Water Quality in Times of Drought
During times of drought, water quantity is an obvious concern to livestock producers. Livestock consume water daily, but evaporation is the primary means of water loss from earthen impoundments. Evaporation rates increase with the temperatures, but are greatly dependent upon the characteristics of the water body. As water levels within impoundments decrease and water temperatures increase, water quality for livestock (and wildlife, horses, pets and humans) becomes an increasing concern. Therefore, testing water quality can be an important step as water levels shrink. Following are some issues often encountered when water quantity and quality become limited.
Total dissolved solids (TDS), nitrates, sulfates
Increased concentrations of total dissolved solids (TDS) can cause palatability and toxicity problems. If TDS exceed 7,000 ppm, immediately provide a better water source to the herd. Additionally, nitrate and sulfate levels in the water and feedstuffs must be known so that their total intake can be calculated. Unless taken into account, the cumulative effect of nitrate intake from both water and forage can cause large-scale problems in your herd.
Water quality for livestock consumption is a concern during drought. However, the incidence of dangerous algal and bacterial blooms can be reduced by preventing cattle from wading and loafing in ponds.
Algal and bacterial blooms
During periods of excessive heat, cattle can be observed loafing in ponds more frequently. When livestock are able to wade and loaf in ponds, their manure, urine and disturbance of pond sediments increase the nutrient load in the water, which in turn promotes algal and bacterial blooms. These blooms can reduce water quality and intake, as well as produce moderate to severe toxicity. Preventing cattle from loafing in a pond can help extend water quality and quantity. One way to limit livestock access to pond water is by fencing out most of a pond and constructing a water access point (see the Ag News and Views article Pond Fencing).
While most algal and bacterial blooms are not toxic, it is nearly impossible to identify poisonous species without a laboratory analysis of a sample. Cyanobacteria (also called blue-green algae) can produce neurotoxins and cause liver damage. The effects of animals (or humans) suffering from neurotoxins include weakness, difficulty breathing, staggering, convulsions and possible death. Liver damage in an animal is often less acute, taking days to occur, and may only be identified by a postmortem exam. These bacteria get their energy from the sun. As they store the energy, they create tiny pockets of air. Cyanobacteria regulate their volume/amount of air to move up and down in the water (like a small submarine) to find nutrients. The bacteria themselves are not a concern. The issue occurs when some species release toxins that can be potentially lethal to livestock. This is particularly a problem during drought conditions as temperatures rise and water levels become low. A potential danger sign of cyanobacteria toxicity can be the presence of dead fish, turtles or small mammals on the downwind side of a pond.
Pond water can be tested to determine whether it is of sufficient quality for livestock consumption; however, the water test is only a snapshot of the day when it was collected. By the time test results are known, water quality could change significantly. The take home message is to constantly monitor your pond water quality, especially as quantity becomes more limited, and have plans for alternate water sources. As long as water levels in earthen impoundments remain low, water quality should be monitored regularly.