Ohio State University (OSU) experts say producers should be paying close attention while testing drought-stressed corn for nitrate levels. Nitrate poisoning is a real concern for livestock production. Under normal growing conditions, nitrate is quickly converted to nitrite, then to ammonia, and finally into plant proteins and other compounds. When plant growth is slowed or stopped, nitrates can accumulate in the plant. Drought conditions, frost, or cool and cloudy weather can cause nitrates to accumulate. Extremely dry conditions can cause nitrates to accumulate in the lower portion of the stalk. When fed, the high nitrate levels can lead to calf abortions or toxic levels for adult cattle in some cases. Rainfall following an extended dry period may cause an immediate increase in nitrates for two to five days until the plant can convert the nitrates to protein.
OSU Extension in Defiance County, OH, coordinated the collection and testing of 64 corn plant samples from various farms in Defiance and Paulding Counties. The plants were collected on July 31 and Aug. 1 from fields with moderate to severe drought stress, normal to reduced nitrogen applications and low and high harvest height. Samples were delivered to the lab on each day of sampling. The range of percent nitrate on a dry basis was less than 0.01 to 0.27%. Samples less than 0.44% nitrate on a dry basis are considered safe to feed under all conditions. Percent moisture ranged from 63% to 76%. OSU is telling producers to keep in mind, rainfall received in some parts of Ohio on Aug. 4-7 will potentially affect the nitrate levels in field corn. A & L Great Lakes Laboratory in Ft. Wayne, IN, provides a chart outlining risk levels:
· Nitrate levels of 0.0 to 0.44% are considered safe to feed under all conditions.
· Nitrate levels of 0.45 -0.66% should be safe to feed to non-pregnant animals under all conditions. It may be best to limit its use for pregnant animals to 50% of the total ration on a dry basis.
· Nitrate levels of 0.67 to 0.88% can be fed safely if limited to 50% of the total dry matter in the ration.
· Nitrate levels of 0.89 to 1.54% mean feeds should be limited to about 35 -40% of the total dry matter in the ration. Feeds containing over 0.88% nitrate ion should not be used for pregnant animals.
· Nitrate levels of 1.54 to 1.76% mean feeds should be limited to 25% of total dry matter in rations. Do not use for pregnant animals.
· Nitrate levels over 1.76% are potentially toxic. Do not feed.
A & L Great Lakes Laboratory summarizes nitrate samples received into the lab in a report dated Aug 6th, available at http://www.algreatlakes.com/PDF/Corn_Forage_Nitrate_Summary_8_06_2012.pdf