Stressed corn crop can kill livestock

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SALEM, Ohio – Although many corn fields in Ohio and Pennsylvania have benefited from scattered showers in the past weeks, other areas haven’t been as fortunate.
The corn crop is showing the stresses of hot, dry weather, and many farmers wonder what yields will look this fall.
Feeding drought-stressed corn can kill, so experts are warning farmers to take precautions before feeding new crop corn or corn silage to their livestock.
Silk. Reports of short, waist-high corn tasseling and uneven flowering in fields are coming in from parts of the state, according to Ohio State crop specialist Peter Thomison.
Many corn growers are concerned about the impact drought stress has had on corn pollination, the most sensitive stage in corn development.
When severe drought stress occurs before and during pollination, a delay in silk emergence can occur.
Depending on your area, it’s possible little or no pollen was available for fertilization when the silks appeared. That means there’s a chance the ears of corn in your fields may not have any kernels on them.
“This year it’s very likely that silk emergence will be delayed in many drought-stressed corn fields unless we get some significant rain very soon,” Thomison said.
Livestock. Livestock producers should consider several guidelines when making decisions in the next few weeks when and if to harvest their drought-stressed corn silage.
Dick Wallace, a University of Illinois veterinarian, is recommending producers locate alternate forages or consider chopping drought-stressed corn.
There’s a degree of risk in feeding 2005 crop corn: Several crop species can accumulate nitrates, especially grasses such as corn, oats, wheat, barley, and sorghum.
A buildup of nitrates can kill even the healthiest cow.
Safe levels. Setting the cutter bar higher on the corn chopper will leave more stalk residue in the field, leaving more nitrates behind, Wallace said.
The lower one-third of the corn stalk can contain more than 5,000 parts per million nitrate-nitrogen, while the top one-third of the stalk and leaves contain less than 160 parts per million.
Roughly 6,000 to 10,000 parts per million of nitrate in feeds can create problems in unconditioned cattle.
Affected cattle will display mild clinical signs including pale membranes, depression, and slightly increased breathing, according to Wallace.
Once nitrate levels climb and more than 60 percent of the oxygen-carrying capacity is gone, most cattle will have very rapid breathing, have a wobbly gait, or be unable to rise, he said.
“Deaths are not uncommon without immediate treatment,” Wallace said, noting pregnant cows may abort.
Feed values. Producers should be sure to balance rations for lower levels of starch and reduced dry matter intake potential, cautions Mike Hutjens, a University of Illinois Extension dairy specialist.
The feed value of the corn silage is reduced 80 percent to 90 percent, depending on the amount of corn grain in the drought-stressed corn silage.
Barren stalks will feed similar to high-quality grass silage or hay, Wallace said.
Making corn forage as hay will be difficult, as the corn stalk will be wet (more than 70 percent moisture) and difficult to dry down.
Hay curing does not reduce nitrate levels. Fermenting corn silage reduces nitrate levels by 35 percent to 50 percent.
Testing for nitrates by a commercial lab is highly recommended after fermentation.
Silage? Before you decide to cut the corn crop for silage, determine ear development and stage of maturity, Hutjens said. Yields will depend on it.
If the corn plant has green tissue remaining, allow it to grow and mature, adding nutrients. Once the crop is to 30 percent to 40 percent dry matter, successful ensiling can be achieved.
Hutjens said your best bet is to add an inoculant.
If a sample of chopped corn silage is squeezed tightly in a grip and water runs out between fingers, the silage is over 70 percent moisture and too wet.
Running a dry matter test using a Koster tester, microwave, or commercial lab will be more accurate.
Setting your price. If your own crop isn’t looking so good for kernel yields, Hutjens suggested selling the crop to livestock producers as silage.
Based on the quality and tonnage in the field and adjusting for harvesting costs, a price can be calculated, he said.
Using a guideline of 1 ton (wet basis) per linear foot, 1 acre of corn silage standing at 5 feet (excluding the tassel) could provide 5 tons of wet corn silage times 30 percent dry matter or 1.5 tons of forage dry matter, he said.
Subtract harvesting costs (higher than normal for corn silage due to lower yields) or $8 per ton of wet corn silage or $40 an acre.
If the corn forage is worth $80 a ton of dry matter, the value per acre could be $120 per acre minus harvest costs of $40, he said.
The recommended approach is to weigh actual chopper boxes of silage and test the silage for quality to determine a price per ton and per acre.
Some grain producers may consider plowing down the corn stalks for fertility.
The nutrients in the corn stalks are estimated to be worth $25 per acre, Hutjens said.
Be sure to check with your local Farm Service Agency before making any changes to the crop.
(Reporter Andrea Myers welcomes reader feedback by phone at 1-800-837-3419, ext. 22, or by e-mail at amyers@farmanddairy.com.)

Simple test: Did your corn acreage pollinate?
COLUMBUS – There are two techniques commonly used to assess the success or failure of pollination.
One involves simply waiting until the developing ovules (kernels) appear as watery blisters (the “blister” stage of kernel development). This occurs about 10 days after fertilization.
Faster way. However, there is a quicker way to determine pollination success.
Each potential kernel has a silk attached to it. Once a pollen grain “lands” on an individual silk, it germinates and produces a pollen tube that grows the length of the silk to fertilize the ovule in 12 to 28 hours.
Within three days after a silk is pollinated and fertilization of the ovule is successful, the silk will detach from the developing kernel.
Unfertilized ovules will still have attached silks.
Silks turn brown and dry up after the fertilization process occurs. By carefully unwrapping the husk leaves from an ear and then gently shaking the ear, the silks from the fertilized ovules will drop off.
The proportion of fertilized ovules (future kernels) on an ear can be deduced by the proportion of silks dropping off the ear.
Silks can remain receptive to pollen up to 10 days after emergence.
Sampling. Sampling several ears at random throughout a field will provide an indication of the progress of pollination.
Unusually long silks that are still “fresh” are a symptom that pollination has not been successful.
Unpollinated silks continue to elongate for about 10 days after they emerge from the ear husks before they finally deteriorate rapidly.
During this period, silks become less receptive to pollen germination as they age and the rate of kernel set success decreases.
If you observe unusually long silks in a drought-stressed field, it may be an indication of pollination failure.
(Source: Peter Thomison, Ohio State crop specialist)

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