UNIVERSITY PARK, Pa. -- Drought conditions across Pennsylvania increase the risk of nitrate accumulation in harvested corn and sorghum used as cattle feed, warns an animal health specialist in Penn State's College of Agricultural Sciences.

Extension veterinarian Robert Van Saun says dairy producers especially need to be aware of the danger to their animals posed by concentrations of the substance, which is a compound used by plants to synthesize proteins.

When plant nitrate is consumed by cows, Van Saun explains, rumen microbes convert it to nitrite and ultimately ammonia. "If excessive nitrite is accumulated in the rumen, it will cross into the blood and react with hemoglobin in the cow's red blood cells, preventing oxygen transfer," he says.

Affected cows will suffer of respiratory distress, weakness and ultimately death within one to four hours of consuming forage with excess nitrate, Van Saun points out. "If the consumed dosage is not enough to cause death, abortions may occur within two or three days," he says. "But animals can be treated if found early in the disease process."

According to Van Saun, diagnosis of nitrate toxicosis can be made on dead animals by the dark, "chocolate-colored" blood and measured nitrite concentrations in eye fluids. He offers some recommendations to minimize the risk of nitrate intoxication:

--Prior to feeding, analyze high-risk forages such as corn, sorghum, oats and other cereal grains grown under drought, low light levels, high nutrient loading or premature frost conditions for nitrate. "Do not feed green, chopped corn that has been stored overnight as it will have the highest potential for nitrate toxicity," warns Van Saun.

--Preserve high-risk forages as silage, not as hay. The ensiling process reduces nitrate levels by 30 to 50 percent, Van Saun notes.

--Minimize nitrogen addition to corn silage as fertilizer prior to harvest and don't add urea or anhydrous ammonia to increase protein content. "Forages high in nitrate will already have very high soluble protein levels," Van Saun says.

--Change feeds gradually, especially when the new feed is suspected of containing nitrates. Mix (dilute) high-nitrate forages with low-nitrate forages. Provide a well-balanced feed program. "Healthy animals on balanced rations are better able to tolerate nitrates than underfed animals," Van Saun says.

--If feasible, cut drought-stunted silage corn high 10 to 12 inches above the ground. "The highest level of nitrate in the plant is in the base of the stem or stalk," according to Van Saun.

--Test water supplies for nitrates. For more information about testing for nitrate, call your county's Penn State Cooperative Extension office.

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EDITORS: Contact Robert Van Saun at 814-865-6995 or e-mail rjv10@psu.edu.

Contact: Jeff Mulhollem jjm29@psu.edu 814-863-2719 814-863-9877 fax #260