Fall grazing offers opportunities, challenges
September 21, 2017
After a summer of drought in North Dakota, pastures have been used heavily and cattle producers are looking for forage options to get them through the fall.
"In areas that have received late-summer rains, producers may be able to benefit from green-up of pastures and hay land, regrowth from cereal and annual forages cut for hay, or crop volunteer regrowth," says Janna Kincheloe, the North Dakota State University Extension Service's area livestock systems specialist at the Hettinger Research Extension Center. "It is important to consider grazing management and potential plant and animal health implications when developing options for fall forage opportunities."
John Dhuyvetter, NDSU Extension area livestock systems specialist at the North Central Research Extension Center near Minot, adds "With continued moisture stress, and anticipated cooler temperatures and possible frosts, there are concerns with potential toxicities and transitioning cattle from a dry, fibrous mature plant diet to highly digestible immature regrowth."
One such concern is nitrate accumulation in regrowth of annual forage crops. Plants are immature and high in nitrogen. Clipping a representative sample and testing the crop prior to livestock turnout can provide an indication of nitrate levels and potential toxicity at a point in time.
“It is important to consider grazing management and potential plant and animal health implications when developing options for fall forage opportunities.” Janna Kincheloe, livestock systems specialist
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Prussic acid also can accumulate in several crops such as sorghum and sorghum-sudan grass crosses. The specialists recommend that producers avoid allowing their cattle to graze on these crops for at least seven to 10 days after a killing frost to let the plants dry.
If conditions allow for regrowth after a frost, new shoots and leaves also are likely to be very high in prussic acid. Feeding these crops as green chop, silage or hay instead of allowing animals to graze them can reduce the risk of prussic acid poisoning.
"Bloat also can be an issue anytime that cattle have an opportunity to consume large quantities of immature, highly digestible forage, particularly in pastures that are made up of 50 percent or more of legumes such as alfalfa or clover," Kincheloe says. "Volunteer canola also carries risk of bloat."
The incidence of bloat tends to be greater early in the day, following a rain or after a frost. Best management practices include turning cattle into regrowth in midday after they've been grazing elsewhere and after a full feed of dry hay.
"If possible, provide access to other grazing, such as a permanent pasture, simultaneously," Dhuyvetter suggests. "Providing a poloxalene block prior to and during grazing and placing hay bales in the field for grazing are additional management considerations."
If volunteer grains matured to seed formation or abandoned areas of the field have mature grain, grain overload from selective grazing could be a problem. High grain intake by cattle not adapted to grain can lead to bloat, founder or death. To manage these issues, producers should use strip grazing to limit access and/or adapt cattle to grain a week or so prior to grazing.
Kevin Sedivec, NDSU Extension rangeland management specialist, recommends that producers thinking of extending the grazing season into the fall on native range should try to use pastures that were deferred or lightly grazed during the growing season. Defoliation of plants at this time may limit the ability of the plants to store energy through the winter, which can impact forage production next spring.
"If producers have no choice but to graze native pastures, they should try to maintain an adequate stubble height (typically 50 percent of ungrazed mature plant height or 4 to 6 inches, depending on plant species) and stock pastures lightly," Sedivec says. "Pastures grazed late in the fall should not be used immediately during the following spring."
Regardless of what type of grazing a producer is considering, providing adequate salt and mineral is a good idea, according to the specialists. With rapid regrowth of cool-season forage, magnesium supplementation may be necessary to help cattle avoid grass tetany.
"A variety of options are available for extending the grazing season into the fall and making efficient use of available resources," Dhuyvetter states. "This can be particularly beneficial in getting calves to traditional weaning at good weights and putting some weight back on cows. With testing, avoiding turning hungry cows into unfamiliar feed and closely managing grazing, these opportunities can be managed successfully."