Green grass is a welcome sight, especially for everyone coming out of “the winter that wouldn’t end.” And as cattle head to summer pasture, focus is on the high-quality nutrition available in that new growth. But there is one essential nutrient – actually, the most essential nutrient – that still merits our attention. Water must be available in adequate quantity and quality to support functions ranging from digestion and milk production to blood volume, joint lubrication and waste transport.

Despite the importance of water intake, there is limited research available on measureable impacts of restricted intake or poor water quality. The NRC “Nutrient Requirements of Beef Cattle,” in fact, only devotes 1 ½ pages to water as a nutrient, and a large portion of that is a table that dates back to 1956! We do know an animals’ requirement for water is driven by a combination of factors: size, feed intake, rate and composition of gain, milk production, activity, ration composition, and of course climate. As the temperature rises from 40 to 90 degrees F, cattle will double the amount of water they drink.

Diet impacts water needs several ways. First, as animals eat more, water consumption must increase as well. Because feedstuffs vary greatly in moisture content, cattle will meet varying portions of their water requirement through different diets; this naturally affects the volume that needs to be consumed in liquid form. And salt intake is directly linked to water requirements; for every pound of salt consumed, cattle must drink an additional 5 gallons of water. This can come into play when salt is being used as a limiter in free-choice supplements.

Animal Drinking Behavior
Knowing how and when animals drink can have management implications. With adequate access to water, cattle will drink 2 to 5 times per day. However, in extensive grazing situations, less frequent drinks will lead to less total intake – and presumably, less feed intake as well. If cows have to travel ¼ mile or more to their water source, they will tend to make those trips as a group. If that trip is less than 900 feet, they are much more likely to come individually or in pairs. In situations where the whole herd will typically come together, there needs to be enough tank capacity to handle 25% of the groups’ daily needs at once. It is also important to have enough access for 10% of the animals to drink at once.

For example: in a herd of 100 cows, there needs to be room for 10 head to drink at once, or about 20 linear feet. Since circumference = diameter multiplied by p, we can see this could be accomplished with a 6-foot diameter tank (6 X 3.14=18.8). However, this may not be large enough to hold 25% of their daily need. If we use the figure of 20 gallons/head/day, this same herd would drink 2000 gallons a day, and 25% of that is 500 gallons. In this case, they may need a larger tank, or two tanks placed so that distance to water is reduced throughout the pasture (causing fewer animals to come drink at once). Producers need to balance between size, number, and location of water sources to best fit the needs of their operation.

Quantity Issues
When water availability is restricted, cattle will immediately respond by decreasing feed intake. This has an obvious impact on growth and reproductive performance. Conversely, if animals have access to relatively high-moisture feeds (such as liquid supplements or some byproducts), they may try and consume excessive amounts of these to make up for the shortage. Metabolically, cattle have a very low tolerance for dehydration, and a 10% loss in body water is severe. And because one of the roles of water is toxin removal, limited water intake can lead to a dangerous build-up of these compounds in the animal.

Quality Issues
Water may contain several types of contaminants that can potentially have a negative impact on animal nutrition, performance and health. These

 Level Assumed Safe for Most Classes of Livestock (NRC)
 Nitrate-N, ppm
 Nitrite-N, ppm
 Sulfate, ppm
 Total Dissolved Solids (TDS) ppm

may be naturally occurring (i.e., high mineral levels due to local soil content), due to run-off of chemicals or excess nutrients, or involve dangerous levels of microorganisms. The upper “safe” limit for compounds that are of frequent concern are shown in the table to the right.

Several published research trials have found that if there are no particular quality concerns, animals receiving water from a pond or dugout performed as well as those with access to fresh water. However, when contaminant concentrations exceeded recommended levels, significant effects have been observed. Several studies have been done at South Dakota State University with high-sulfate water. When rural/tap water was substituted for well or dam water, intake of both feed and water were increased, along with gains, feed efficiency and health status in steers, and body condition in cows. Colorado feedlot research demonstrated a reduction in ADG, conversion and carcass characteristics with water sulfate levels of 583 ppm. In studies where sulfates were in the 3500-4000 ppm range, water intake was observed to drop 35 to 57%.

High levels of some minerals, such as iron, have been shown to interfere with absorption of other essential TM such as copper. Some of these compounds, while necessary at a certain level, are directly toxic in excess. Concentrations in water can vary greatly, even within a fairly narrow geography, so testing is important if concerns exist.

One unique problem that can occur periodically involves the rapid growth of what has been inaccurately named blue-green algae. This is in fact a cyanobacteria, and the combination of warm temperatures and high nutrient concentrations(nitrogen and phosphorus in particular) can lead to a population explosion, and “blooms” in ponds. Two different toxins are formed: a neuro-agent that causes rapid death, and one that causes liver damage and leads to a slow death. Neither are treatable. If conditions are right (warm weather and drying out ponds or flood overflows), color is apparent in the water, and especially if dead rodents or snakes are found near the pond, remove all livestock and have a water sample tested.

Management Principles
- Consciously evaluate water access (volume and drinking space) relative to herd size;
- Consider using fencing, and possibly pipe, to limit or exclude animal access to ponds. This can significantly reduce nutrient and bacterial contamination and build-up;
- Manage fertilization and manure handling programs to minimize nutrient run-off;
- If water of marginal quality must be used, consider the following:
o Use for animals with lowest needs (low-production, cool weather).
o Adjust the mineral program to compensate for reduced absorption.
o Wean early, to reduce maternal water requirements.
o Limit use of sulfur-containing feeds and supplements.
o Pipe water from a creek or stream to tanks (running water usually has lower sulfate levels than ponds).
Water is a critical and limited natural resource, and going into the future, management of this most important nutrient will undoubtedly gain in importance.

Source: Dr. Cathy Bandyk, Quality Liquid Feeds, Dodgeville, WI