As prairie farmers deal with drought conditions this summer, the water quality that cattle consume may also be affected.
Sulfate is a common mineral component that is present at some level in most water sources as well as in many feeds.
However, during a drought, water that may have been acceptable for animal consumption may become toxic as the summer progresses.
Evaporation can lower water levels in dugouts and concentrate mineral levels. The most common form of water toxicity seen in cattle in Western Canada is sulfate toxicity.
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Water that is high in sulfates is not palatable to cattle, but thirst is an even stronger motivator and cattle will eventually drink it. Those that do may show signs of toxicity.
Good guidelines are available for livestock water quality, but a general rule of thumb is that water with less than 1,000 parts per million of sulfate will be acceptable for beef cattle.
Water with sulfate levels between 1,000 and 2,000 p.p.m. may affect animal growth and performance.
Sulfate interacts and binds with copper and makes it unavailable to the animal. This can result in a copper deficiency, which can create low growth rates, impaired fertility, anemia and hair colour changes.
Many areas of the Prairies already have forages that are low in copper, which results in low copper levels in cattle that eat these forages.
Adding water with sulfates greater than 1,000 p.p.m. can easily create a secondary copper deficiency, which will significantly reduce cattle growth and fertility.
Other signs of toxicity appear as sulfate levels in water climb higher. Levels higher than 2,000 p.p.m. may result in signs of nervous disease in the cattle.
Polioencephalomalacia (PEM) is the technical term for a nervous disease of cattle that is characterized by blindness, difficulty walking and seizures. The animals will eventually become recumbent and may die.
Animals with less severe forms of PEM may recover but still have minor neurological symptoms.
The disease was first described in the 1950s and was thought to be caused by a deficiency in thiamine.
Thiamine levels are difficult to determine in cattle, and it has recently been shown that sulfate toxicity can create PEM and is probably the primary cause of the disease.
Consuming water or feed that has exceptionally high levels of sulfate creates hydrogen sulfide gas in the rumen, which is absorbed into the blood stream.
Hydrogen sulfide has a toxic effect primarily on the brain, which results in the many nervous system symptoms of PEM. The development of PEM becomes even more likely if water sulfate reaches 3,000 or 4,000 app.
Ethanol byproducts such as dried distillers grain with solubles have high levels of sulfur, and feedlot cattle that eat these types of feeds and are exposed to moderate levels of sulfates in water may have total sulfur levels that are high enough to create a PEM outbreak.
There is no specific treatment for PEM, and many veterinarians will use thiamine and anti-inflammatory drugs as supportive therapy. Removing animals from water or feed sources that are high in sulfate is absolutely essential.
Water can easily be tested for sulfate levels, and it is important during dry summers to monitor dugouts because their sulfate levels may increase as evaporation occurs.
Your livestock agrologist, veterinarian or nutritionist can help you test your water and interpret the results.
