Drought '02 Ohio State University Extension Drought Stressed Corn for Silage Bill Weiss - Animal Sciences Department, OARDC Much of Ohio is under drought conditions and producers are concerned about chopping corn for silage. Below are some answers to common questions. Q. When should I chop corn for silage? A. It depends! The most important factor affecting when to chop corn is its dry matter concentration. Corn chopped too wet ferments very poorly and feed intake is reduced greatly when it is fed. Corn chopped too dry ferments poorly, has low starch digestibility and spoils quickly during feed out. Corn should be chopped when its dry matter is between about 30 and 40% (equal to 60 to 70% moisture). Ideally the dry matter should be between 32% (for bunkers) and 38% (for upright silos). Do NOT chop corn for silage when its dry matter is less than 28%. Feed intake by cattle is usually much lower when fed very wet silage. Before a farmer starts to chop, he should go to the field and cut a few (3 or 4) stalks at the same height as he plans on setting the chopper. Cut the stalks into small pieces (about 1 inch) using a cleaver or heavy knife, mix the sample and then analyze the sample for dry matter using a Koster tester or microwave (see OSU Agronomy Fact Sheet AGF-004-90). If the corn has the correct dry matter, he can chop the field. If it is too wet, delay chopping. Q. What about nitrates? A. See Animal Science Fact Sheet AS-0003-90 for more details. Drought-stressed corn often accumulates nitrates. Nitrates are toxic to ruminants. This year all corn silage should be tested for nitrates before feeding. Nitrates are often not a problem during prolonged drought but can become very high when prolonged drought is followed by rain. After a rain, the soil nitrates move into the plant. Silage fermentation usually reduces the concentration of nitrates in silage. Fresh plants can have excessive nitrates but the resulting silage might be safe to feed. Therefore, knowing the concentration of the feed after fermentation is more important than knowing the concentration of nitrates in fresh corn plants. It nitrates are suspected, sampling fresh material can be useful however. Before chopping starts, sample a few plants from the field (cut at the same height as the chopper) and send in the sample. If values are low, you should have no problem. If values are high, chopping height should be increased because most of the nitrates are in the lower portion of the stalk. Guidelines for nitrate concentrations are below (make sure the lab values are in the same units) <0.1% Nitrate-N (dry matter basis): Feed is safe 0.1 to 0.2% Nitrate-N (dry matter basis): Feed is probably safe, limit to no more than 50% of the diet for pregnant animals 0.2 to 0.35% Nitrate-N (dry matter basis): Do not feed to pregnant animals, limit to less than 50% of diet for other animals >0.35% Nitrate-N (dry matter basis): High risk, should not be fed. Q. Are there any human health concerns? A. Yes. High nitrate corn when put into a silo produces large amounts of gases. These gases (mostly nitric oxides) can be lethal. If you see a yellow-orange gas cloud around a silo, keep humans and animals away from it. Q. Are silage additives useful with drought-stressed corn? To reduce nitrate concentrations, a rapid and active fermentation is needed during silage making. A good quality silage inoculant might help increase fermentation which could lower nitrate concentrations. On the other hand, acids and ammonia reduce fermentation and should probably not be used for drought-stressed corn. Q. What is the feeding value of drought-stress corn? A. Assuming it was chopped at the correct dry matter and is low in nitrates, drought-stressed corn silage is a reasonably good feed for cattle. It usually has more fiber and less grain than normal silage but the fiber is usually more digestible. The net result is that the energy value is usually slightly lower than normal silage and additional grain supplementation might be needed. Drought-stressed corn silage must be tested for nutritional value so that appropriate diet changes can be made.   All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status. Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension. TDD No. 800-589-8292 (Ohio only) or 614-292-1868   | C.O.R.N. | Newsletter | Ohioline | Publications |