mg/L nitrate, 1mg/L nitrite | greater than 1500mg/L nitrate, | Vomiting, convulsions, death |
Sulfate | 250mg/L | greater than 1000 to 2000mg/L | Diarrhoea |
Aluminium | 0.05 to 0.2mg/L | 5mg/L | Phosphorus deficiency |
Arsenic | 0 | 0.5mg/L | Diarrhoea, anaemia, poor coordination |
Copper | 1mg/L | 0.5mg/L | Liver damage and jaundice, copper accumulation in liver |
Fluoride | 1mg/L | greater than 2mg/L | Tooth damage, bone lesions |
Iron | 0.3mg/L | None (low toxicity) | None |
Lead | 0.015mg/L | 0.1mg/L | Respiratory diseases, anorexia, uncoordination |
Molybdenum | 0 | 0.15mg/L | Scouring, loss of condition, infertility, skeletal disorders, testicular damage |
pH | 6.5 to 8.5 | greater than 9, less than 5 | Other minerals become available, such as copper and aluminium |
Total dissolved solids | 500mg/L | Variable — generally greater than 5000mg/L | Poor production, diarrhoea, higher mortality rates |
Mineral and metal levels will vary as a result of specific geology, weathering, acid conditions, high salinity levels and management. If feed contains the particular minerals, limits are lower. Guidelines are from Australian and New Zealand Environment and Conservation Council and Agriculture and Resource Management Council of Australia and New Zealand (2000). Australian and New Zealand guidelines for fresh and marine water quality, ANZECC and ARMCANZ, Canberra.
To conserve water and maintain good water quality, one large, deep dam is better than several shallow dams. Research has shown that animals that drink from regularly cleaned troughs perform better than those that drink directly from dams.
During dry conditions, dam water can be polluted by manure and dried vegetation blowing from bare paddocks, causing dirty and smelly water that stock find unpalatable. This material should be removed promptly. Maintaining groundcover on paddocks adjacent to dams will avoid the problem.
Algal blooms are common during summer months when water temperatures rise as dam levels fall, and the levels of phosphorus and nitrogen in the water build up. Most algal blooms are not toxic. However, some blue–green algae produce toxins that can have serious health implications for animals and humans. These toxins can kill animals within a few hours of ingestion. If blue–green algae are suspected, animals should be isolated from the dam water, and a sample should be collected for testing by a water laboratory.
The best way to be certain about the quality of your water is to have it tested. Water should be monitored and tested for salinity regularly, and monthly during summer or drought.
Water samples can be tested at home using salinity (EC) meters. Portable EC meters are relatively inexpensive and available at water equipment dealers. Samples can also be tested for salt content for free at a number of department offices. Phone the Customer Service Centre on 136 186.
For more information, contact Greg Bekker on 0417 340 236 or
greg.bekker@agriculture.vic.gov.au