Water; Vital to Beating Summer Heat

By : Aerica Bjurstrom, UW-Extension Kewaunee County

Water is the most important nutrient an animal requires and consumes daily. Depending on weight, production stage, and environmental temperature, cattle require varying amounts of water. A University of Georgia publication suggests for cattle in 90 °F temperatures, a growing animal or a lactating cow needs two gallons of water per 100 pounds of body weight. A nonlactating cow or bull needs one gallon of water per 100 pounds of body weight. Using these figures, a single cow/calf pair can require roughly 25 to 40 gallons of water daily. A nursing calf with have a portion of its daily water needs from its dam’s milk. Providing multiple water sources or tanks in the pasture will increase consumption and decrease competition and fighting at the water tank.

Water quality is just as important as water volume intake. Compromised quality can reduce water intake, which can lead to illness and metabolic issues. Testing water for salinity, nitrates, and sulfates is recommended. Cattle prefer water that contains small amounts of salt, however, water that contains high amounts of total dissolved salts (TDS) can result in reduced performance. Guidelines suggest that water containing 3,000 ppm TDS or less is usually acceptable for most livestock. In addition, water with salinity over 5,000 ppm TDS can act as a laxative and dehydrate cattle. Water more than 5,000 ppm TDS should not be fed to pregnant or lactating females.

Nitrates pose another issue for cattle. Nitrates are converted in the rumen into nitrites. While nitrates are not harmful to cattle, the conversion into nitrites can be toxic to cattle. Nitrites are absorbed into the bloodstream and convert hemoglobin to methemoglobin. Methemoglobin does not bind to oxygen, and the oxygen carrying capacity of the blood is reduced. A safe level of nitrate nitrogen (NO3N) in the water for cattle is less than 100 ppm.

Sulfates can be found in feed and water. Testing water for sulfates can help you manage health risks to cattle by understanding how much they consume daily. The safe upper limit of sulfate consumption is 500 mg/L (ppm) (167 ppm sulfur as sulfate). Unsafe levels of sulfates may lead to polioencephelomalacia (PEM), a brain disorder in cattle, and cause digestive absorption issues. Distillers grains are also high in sulfur, so intake should be monitored in both water and feed sources.

Additional substances in water can cause decreased intake and potential health issues. High or low pH and excessive iron are common issues in Wisconsin. While these issues are not typically lethal, they can result in an “off flavor” which can reduce intake.

Dehydration and heat stress can set in quickly on hot summer days. Monitor the herd for open mouth breathing, sunken eyes, “Skin tent” after pinching skin, yellow or dark urine, and/or fever. Fever is indicated by a rectal temperature of more than 102.5 F.

Forage can impact how an animal deals with heat stress. Low quality forage has been shown to increase rumen temperature, therefore increasing internal temperature. Quality forage not only helps your cows metabolize at a healthier rate, it also can reduce the likelihood of higher internal body temperature. Providing shade when possible and fly control (either chemically or naturally with good ventilation/air flow) will reduce stress on animals as they seek a cool place to rest.

Good management can help your herd beat the heat this summer.

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