What About Nitrate Content? Stressed corn can have elevated nitrate levels. However, samples collected from previous drought years indicated nitrates were not a problem in most cases. For example in 1988, based on 70 fresh corn samples, only 18% contained toxic levels of nitrate. In contrast, 71% of the sorghum-sudan grass samples contained toxic levels of nitrate.
Quantitative laboratory analyses for nitrate can be performed at the Purdue University Animal Disease Diagnostic Laboratory (ADDL). Cost is $15.00 per sample plus $7.00 accession fee per individual each time samples are submitted. A one-quart size sample of chopped forage is adequate. Samples should be submitted in paper bags or cardboard boxes, not in sealed glass or plastic containers. Names and addresses of other laboratories to obtain nitrate tests can be found at
http://www.ansc.purdue.edu/beef/Hendrix ... trate.html.
Also, during the fermentation process, 40 to 60 percent of nitrates will be eliminated. Keep in mind, however, that various nitrogen oxide gases produced during the fermentation process are highly toxic to humans and livestock. For the first three to four weeks after ensiling, do not enter a silo without first running the blower for 15 to 30 minutes.
Harvesting for Green Chop. In cases where pasture and stored feed supplies are getting short, producers may wish to consider green-chopping corn for feed. There are two major concerns with this practice. One is the potential for nitrate toxicity and second is the potential to founder animals. To avoid these problems: (1) raise the cutter bar to 12 inches or so the first few days of chopping, (2) gradually introduce animals to green chop, (3) use other feeds that are low in nitrate as part of the ration, (4) feed green chop in small quantities throughout the day rather than large quantities once per day, (5) don't allow green-chop forage to set on a wagon overnight, (6) feed two to three pounds of grain with high nitrate feeds, (7) nitrate levels tend to increase for two to three days following rain, thus take extra precautions during this time period, (8) as plants mature, nitrate levels decline, also animals become acclimated, thus chances for toxicity decrease with time.