REDFIELD, Iowa (DTN) -- With harvest in full swing, cattle producers are anxiously awaiting turning out their livestock on cornfields for residue grazing to help extend the time needed before needing to use stored winter feedstuffs.

Mary Drewnoski, a University of Nebraska beef systems specialist, said the amount of time cattle can graze on cornstalks depends on the yield in the field. She said this during a webinar hosted by the Iowa Beef Center recently. "We like to look at it as one cow can graze for one month for every 100 bushels of corn grain taken off the field," she explained. "And we target 50% use of the leaf and husk, which is about 40% of the residue, but a lot of that is unsuitable for the cow to utilize."

For example, if the field is 160 acres and makes 250 bushels per acre and the producer has 150 cows, the math is 250 bpa per 100 bushels of corn equals 2.5 cow months per acre. "If you have 160 acres times 2.5 cow months per acre that equals 400 cow months. Then divide that by 150 cows and you would have 2.7 months of grazing or 81 days of grazing on average for a 1,300-pound cow," she explained.

KNOW WHAT IS AVAILABLE

Drewnoski said the amount of corn stover doesn't necessarily always increase based on yield and if the yield is extremely high, there can be a decrease in residue, but the general rule usually will apply. Having a conservative estimate of available grazing time based on yield is a good place to start when it comes to determining stocking rates in a field.

"Forty pounds of residue is the average amount of residue that we'd expect per bushel of corn grain produced. Corn grain is 56 pounds per bushel, but there is a lot of residue per bushel that's being produced and about 40% of that, or 16 pounds, is husk and leaf," she said.