Dairy Channel: Even rain won’t dispel worries over quality of this year’s dairy feed

Hot and dry. These conditions are troubling farms not only in Ohio, but also in Kentucky, Illinois and other states, according to just a few of the 1,000-plus agriculture extension agents gathered in Savannah, Ga., this week for the 87th annual meeting of the National Association of County Agricultural Agents.

Because of that heat and lack of moisture, crop conditions and the coming year’s forage supplies are on your mind. By noon, cornfields look like Dole should be scouting for a pineapple crop. Fields trying to tassel now look sad. Thoughts are turning to early harvest and minimizing losses.

Lessons learned. Two previous experiences with drought, in 1988 and 1999 taught us some lessons that we need to remember. Today’s hybrids showed us an unexpected ability to withstand periods of drought. When rain finally came, many fields came back and produced more forage than we thought possible.

Even though this year’s feed nutrient values may be unique and yields will be down, corn silage is still likely to be the best forage value for the dollar.

To help answer increasingly-asked questions about chopping corn for silage, Bill Weiss, OSU Extension Dairy Specialist addresses these 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 percent (equal to 60 to 70 percent moisture). Ideally the dry matter should be between 32 percent (for bunkers) and 38 percent (for upright silos). Do NOT chop corn for silage when its dry matter is less than 28 percent.

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 (three or four) 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. Drought-stressed corn often accumulates nitrates. (See Animal Science Fact Sheet AS-0003-90 for more details.) 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 in the feed after fermentation is more important than knowing the concentration of nitrates in fresh corn plants.

Testing for nitrates. If nitrates are suspected, sampling fresh material can be useful.

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.


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?

A. 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-stressed 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.

Check with your county agriculture extension agent for copies of the drought fact sheets mentioned by Weiss, or the Ohioline Web site at http://ohioline.osu.edu/.

Meanwhile, I’m going to grab a peach and check out a few of Georgia’s poultry, peanut and Vidalia onion farms. I’ll be hoping for rain at home.      

(The author is the northeast Ohio district dairy specialist with OSU Extension. Send comments or questions in care of Farm and Dairy, P.O. Box 38, Salem, OH 44460.)

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