Water, an Important Nutrient
A number of factors interplay and make water requirement and needs difficult to assess. Because feeds themselves contain some water and the oxidation of certain nutrients in feeds produces water, not all must be provided as drinking water. Feeds such as silages, green chop or pasture are usually high in moisture, while grains and hays are low. Feeds high in water content reduce water intake when cattle consume them. High energy feeds produce more metabolic water compared to low energy feeds.
As you think about water intake, it is mainly influenced by environmental temperature, class of livestock, and weight. This just makes sense. Water needs increase as temperature increases. Lactating cows have a greater need for water as compared to non-lactating cows. Data suggests that bulls have a greater daily water requirement than non-lactating cows and is likely a function of weight. As feeder cattle get heavier, daily water intake increases.
A University of Georgia publication lists the estimated water requirements for cattle in different production stages if the daily high temperature is 90 degrees F. Their data suggest for cattle in this environmental condition, growing animal or a lactating cow needs 2 gallons of water per 100 pounds of body weight. A non-lactating cow or bull needs 1 gallon of water per 100 pounds of body weight. As an example, spring calving cows will need close to 24 gallons per day for themselves and another 5 to 10 gallons of water for their calf in these high temperature environmental conditions. On days with extreme heat, expect the water usage to go up even further. Remember, some of that water will come from feed they eat and vegetative grass is high in water content. Also, for the nursing calf, a portion of the daily water needs will come from the dam’s milk.
Providing clean, fresh water is always a goal for the livestock producer. There are a number of items that affect water quality. Producer need to adapt management practices that do not negatively impact water quality.
Water that contains high amounts of total dissolved salts (TDS) can result in reduced performance. Cows will adapt to some salt in their water. Care must be taken if salt is used to limit intake of a feed in a free-choice supplementation management strategy. Cattle actually prefer water that contains very small amounts of salt. Research would suggest that water that contains a TDS of 5,000 ppm results in about a 10 percent reduction in performance. Guidelines suggest that water that contains 3,000 ppm TDS or less is usually satisfactory for most livestock. Water that contains 5,000 to7,000 ppm TDS should not be used for pregnant or lactating females.
Nitrates themselves are not poisonous to cattle; however, in the rumen, nitrates are converted to nitrites and nitrites and absorbed into the bloodstream and converts hemoglobin to methemoglobin. Methemoglobin does not bind to oxygen and the oxygen carrying capacity of the blood is reduced. Cattle can be adapted to nitrates, but it must be done slowly. However, it is stilled advised to avoid high nitrate water as a source for livestock. A safe level of Nitrate Nitrogen in the water for cattle is less than 100 ppm. Water over 100 ppm NO3N needs to be managed when used as a part of cattle’s diet. Remember, total nitrate intake would be the sum of the nitrates contained in both the feed and water consumed.
Animals can become acclimated to the sulfates in water. Consider diluting high sulfate water with low sulfate water for newly arrived animals. The sulfate recommendation for calves is less than 500 ppm (167 ppm sulfur as sulfate). For adult cattle the recommendation is less than 1,000 ppm (333 ppm sulfur as sulfate). Caution is required in evaluating sulfate levels in water because of interactions with copper and molybdenum and the inhibiting effect compounds such as sodium fluoride have on sulfate absorption for the digestive tract. In addition, high levels of sulfates may also contribute to an increased incidence of polioencephelomalacia (PEM), a brain disorder found in cattle. If copper deficiency problems are suspected, water sources should be analyzed for sulfates to determine if high sulfate levels are contributing to the problem. Remember, distillers grains can be high in sulfur and sulfur intake is the amount from the feeds and water consumed.
Stagnant water is an excellent environment to develop blue-green algae that can be toxic to cattle. The scum that you see on the inside of stock tanks is algae. Ponds seem to be the most common reservoir for blue-green algae. Toxicity is most common after rapid bloom normally occurring in late summer when cattle have their greatest water consumption. Toxicity as a result of blue-green algae is difficult to predict. Algae blooms can be controlled in a pond by using copper sulfate (blue stone). Be aware that a rapid die-off of algae may result in killing fish. Contact your extension person for guideline for the amount of copper sulfate to use. The best way to control blue-green algae is to eliminate the source of nutrients entering the pond.
Water is the most important nutrient for cattle. Daily provide a clean supply of water for your cattle. As you think about developing grazing systems, the water system will impact grazing distribution.
[June 21st, 2011]
Dr. Rick Rasby, Professor of Animal Science
Animal Science, University of Nebraska - Lincoln, Lincoln, NE