It's that time of year when Mother Nature puts an end to the growing season. This year, it was done about on time with our average of Oct. 14, but sort of odd it went from 90 degrees to 50 degrees in a matter of a few days. The same thing happened last fall. Anyhow, I have been getting questions about livestock poisoning from frosted Johnsongrass and about the resting period for alfalfa prior to a killing frost.
I want to share a few timely reminders with you this week:
• Before a Frost (when temperatures are 33 degrees F and above)
Cool-season grasses, such as Tall Fescue and Orchardgrass, are regrowing with the cooler fall temperatures and rainfall. Ideally, these grasses should be utilized, but not over grazed into the ground (leave 3-4 inch residue height after grazing). Evaluate pastures for clover content and assess the risk for bloat as fall regrowth occurs (when pastures are greater than 65 percent clover).
• After a Non-Killing Frost (when temperatures are between 28 degrees F and 32 degrees F)
Do not graze summer annuals, such as sorghum x sudangrass or pastures with populations of Johnsongrass, for 2 weeks after a non-killing frost to reduce the threat of cyanide (prussic acid) poisoning. For more information on cyanide poisoning, refer to the UK publication ID-220 Cyanide Poisoning in Ruminants online or at our office.
• After a Killing Frost (when temperatures are below 28 degrees F for 2-3 hours or more)
Do not graze or cut alfalfa after Sept. 15 to allow adequate time for plants to replenish root reserves and prepare for winter. Cattle can be turned back into an alfalfa stand for grazing after a killing frost. This should be done within 3-5 days since alfalfa quality declines rapidly after freezing and plant material degrades quickly. Make sure fields are not too wet or cattle hoof traffic will damage alfalfa crowns and also create a bumpy mess to drive over next year.
Cool-season grasses will not grow much until the next spring after a killing frost, so during this time either use that forage by grazing it down short, or you will lose it.
Do not graze summer annuals, such as sorghum x sudangrass or pastures with populations of Johnsongrass after a killing frost until the plant material is completely dry and turned brown. Make sure the base of the plants are dead and not still green.
Generally, cattle can be turned into stockpiled tall fescue pasture after November 1 after other pastures have been grazed. For best results use the strip grazing method where temporary fence is used to provide a small portion of the pasture at a time. Ideally each strip should supply the herd enough forage for 2-3 days before being moved. Stockpiled fescue usually yields 1-1.5 tons/ac. which will carry one cow for 50-75 days.
• Making Hay With Johnsongrass-Best Use Now
During this time of repeated light to heavy frosts, probably the best use of Johnsongrass is to harvest it as hay. If it is frosted either before or after cutting, the toxic compounds will dissipate during the days required for dry down. Let hay dry as long as possible to give even more time for cyanide to leave the plants. Once made into a bale, cyanide will also continue to dissipate over time.
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