Summer annuals such as sorghum/sudan, sundangrass, pearl millet and johnsongrass provide excellent grazing and tremendous tonnage. While a valued forage alternative it does come with limitations and problems. Producers should focus on two issues – 1) late summer toxicities, nitrates and prussic acid 2) stockpiling to extend the grazing season.Although these summer grasses provide a quick first cutting and have good yield potential, problems can exist with cyanide and/or nitrate poisoning.
Prussic acid, or cyanide poisoning can occur when grazing sudangrasses, sorghum x sudangrass hybrids and johnsongrass following a frost. Extension recommends not grazing any of the sudan or sorghum-sudan crosses (including johnsongrass) for two weeks after a frost. The cyanide will dissipate during this time. Any frosts during this waiting period can cause the release of more prussic acid, causing the waiting period to be extended.
Another concern of summer annual grasses are the danger they pose due to nitrate poisoning. High Nitrogen rates, followed by extreme drought or cloudy cool weather is the perfect environment for nitrate poisoning. The toxin accumulates in the stalk and lower portion of the plant, and remains in the hay made from these plants.
It’s always a good idea to have plants tested for nitrates. Obtain plants from throughout the field and drop by the Extension Office. A simple acid screening test will reveal the presence of nitrates. Further testing may be needed in those cases where the screening is positive.
The recent moisture was a blessing for livestock producers across the state. One way to extend the grazing season is to stockpile tall fescue in the fall. One of the greatest expenses for a cow/calf operation is the winter feed cost. Stockpiling the fall growth of tall fescue is a way to lengthen the fall grazing season and reduce winter feed costs. Stockpiling means setting aside up to one acre per cow in early September, fertilizing with 180 lb ammonium nitrate per acre then letting it grow until after frost. For fields that weren’t fertilized in spring, potash and phosphate can be added at the same time to correct any nutrient deficiencies. This growth can then be grazed during the remainder of the fall and into the winter. Forage produced by tall fescue in the fall does not drop in quality as fast as forage produced in spring. Research has shown that the forage can stay above 10 percent crude protein all the way into February. With normal rainfall, stockpiling can add an extra two months to the grazing season, for about half the cost of hay.
For more information on grazing or forage tips, contact the Cannon County Extension Office at 563-2554. Information is also available on the web at http://forages.tennessee.edu/.
