Cover crops expand forage options, but require management of potential nutritional and medical issues, according to Travis Meteer, University of Illinois Extension commercial agriculture beef educator.

Meteer described this year’s forage crop as “decent tonnage,” but anticipates a short supply of high-quality forage that will be felt more by dairymen than those with beef cattle.

Meteer recommended farmers first decide their method to harvest cover crops -- either grazing or harvesting for hay or silage. 

“The big thing is the variability (of cover crop nutrients),” Meteer said. “You need to have samples tested because cover crops are variable, and you need to balance rations. Summer annuals can be low in protein percentage-wise, compared to brassicas.”

Grazing may be a least-cost, low-labor option, but farmers must consider potential health factors, Meteer stressed.

If sorghum or sorghum-sudangrass is included, prussic acid can be a problem, especially with cool temperatures or frost. Meteer advised farmers to remove cattle before a frost and to keep them from the area for seven days after a killing frost.

Soil fertility levels also need to be considered to avoid nitrate poisoning. “Nitrate levels can be a concern if you’ve applied manure, or if you fertilized the field for corn and weren’t able to plant,” Meteer said. Likewise, droughty conditions in some parts of the state may result in high nitrate levels, he added.

Meteer recommended tissue testing of samples before the cover crops are grazed or harvested. Don’t allow animals to graze down to the bottom third of the plant and dilute the diet with low-nitrate, low-protein feed. Ensiling will remove about 50% of nitrates.

While fall cover crops, such as oats and brassicas, will appear lush, be aware those plants will be high in moisture content and not provide enough dry matter or energy, Meteer noted.

Animal “performance can be an issue because there is not enough dry matter or energy (in their diet),” Meteer said. “They can’t eat enough to sustain weight gain or for milk production.” Supplementing with grass hay or cornstalk bales can help. Adding a grain mix can also be beneficial.

Meteer advised farmers to transition livestock consumption of lush cover crops. “Make sure the cattle are full” when turned out into the cover crop and offer a consistent diet to avoid bloating problems, he said.

This year, some farmers are trying oat silage. Meteer noted grasses are low to moderate sources of protein and energy. He recommended supplementing the animals’ diet with distillers’ grain or even corn “at the right price.”

If harvesting for hay, such cover crops as millet and sorghum-sudangrass should be cut before setting seed, Meteer advised. Palatability becomes an issue when stems are rougher and plants are more mature.

Meteer also recommended monitoring how cattle consume cover crop hay. “What percentage of their body weight are they eating? Are they picking through it or just picking leaves?” he asked. “You could have issues with waste.”

Farmers may learn their supply estimates prove inaccurate. “They may be feeding more rapidly than you thought,” he said, meaning hay supplies would not last as long.

Despite the challenges, Illinois livestock farmers, especially with beef cattle, “have a tremendous opportunity to use cover crops as a base of forage and to use other Illinois co-products and corn,” Meteer said. “These things can give Illinois producers advantages compared to producers in other states.”

Illinois producers can maximize their opportunities and even use off-season crops “to take advantage of our high-quality soils and be competitive in the beef market,” Meteer concluded.