Sulfate salts present a major problem for water quality in large parts of North America, particularly for range cattle. In the semi-arid climates where the majority of beef cattle are grazed, hot, dry summers contribute to sulfate problems through evaporation of surface waters. This leads to increasing sulfate concentrations as the summer progresses.



A white salt or "alkali" ring around the edge typically identifies ponds and dugouts containing high levels of sulfates, particularly later in the summer months when much of the standing water has evaporated. Mineral analysis of water samples in a laboratory can then be used to determine the actual sulfate salt concentration.



At high levels, sulfate salts can cause cattle to reduce their water consumption. When this happens, feed intake and feed efficiency are generally reduced and average daily weight gains are lowered. If water quality is very poor, cattle can suffer from dehydration. Sulfates also contribute to the development of polioencephalomalacia (polio), a metabolic disorder that can reduce productivity and result in death.



Not all sulfate salts are alike. Depending on local conditions, water high in sulfate may be mainly sodium sulfate (Na

2

SO

4

; "Glauber salt"), magnesium sulfate (MgSO

4

; "Epsom salt"), or a combination of these and less prevalent salts.



Recent research conducted at the Agriculture and Agri-Food Range Research Unit in Kamloops, British Columbia, in conjunction with the University of British Columbia Animal Welfare Program, has shown that cattle respond differently to different sulfate salts. In a series of experiments, sodium sulfate and magnesium sulfate were tested for their effect on water consumption and animal health.



Yearling heifers and steers were group-housed in pens and provided water individually using electronic head gates. Cattle were exposed to either tap water or water containing sodium sulfate or magnesium sulfate for between 2 and 21 days at sulfate concentrations ranging from 500 to 4,500 parts per million (ppm). Individual water consumption and fecal dry matter were monitored.



When the water contained more than 3,000 ppm sulfate, cattle reduced their consumption. However, the response was stronger to magnesium sulfate than to sodium sulfate. With magnesium sulfate, as sulfate concentration increased, average daily water consumption dropped from about 40 liters (10.6 gals.) per day to only 13 liters (3.4 gals.) per day at 4,500 ppm sulfate. With sodium sulfate, the reduction wasn't as drastic. During the experiments some cattle objected so strongly to water containing 3,000 and 4,500 ppm sulfate that they didn't drink for two days.



After 21 days of drinking water containing 4,000 ppm sulfate as magnesium sulfate, cattle feces were significantly drier than when the same animals were drinking tap water. This suggests the animals were starting to become dehydrated. Over time, this low water consumption is likely to lead to reductions in feed intake and productivity.



Some final thoughts. Sulfate salts detract from the quality of a water source. They become a clear problem at concentrations of 3,000 ppm and above, and more so if magnesium sulfate is the predominant salt.



If producers are faced with high sulfate levels, they should closely monitor their cattle for reduced productivity or signs of illness such as polioencephalomalacia. Producers may be able to address this problem by moving their cattle to alternative sites, as good quality water is sometimes available in ponds and dugouts located near poor quality water. Running water is generally lower in sulfates and could be pumped to troughs. Alternatively, water may be brought in from outside sources.



David Fraser is a professor at the University of British Columbia's Animal Welfare program. Amanda Grout recently completed her M.Sc. and is a research assistant with the same program. Contact her at amandaz@interchange.ubc.ca.