Considerations for harvesting drought-stressed corn to feed to cattle

Image Credit : University of Kentucky

Donna Amaral-Phillips, Jeff Lehmkuhler, and Chad Lee

Extension Dairy Specialist, Extension Beef Specialist and Extension Agronomist, University of Kentucky

Even with recent rains, some corn was too damaged by droughts to produce adequate yields. Some drought-stressed corn can be salvaged as cattle feed. Here are some things to consider if harvesting drought-stressed corn.

When Considering Your Harvest Options:
1. If corn is going to be fed as green chop, grazed, or as hay, test for nitrates before harvest to be sure the crop will be safe to feed. For corn harvested properly as silage or baleage and which goes through a good fermentation, nitrate levels could decrease 30 to 50% and can be tested after fermentation and before being fed. If you need to decide which corn fields to harvest as silage or hay, testing before harvesting will allow one to determine which fields need to be harvested as silage (those higher in nitrates) and those with safe levels of nitrates which can be harvested as corn hay. For sorghums and sorghum-sudangrasses, nitrates should be tested before harvest to be safe for your harvest method.

2. Check herbicide withdrawals to make sure the crop can be fed to livestock. Read the herbicide labels to identify if feeding restrictions are in place. 
3. Raise the cut height—nitrates are highest in the plant stem closer to the ground. This may be more difficult if using a disc mower or other hay equipment for the purpose of making hay or baleage.
4. If at all possible, harvest as silage and let ferment for 4 to 6 weeks before feeding. You may want to consider using a silage inoculant. Again, test for nitrates before feeding.
5. Immature corn will be more variable in nutrient content than “normal corn silage”. After harvest, test the forage for its nutrient content and develop and feed a balanced ration to your cattle. Making a yield estimate prior to cutting corn will be a challenge if corn is harvested before the dent stage.
6. Watch the moisture content of the crop closely. Corn silage should be harvested between 62-65% moisture (35-38% dry matter).  A small amount can be chopped to determine the current moisture content. Corn is drying down quickly in parts of Kentucky. Use a Koster tester (preferred) or microwave (acceptable, but be prepared to buy a new one for the house) to determine the actual moisture content. Silage and baleage need to be correct moisture to ferment properly and make good feed.  Corn silage harvested at or less than 60% moisture (at or greater than 40% dry matter) results in a lower animal performance and should be avoided.

7. Tonnage may be low. Most corn is harvested for silage when the kernel is between ½ to ¾ milkline . In a healthy cornfield, the ear will make up half the total silage weight. Corn harvested before seed development will be much lighter.

8. Corn harvested early for silage will not have as much grain and the energy value of the subsequent silage will be less than normal. If the corn is severely drought-stressed, it will not make full kernels anyhow, and silage is an excellent option, but it will have a different feed value than “normal” corn silage. The corn silage should be sampled for nutrient analysis after fermentation and cattle rations should be adjusted accordingly.
9. Can you add enough water at the bagger or silo blower to increase the moisture content of the silage? For each 1% increase in moisture content, approximately 7 gallons of water is needed per ton. A typical garden hose delivers approximately 8-10 gallons per minute. Thus, it is nearly impossible to deliver enough water to make a difference. For example, to increase the moisture content from 45% moisture (55% dry matter) to 60% moisture (40% dry matter) for a wagon load of silage (4 ton capacity), you need to add 420 gallons of water. That is not feasible!!

Can you make baleage out of corn? Yes- but moisture and other harvesting techniques are important.
1. Moisture content needs to be between 30 to 50% for baleage. Getting the crop at the moisture content can be very challenging.
2. Plant material needs to be crimped and/or conditioned before baling. Conditioning is a must to get the crop to ferment. Using a rotary mower (i.e. bushhog) may also work but make sure the blades are sharp to reduce shredding of the corn plant. If your baler has knives, they can be used to chop the corn plant.
3. Newer balers work the best. This is a very coarse crop that is tough on hay equipment and some older style balers may have difficulty handling the crop.
4. Inoculant can be added at the baler, if you are equipped to handle this.
5. Wrap with at least 2 extra layers of plastic for a total of 7 layers of plastic due to corn stalks puncturing the plastic.
6. Net wrap may work better than string tie balers. If you use a string tie baler, additional wraps of string should be used.

Can you make hay out of the crop? YES--- BUT
1. Nitrates will not decrease from the standing crop. The crop needs to undergo normal fermentation to decrease the level of nitrates. Hay does not ferment!!! If nitrates are high in the standing crop, they will not decrease with harvest and hay storage.
2. Whole plant moisture needs to be about 15% for hay. If the crop is harvested with over 18% moisture, it will heat and make a very poor feed. It can spontaneously combust if too wet and goes through a heat.
3. Corn stalks protein and energy content will vary.  Bales should be sampled for nutrient analysis and  the hay may require supplementation depending on the cattle being fed.

Can you graze the corn left standing in the field?  YES-BUT

1.     Fencing and watering is a necessity for the livestock.

2.     Strip-grazing is needed to reduce the risk of foundering/acidosis.  Cattle will quickly learn to consume the ears first increasing starch intake.  Using strip-grazing will increase intakes of leaves and upper portion of the stalk to reduce grain intake.

3.     Consider a grass area for cattle to loaf/lay.

4.     Provide free-choice access to hay.  This will increase fiber intake and lower the risk of rumen digestive disorders.  Hay intake can also be used as a gauge of corn allocation.  As cattle consume more hay, this could mean they have consumed as much of the leaves, stalks, and ears from the area provided and a new section of standing corn should be provided.

5.     Nitrate toxicity is a risk.  However, most of the nitrates are in the lower portion of the stalk that cattle tend to avoid consuming.

6.     Have a pasture area to move cattle to during periods of high precipitation to limit compaction.