Check your cattle water sources for nitrates this summer

Russ Daly
Whether water comes to animals through a fountain, stock tank or pond, we often take its quality for granted.

It’s the most important nutrient, whether you’re a cow, a dog or a person — yet, I’d venture to guess it’s the one taken most for granted.

It’s not protein, vitamins, nor carbohydrates – it’s water. 

Most people have heard the adage that animals (people, too) can survive for weeks without food, but only days without water. Thankfully, complete lack of water is a rare occurrence with livestock and usually due to equipment failure or an inadvertent shut-off to a barn or lot.   

Whether water comes to animals through a fountain, stock tank or pond, we often take its quality for granted.  While people seem to have gotten pickier about their drinking water (bottled water being popular now), that hasn’t always translated to our animals.  After all, we see cattle drinking out of some pretty nasty-looking places and still doing OK.  We wouldn’t dip a drink out of muddy sloughs or stock dams, but cattle do it all the time. 

Yes, most animals seem to get by sufficiently with water we wouldn’t drink. Livestock species differ in their sensitivity to poor water quality, with poultry more sensitive and perhaps horses and pigs less sensitive, due to their simple stomachs and lack of rumen bacteria.  Within species, younger animals, pregnant animals and lactating animals depend on higher-quality water than others. 

Dry weather conditions can create some real problems for water quality in our pastures and lots.  Rural or well water sources are usually shielded from these conditions, but the quality of surface water in stock dams or dugouts really depends upon their replenishment with fresh runoff from rains.  Without that replenishment, dry hot conditions work to concentrate salts in the water.  When diluted out with enough fresh water, these compounds don’t present problems.  Stale water that hasn’t been recharged, or has taken on runoff from highly fertilized fields nearby, is subject to those problems. 

Already this year we have encountered cow death losses on pasture due to poor, or toxic water quality. Multiple animals faced with drinking out of a single problematic water source have fallen victim to sudden deaths. In many cases, the water itself does not appear all that bad when observed with the naked eye. But high levels of certain salts can kill animals that drink enough of the affected water. 

Water analyzed in these cases has been high in sulfates and nitrates. Either one can kill animals, especially ruminants. High sulfates, especially when combined with high levels of sulfur in other feedstuffs, are more likely to cause non-fatal production problems rather than mortality, but they can cause fatal cases of polio in calves and cows alike. 

Nitrates can kill animals quickly. When high levels are consumed, they interfere with the blood’s ability to carry oxygen to the cells, and the animals die from a sort of internal suffocation.  This chemical reaction doesn’t occur as profoundly in simple-stomached animals such as horses and pigs; cattle are much more sensitive to the effects of nitrates. 

Another potential cause of lethal nitrate levels in drinking water occurs when water is hauled in tanks that previously held nitrogen-containing fertilizer. Even when tanks are supposedly “clean,” it only takes a small residue to create a poisonous condition. 

Sulfates and nitrates are present in water in the form of different salts; other salts can be also be problematic in water.  Their total levels in a water sample can be determined by a simple test for Total Dissolved Solids (“TDS”; sometimes also referred to as electrical conductivity or “EC”).  Total Dissolved Solids levels of over 7,000 are considered risky, and considered toxic if over 10,000.  One recent sample from a pasture experiencing cow death losses was over 14,000.  Arranging alternate water sources isn’t convenient, but neither is losing cows. 

Many state Extension centers as well as many county offices are equipped to test water samples for TDS.  It’s a quick way to determine whether a water source is generally safe or not.  Further testing at outside labs could then be performed to determine which salts (nitrates, sulfates) are problematic. 

Recent cattle death loss problems have occurred after cattle were moved to a new pasture and new water source.  Especially this year, producers should check their stock dams and dugouts before moving cattle onto those pastures.  Contact your local Extension office or veterinarian for information on how to get water samples checked. 

It’s an extra step, but an essential one this year. 

Russ Daly

Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University.