For release: Aug. 26, 2004
Contact: Alvaro Garcia, (605) 688-5488

Cutting height affects corn silage

BROOKINGS, S.D. – Changing weather this year has affected corn silage maturity and potential harvest dates across eastern South Dakota. There might be concerns about the nitrate content of corn plants at harvest time, South Dakota State University Extension Dairy Specialist Alvaro Garcia said.

“One option for producers is to decrease nitrate content is to increase cutting height of corn harvested for silage, as most of the nitrate is concentrated in the stalk. Increasing cutting height, although reducing total forage yield, results in higher quality silage with greater response in milk production,” Garcia said.

Results of a recent trial conducted at the USDA research center in Madison, Wis., (ADSA, 2004) evaluated the performance of dairy cows fed corn silage harvested at two different cutting heights. Corn silage was cut at 8 inches (normal cut) and 24 inches (high cut).

The silage was chopped at 0.4 inches of theoretical length of cut and ensiled in silo bags. Cows in the trial were averaging 70 days in milk and producing 99 pounds of milk per day. Total mixed diets were formulated to contain 65 percent forage, of which 70 percent was corn silage and 30 percent alfalfa silage.

Increasing cutting height reduced total silage dry matter yield by 8.3 percent, increased grain content by 11.6 percent and decreased stalks by 38.5 percent. The concentration of dry matter, protein, and starch increased 9.1, 4.8 and 22.3 percent with the high cut silage, and the fiber fractions and lignin were reduced.
Although the dry matter intake was similar between the normal and the high cut corn silage diets (53.7 and 54.1 pounds per day), the high cut silage diet increased milk yield and 3.5 percent fat corrected milk compared to the normal cut diet (88.9 versus 86.5 and 91.5 versus 89.8 pounds per day, respectively). Feed efficiency (pounds of feed intake per pound of milk produced) increased with the high cut treatment (1.66 versus 1.62).

“Cutting corn silage higher, although reducing total forage yield by 8 percent, resulted in increased total milk and fat corrected milk production, and improved efficiency of feed utilization,” Garcia said. “Leaving 16 additional inches of corn stalks in the field can be an additional advantage when dealing with corn plants where nitrate concentrations might pose a problem.”

Garcia added that although research has demonstrated that nitrate concentration is reduced through fermentation in the silage, SDSU nevertheless recommends that producers test their corn silage for nitrates before feeding it to the cattle.

More about dealing with nitrates is included in SDSU Extension Extra 4017, Harvesting and Feeding Drought-Stressed Corn.” Find it in pdf format the SDSU Extension Drought/Climate Stress Web site, http://sdces.sdstate.edu/drought/. Under “Highlights” at the left hand side of the page, click on “Nitrates.”

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