Water: The Forgotten Nutrient
As summer heats up, water becomes more important for cattle. An animal’s body is comprised of 70% water and adequate water consumption is required to maximize performance. It’s no secret that withholding or restricting water can decrease feed intake and reduce gains. Yet many producers often forget to assess whether or not their animals have optimal access to high quality water. An animal’s water requirement is met through consumption of feed and drinking. Many feeds, such as silage and grasses, contain a large proportions of water that help cattle meet their water requirement. Additional requirements are met through drinking.
Water Requirements and Intake
Water requirements vary depending on the physiological state of the cattle. Reproductive status, lactation status, rate and composition of gain, and amount of physical activity will affect how much water cattle need to consume. Lactating cows will consume more water, on average, than growing, finishing, or pregnant cattle (Figure 1).
Temperature will also affect water requirements, with higher temperatures increasing voluntary water intake for all cattle regardless of physiological state (Figure 1). For lactating cows, water intake will increase by over 23% when the ambient temperature rises from 60 to 80°F. Across a similar temperature shift, growing cattle will increase their water intake by 35%.
Management factors, such as diet composition and physical access and palatability of drinking water, also affect how much water cattle drink. Because of their higher moisture content, diets that contain a high proportion of silage or pasture can reduce the amount of water consumed through drinking. Diets that contain high levels of protein, salts, or other diuretics will increase water intake through drinking.
Not only is it important for cattle to have access to sufficient quantities of water, the quality of that water is also important. Water quality is assessed by examining factors such as palatability, chemical properties (e.g., pH, dissolved solids, hardness, soluble salts, etc.), presence of toxic compounds, mineral content, and presence of harmful bacteria (e.g., coliforms).
The level of total soluble salts can provide some indication of water quality. Of the soluble salts, sodium chloride (NaCl) is often a major driver of the total soluble salts content in water. Other major contributors to the total soluble salts content include: bicarbonate, sulfate, calcium, magnesium, and silica. High concentrations of soluble salts can decrease water intake and ultimately reduce production. Total soluble salt concentrations less than 1,000 mg/L are ideal. Levels above 3,000 mg/L may start to impact production and water with total soluble salt concentrations over 5,000 mg/L should not be used as a primary drinking source for pregnant or lactating cows.
The concentration of certain minerals can also be used to assess water quality, with nitrate and sulfate concentrations being of most interest. Nitrate concentrations below 44 mg/L are considered safe for all types of cattle to consume. Over short periods of time, cattle can tolerate nitrate levels up to 221 mg/L with modest effects on production and health; however, concentrations above 221 mg/L can result in significantly reduced production and serious health problems. Cattle can generally tolerate sulfate concentrations up to 2,500 mg/L for a short duration (up to 90 days), although concentrations less 500 mg/L and 1,000 mg/L are considered ideal for calves and adult cattle, respectively.
Other compounds are also used to assess water quality. The table below shows the recommended upper limits of several compounds.
|Upper Limit (mg/L)
National Academies of Science, Engineering, and Medicine. 2016. Nutrient Requirements of Beef Cattle, Eight Revised Edition. Washington, DC: The National Academies Press. doi: 10.17226/19014