WOOSTER, Ohio — Producers who want to use the cover crops they planted last fall as supplemental feed for their livestock need to harvest these crops quickly before the plants get too mature and the feed quality declines.
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, OSU Extension agriculture and natural resources educator in Wayne County.
“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.
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. Lewandowski 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.
Producers should harvest these crops at boot to very early head stage of maturity, he said. 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.
Grass tetany warning
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 percent 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.
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