Water requirements for pastured livestock
When raising livestock, ensuring access to a steady supply of fresh drinking water is a constant challenge.
According to the Prairie Farm Rehabilitation Administration, the total water needs of livestock are met through water contained in feed supplies, as well as additional water that must be supplied separately from feed. This so-called "voluntary consumption" depends on several physiological and environmental factors:
Size and type of animal
Physiological state (pregnant, lactating, growing) - lactating cows require about an extra 0.86 kg of water for every kg of milk produced, and water intake during the latter stages of pregnancy can be 30-50% higher than normal
Activity level - more active animals consume more water
Type and amount of diet - animals fed on dry feed will require more voluntary water than those fed on silage or lush grass
Weather conditions - water consumption increases as air temperature increases
Water quality - more palatable water or greater total salt intake will result in increased water consumption
Ease of access - animals will consume less water if they have to travel further to the source, or if access to the source is awkward and uncomfortable.
All other factors being equal, the primary variable affecting water consumption is temperature, so the following table is divided into winter and summer.
Source: The Stockman's Guide to Range Livestock Watering from Surface Water Sources
Water quality is important
Water quality can affect both total water consumption and the general health of the livestock. Elevated water temperatures and objectionable taste and odor will discourage consumption, and reduced water consumption will, in turn, result in a reduction of feed intake, with the net result being decreased weight gain.
The most common water quality considerations that make water unsuitable for livestock consumption are salinity (the concentration of various kinds of dissolved salts), nitrates, algae, and on rare occasions, other factors such as alkalinity or pesticides.
Dissolved salts can consist of any combination of calcium, magnesium, and sodium chlorides, sulfates and bicarbonates. While all have slightly different effects on animal metabolism, none are particularly worse than any other. Also, the effects of various salts seem to be additive, meaning that a mixture seems to cause the same degree of harm as an equivalent concentration of a single salt. Animals seem to have an ability to adapt to saline water to some extent, but abrupt changes may cause harm. Animals may avoid drinking highly saline water for a number of days, followed by a period of high consumption which causes illness or even death.
Water analyses generally report nitrates and nitrites together. Nitrate toxicity resulting exclusively from water is rare, but is primarily of concern when combined with forages having high nitrate levels. Nitrates themselves are not very toxic, but bacteria in ruminant animals (dairy and beef cattle) will convert the nitrates to nitrite which reduces the blood's ability to metabolize oxygen and effectively causes shortness of breath and eventual suffocation.
Although sulfates can have a laxative effect, there is limited data available regarding their overall effect on livestock health and productivity. It is generally felt that the presence of sulfates should seldom be a problem in livestock water. However, in some rare cases involving very saline water, producers have lost cattle due to a sulfate-related problem.
Excessive alkalinity can cause physiological and digestive upset in livestock, but the level at which it becomes troublesome and its precise effects have not been thoroughly studied. Most waters are alkaline in nature, but fortunately, in only a few instances has it been found that a water source has been too alkaline for livestock. Alkalinity is usually expressed as a concentration of Calcium Carbonate (CaCo3), in parts per million (ppm) or milligrams per litre (mg/L).
Most water has varying levels of bacterial contamination, but such contamination does not generally cause problems for livestock. Calves can sometimes suffer from Coccidiosis, which can lead to bloody diarrhea, dehydration, weight loss, depression, and sometimes death. Elevated water sources and a reasonable effort at maintaining cleanliness of watering facilities can reduce the potential for problem-causing bacterial contamination.
Certain species of algae (blue-green algae) can, under some circumstances, be toxic. At present, there is no test available for these toxins. Other than possible toxicity, the presence of algae in livestock water supplies will affect livestock indirectly by discouraging consumption due to reduced palatability (taste and odor). Algae blooms can be prevented from occurring in a water supply by aerating the water and by preventing excess nutrients (phosphorus, nitrogen) from entering the water. The primary source of nutrients that contribute to aquatic plant growth are animal excrement, fertilizers and organic matter like grass, hay, leaves and topsoil.
Generally speaking, any surface water that can support a population of fish should not have dangerous levels of pesticides or naturally-occurring toxic elements like heavy metals. However, there is growing evidence that toxic compounds are present in many surface waters across the prairies. If there is any reason to believe that a water source may have elevated levels of toxic compounds, they can be tested for.
It is recommended that water samples from the intended source be analyzed to ensure that any problems relating to water quality can be avoided.
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