"Drought makes it imperative for producers to monitor the quality of water their livestock are drinking," say South Dakota State University (SDSU) specialists.

Using South Dakota as an example, Cody Wright, SDSU beef specialist, explains, "Water from stock dams, streams and wells is often high in total dissolved solids (TDS), and especially sulfates."

Drought makes the situation worse because salt concentrations increase from enhanced evaporation and diminished moisture recharge. In addition, SDSU researchers note drought conditions sometimes force producers to use water of marginal quality if no other water is available. Animals will voluntarily consume less poor-quality water, and eat less feed/forage as a result.

Russ Daly, SDSU Extension DVM, adds that livestock may experience increasingly serious health and production problems as water quality declines.

More specifically, in South Dakota -- where it appears sulfates are the salt that causes most problems -- Daly explains high sulfate intake may cause health problems in ruminants. The most notable of these problems is sulfur-induced polioencephalomalacia (PEM). Symptoms of sulfur-induced PEM include lethargy, anorexia, blindness, muscle tremor, exaggerated response to sound or touch, and a lack of coordination, which progresses to staggering, weakness; eventually it leads to convulsions and inability to get up.

Recent research suggests sulfur-induced PEM may be different than another type of PEM caused by a thiamin (Vitamin B1) deficiency. In the case of sulfur-induced PEM, supplemental thiamin has produced mixed results.

According to SDSU researchers, the level of sulfur intake that's problematic varies by the type of diet the cattle are consuming. Sulfur intakes below 0.3% of diet dry matter (including contribution of water) are safe for all classes of cattle. Levels above 0.3% can be associated with sporadic cases of polio in cattle on high-grain diets. Cattle consuming forage-based diets can consume as much as 0.5% safely. Intakes of greater than 0.7% may be associated with a significant number of cases, regardless of diet.

If producers continue using water with high sulfates, SDSU specialists said there are steps they can take to help lessen the risk to livestock.

When situations dictate the continued use of water with high sulfates, SDSU specialists said these steps can help lessen the risk:

• Check livestock frequently, minimize other sources of sulfur/sulfates in the diet.
  
• Monitor water quality at regular intervals.
  
• Do what is possible to minimize heat stress.
  
• Work with a veterinarian to develop a protocol for treating acute cases of sulfur-induced PEM, as animals often die from the disease if not treated promptly.
  
• Consider alternative water or blending "good" and "bad" water, especially in very hot weather.
  
• Producers who have multiple water sources should test all sources and formulate a water-use strategy. Use marginal water first, saving good-quality water for later in the summer, since water quality will likely decline over the summer.