By Scout Nelson
This fall, southern rust has left visible marks on Nebraska corn fields, raising concerns about how it may influence livestock grazing after harvest. Southern rust (Puccinia polysora) is a fungal disease that forms lesions on corn leaves, weakening plants, and causing early leaf senescence. As leaves die prematurely, nutrients are transferred to the grain, reducing both leaf quality and quantity.
For livestock grazing corn residue, this means less available leaf material—the primary component of residue-based diets. Additionally, with tissue damage and earlier senescence, leaves decompose more rapidly, shortening the period of high-quality grazing.
However, there is one reassuring factor: “Southern rust requires actively growing tissue to survive, so it won’t overwinter in residue.” This means no risk of spreading the disease through grazing or feeding infected material.
Monitoring residue quality is essential. Adjusting stocking rates and grazing duration helps maintain livestock performance when residue availability and quality decline due to rust or early plant death.
In addition to corn, grain sorghum residue can serve as valuable feed for mid- to late gestation cattle. Research shows that severe leaf diseases may increase fiber content and reduce digestibility by over 10%.
Despite this, both corn and sorghum residues provide good post-harvest nutrition if managed properly. Corn residue should be grazed first, as leaves detach within one to two months after harvest. Sorghum leaves, by contrast, remain attached longer, offering extended nutritional value through winter.
Grazing management should consider potential toxicity risks. Sorghum stover can develop prussic acid after frost; waiting at least seven days after a killing freeze reduces this risk. Drought-stressed sorghum may also accumulate nitrates, so providing hay or supplements before turnout helps protect cattle's health.
For more crop residue grazing guidance, resources are available through CropWatch and UNL Beef.
Photo Credit:gettyimages-eugenesergeev
Categories: Nebraska, Crops, Corn, Sorghum, Livestock, Beef Cattle, Dairy Cattle, Weather