John­songrass Mer­its Con­cern

McDonald County Press - - AGRICULTURE -

MOUNT VER­NON — The last two or three years, in­quiries about john­songrass risks have been in­creas­ing in south­west Mis­souri, ac­cord­ing to El­don Cole, live­stock spe­cial­ist, Uni­ver­sity of Mis­souri Ex­ten­sion.

“Fa­vor­able grow­ing con­di­tions have re­sulted in john­songrass spread­ing at a rapid rate,” said Cole. “John­songrass has been on the Mis­souri nox­ious weed list as long as I can re­mem­ber.

Ac­cord­ing to Cole, john­songrass is more of a con­cern for row crop farm­ers. How­ever, ef­fec­tive her­bi­cides help row crop farm­ers hold it in check.

“We have cau­tioned live­stock own­ers for years of the risks as­so­ci­ated with the for­age, whether grazed or put up as hay,” said Cole.

Those risks are prus­sic acid or cyanide poi­son­ing and ni­trate. Each may re­sult in an­i­mal death if not caught in the early stages.

“In re­al­ity, we’ve not seen or heard of very many pos­i­tively di­ag­nosed in­stances of cat­tle death from john­songrass as farm­ers have learned to man­age it,” said Cole.

Ac­cord­ing to Cole, cat­tle seem to like it, es­pe­cially when grazed in a ten­der, palat­able leafy stage of growth.

From a graz­ing stand­point, Cole says to wait un­til john­songrass is 18 to 24 inches tall. The prus­sic acid risk is great­est un­der that height when naive cat­tle are hun­gry and are turned into a pas­ture with a good bit of john­songrass in it.

“If you al­low cat­tle to graze john­songrass as it grows from early spring, they sel­dom have prob­lems. Drought stress may fa­vor a prus­sic acid risk,” said Cole.

Un­der graz­ing sit­u­a­tions, if live­stock pro­duc­ers want to be less risky when turn­ing into a john­songrass field, only turn one or two lower value an­i­mals in as mon­i­tors.

“If they’re still alive af­ter 30 to 45 min­utes, the grass is prob­a­bly safe for the rest of the herd. It might also be of value to have your vet­eri­nar­ian on speed-dial at turn-in time. If caught quickly, they may save the an­i­mal,” said Cole.

The prus­sic acid con­cern is rarely a prob­lem with hay as it leaves the plant soon af­ter it is cut.

“There is not a re­li­able field test that is widely used by ex­ten­sion spe­cial­ists, but some vet­eri­nary clin­ics may use a test kit, but it needs to be done where the john­songrass is at,” said Cole.

Feeds other than john­songrass — such as shat­ter­cane, sorghum-su­dans, wild black cherry trees and sorghums — all may have the abil­ity to cause prus­sic acid poi­son­ing. Cat­tle, sheep and goats seem more sus­cep­ti­ble.

John­songrass can ac­cu­mu­late ni­trates, es­pe­cially dur­ing drought and when high amounts of com­mer­cial fer­til­izer or an­i­mal ma­nure are ap­plied. MU Ex­ten­sion of­fices and for­age test­ing labs can check plants for that risk.

Un­for­tu­nately, ni­trates do not re­duce in quan­tity in dry hay. Ni­trates can be lethal but prob­a­bly are more likely to re­duce milk pro­duc­tion, cause abor­tions and lower growth rate.

“Ve­teri­nar­i­ans can more ac­cu­rately di­ag­nose ni­trate poi­son­ing than prus­sic-acid death. The blood will be a choco­late brown, whereas prus­sic-acid poi­son­ing blood will be a bright, cherry red. If large amounts of ni­trate con­tain­ing for­age are eaten, death can oc­cur in a few min­utes,” said Cole.

For more in­for­ma­tion con­tact El­don Cole in Lawrence County, (417) 466-3102 or any of th­ese MU Ex­ten­sion agron­omy spe­cial­ists in south­west Mis­souri: Tim Sch­naken­berg in Stone County, (417) 357-6812; Jill Scheidt in Bar­ton County, (417) 682-3579 and Sarah Kenyon in How­ell County, (417) 256-2391.

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