Producers who want to use the cover crops they planted last fall as supplemental feed for their livestock may want to harvest these crops quickly before the plants get too mature and the feed quality declines, says a forage expert from the College of Food, Agricultural, and Environmental Sciences at The Ohio State University.
Although cover crops are typically planted to control erosion and improve soil structure and health, they can also be a good option as supplemental forage for livestock, said Rory Lewandowski, agriculture and natural resources educator for Ohio State University Extension.
“There are a number of dairy farmers who take a cutting off of cover crops that are planted in the fall, like cereal rye and winter wheat, harvest it and use it as a wet forage, and then plant corn for silage,” Lewandowski said. “And warm-season cover crops including clovers, sudangrass, sorghum-sudangrass hybrids or spring-planted radishes used to promote soil health can also be grazed by livestock or mechanically harvested and used as stored forage”
However, while cover crops such as cereal rye, triticale and winter wheat can also be used as supplemental forage for livestock, they need to be harvested in a timely fashion for optimal use, he said.
“Cereal rye quality declines the most rapidly as the plant enters the reproductive growth stage, and it advances most rapidly from vegetative to reproductive growth compared to the other two forages,” Lewandowski said. “So producers should harvest these crops at boot to very early head stage of maturity.”
Producers should harvest these crops as silage or as wrapped forage as the best option for supplemental feed because there typically aren’t many good drying days during spring in the region, he said.
“Also, producers who choose to graze cattle on these cover crops should make sure they have enough animals to graze across the field before the crops get too mature and lose quality,” Lewandowski said. “It is also important to give livestock no more than one or two days’ worth of grazing at a time before moving the fence to provide access to another portion of the crops when using strip grazing.”
Producers also need to be aware that grazing on spring growth of winter wheat or cereal rye can increase the potential for grass tetany in livestock, particularly in cows still nursing calves less than four months old, he said.
“Grass tetany is a potentially fatal nutritional disorder in livestock caused by low blood magnesium levels,” Lewandowski said. “Grass tetany can be prevented by feeding animals that graze in lush, rapidly growing grass pastures a high-magnesium mineral mix starting at least a week or two before spring grazing and continuing throughout the spring grazing period.”
A free-choice high-magnesium mix should contain 12-15% magnesium from magnesium oxide and can be mixed with a grain or flavoring agent such as molasses to encourage cattle to eat it, he said. The mixture should be fed to cattle daily in 4-ounce portions throughout late spring until forages are more mature and temperatures are warmer, Lewandowski said.
Tetany is most likely to be seen in early spring grazing as cool-season grasses and small grains such as wheat and rye are most often low in magnesium and calcium and high in potassium, he said.
Signs of grass tetany include muscle twitching in the flank, muscular incoordination, grazing away from the herd, irritability, wide eyes, staring, staggering, collapse, thrashing and coma. It can quickly result in death.