Water is the most essential nutrient for livestock production and is needed for numerous processes, such as the regulation of body temperature, growth, digestion, reproduction, metabolism, lubrication of joints, excretion, eyesight, etc. Water is also an excellent solvent for amino acids, minerals, glucose, vitamins, and metabolic waste.
Water requirements are influenced by a number of factors, including gestation, lactation, rate and composition of gain, type of diet, activity, environmental temperature, and feed intake. The intake of water from feeds plus the ad libitum consumption of free water is the equivalent of the water requirements in livestock. Ad libitum access to clean, fresh water is essential to maintaining feed intake in livestock. According to the NRC (1996), a wintering 1100 pound gestating cow needs to consume between 6 gallons at 40'F and 9 gallons at 70'F of water per day and the requirements double for a lactating cow. However, the requirements do not take in to account the distance cows must travel to the water source.
The water provided to livestock needs to be good quality to maintain production. Water quality may be altered by contaminants, such as mineral salts, toxins, heavy metals, microbial loads, debris, and agricultural practices. Most contaminants will reduce water intake, which results in a reduction in feed intake and a loss of production. However, if the water or feed contains increased salt, water intake will increase as the animal attempts to eliminate the excess sodium. Total dissolved solids (TDS) are measured to determine the saltiness of the water. Table 1 describes the recommendations and effects of increasing concentrations of TDS in the water.
Water with high concentrations of TDS, may have high concentrations of nitrates and/or sulfates. High sulfate concentrations in water can lead to polioencephalomalacia (polio). High sulfate water tastes bitter and water intake may be reduced. High concentrations of sulfate may also cause a reduction in copper availability in livestock, which can lead to copper deficiency. Producers should be aware of water sulfate concentrations when feeding high sulfur feedstuffs, such as distillers grains or corn gluten feed, and feeds containing high concentrations of molybdenum. If livestock are consuming high sulfate water, additional copper supplementation may need to be considered.
Similar to nitrates in forages, water with high nitrate concentrations can also be toxic. Nitrate from the water is converted to nitrite within the rumen, which can be toxic by decreasing the oxygen-carrying capacity of hemoglobin. Producers should especially be aware of water nitrate concentrations when feeding forages with high nitrate concentrations.
Other contaminants include bacteria, which can be toxic to livestock. High bacteria concentrations can cause infertility, foot rot, low milk production, and other reproductive problems. Stagnant water that is contaminated with manure and other contaminants can develop blue-green algae, which may be toxic to livestock. It is crucial to maintain a clean, fresh water supply to maintain health and performance of livestock.