Water Quality for Livestock
Water is the nutrient required in the largest quantity for beef and dairy cattle. A beef cow can drink up to five percent of its body weight in water per day; a high-producing dairy cow, up to 20 percent. A lack of water will have a rapid and dramatic effect on animal health and productivity.
A safe water supply is essential for healthy livestock and poultry. Contaminated water can affect growth, reproduction, and productivity of animals as well as safety of animal products for human consumption. Contaminated water supplies for livestock can also contaminate human drinking water. For these reasons, farm water supplies should be protected against contamination from bacteria, nitrates, sulfates and pesticides.
Water quality recommendations in this article pertain only to livestock and poultry, not to human drinking water. The Environmental Protection Agency has set drinking water standards for human consumption, but no set of standards exists for drinking water for livestock. The National Academy of Science, however, has recommended maximum levels for some contaminants.
Sources of Contamination
Coliform- These are organisms found in the gastrointestinal tract of livestock, humans and birds. While these bacteria may not be harmful, their presence often indicates that other disease-causing bacteria may also be present. The main source of coliform bacteria is animal waste. Where large numbers of animals are concentrated near shallow or poorly protected wells or ponds, bacterial contamination can occur during heavy rainfall.
Blue-Green Algae- Toxic blue-green algae can contaminate surface drinking water supplies. In livestock, blue-green algae poisoning causes muscle tremors, diarrhea, lack of coordination, collapse, labored breathing, liver damage, and death. Algae grow and multiply because of favorable nutrient and temperature conditions.
Nitrates- Nitrates by themselves are not very toxic. However, in the rumen of cows or sheep, microorganisms change nitrates to nitrites, which are quite toxic. Nitrites are further acted upon by microorganisms and converted into protein. In cows or sheep that consume large amounts of nitrates in short periods of time, however, nitrites accumulate faster than they can be built into protein. These excess nitrites are absorbed into the bloodstream. There the nitrites react with the hemoglobin (the red oxygen-carrying pigment of the blood) to form methemoglobin, which prevents the blood from carrying oxygen. If a large portion of the hemoglobin has been converted to methemoglobin, the animal shows symptoms of asphyxiation including labored breathing, a blue muzzle, a bluish tint to the whites of the eyes, trembling, a lack of coordination, inability to stand, and often death.
Sources. Some sources of nitrates in groundwaters include nitrogen fertilizers, animal manure or wastes, crop residues, human wastes, and industrial wastes. Since nitrates are soluble and move with percolating water, groundwater pumped from a well may contain nitrates even if their source is a considerable distance from the well.
Sulfates- Excessive concentrations of sulfates cause a laxative effect in animals, which is more pronounced in young than in mature animals. In young animals, sulfate concentrations in excess of 350 to 600 ppm may be associated with severe chronic diarrhea and electrolyte imbalance.
Sources. Sulfates appear in water when they are dissolved as water moves down through soil and rock formations. Human activities have little effect on the concentration of sulfates or other dissolved minerals in groundwater supplies.
Pesticides- Many pesticides are readily broken down and eliminated by livestock with no obvious ill effects, but there is a possibility that some could be excreted in milk or accumulate in meat. Fish are more sensitive to pesticides than are livestock or poultry.
Sources. Pesticides can enter a surface water or groundwater supply from runoff, drift, rainfall, direct application, accidental spills, faulty storage facilities, and faulty waste disposal techniques. Of the pesticides currently in use, the organophosphates are the most dangerous for livestock.
Salinity- The damage of high saline water depends more on the total amount of minerals present rather than on any specific one. The ions most commonly involved in high saline waters are calcium, magnesium, sodium, bicarbonate, chloride, and sulfate. Usually chlorides are less harmful than sulfates. Magnesium chloride appears to be more injurious than calcium or sodium salts.
Sources. High saline waters can be located where there is saline intrusion in the water. Limits. The table at the right gives the National Resources Council recommendations on saline waters for horses and other animals.
Iron- There is no evidence to show that iron will cause any problems with livestock or poultry. According to Report Number 26 of the Council for Agricultural Science and Technology, "Under usual conditions, water supplies only a small percentage of the iron available to animals. Because iron from natural sources is absorbed with efficiency less that 10 percent, the iron in water should not pose a hazard to animals. Under these circumstances, a 'no limit' recommendation is reasonable. High doses of the more available forms of iron, however, are toxic."
When water is suspected of causing health problems in livestock, an accurate diagnosis is crucial. A laboratory exam of both the animals and the water supply may be necessary to adequately diagnose the problem. A veterinarian may need to determine the actual disease. Since water is often blamed for problems caused by production or disease, temporarily changing to a known safe water supply is a useful test to determine if the water supply is causing the health problems.
The majority of this article consists of excerpts taken from extension publication wq-26.al of Auburn University (http://hermes.ecn.purdue.edu:8001/cgi/convertwq?7745).