Dry Summer Makes Some Forages High Risk for Livestock

Dry weather and unusual growing conditions create a number of concerns for livestock producers according to Eldon Cole, livestock specialist with University of Missouri Extension.

For example, southwest Missouri had a large acreage of corn planted this spring but cool wet weather followed by hot, dry conditions resulted in corn only three to four feet tall that is tasseling and drying up.

Farmers are also calling county extension offices seeking options and asking if nitrate levels are high enough to cause problems.

Testing

“Most extension centers will test corn or sudan forages for nitrates. It is a subjective test based on color change after a solution is placed on the cut surface of fresh stems,” said Cole. “We like to check several stems or stalks to get a representative feel for what risk the field may hold.”

Stunted forages from fields that had high commercial nitrogen levels or animal manures applied have the greatest risk factor according to Cole. A wide variety of plants accumulate nitrates including cool season grasses, bermudagrass, millet and certain weeds like johnsongrass, pigweed and lambsquarter are known accumulators of nitrates.

The “quick test” for nitrates is subjective. Any indication of risky nitrate levels should be followed up with a forage testing lab’s quantitative test ($10 or less) to more accurately assess the risk and feeding practices recommended for its use.

Nitrate Levels
Nitrate levels are reduced from 25 to 50 percent when forages are harvested as silage or haylage whether in a silo or wrapped in plastic.

A dry-weather, stunted corn stalk
shows a high level of nitrates

“It is possible for the forage to lose that much and still be capable of causing poor performance, abortions and even death if the initial level of nitrate was really high,” said Cole. “Forages put up as dry hay do not show the lowered toxicity seen in silage.”

Dilution of silage and hay with non-nitrate bearing feeds can help cattle cope with the high nitrate forage. If the high nitrate forage is to be grazed, dilution is a bit more difficult.

“The option is to limit grazing time each day based on the lab’s nitrate level results. Also, try to allow the animals to only graze the top half of the plants as the leaves will run lower in nitrate than the stems,” said Cole.

Should the forage receive a rain on it before harvest, Cole recommends waiting five or so days before cutting or grazing it because the rain may allow the plant to temporarily accumulate higher levels of nitrate.

There are some who ask if there’s a time of day that might be better to cut hay that could contain nitrates. A number of nitrate tests were made in Oklahoma on forage sorghum cut from 8 a.m. to 6 p.m. The time of day did not affect the nitrate levels in the resulting hay.

“Nitrates in forages can be scary because they can result in death. However, awareness testing and suitable management can help salvage a high risk crop,” said Cole.

For more information, contact any MU Extension agronomy specialist in Missouri.

(By David Burton, MU Extension)