September 10, 2003

 

Can You Afford to Raise Corn Silage Cutter Height?

Corn silage, where available, is the forage of choice for most dairies. One management technique some producers are considering is to cut corn higher to reduce fiber concentrations and increase fiber digestibility and energy content. The costs of that technique may outweigh the benefits, says J.W. Schroeder, North Dakota State University Extension Service dairy specialist.

"In theory, increasing the cutting height of the corn for silage at harvest to improve its quality would reduce fiber concentrations and increase fiber digestibility and energy content of the silage which should support high milk yield," he says. "But generally, the reduction in yield is too large and the improvement in cow performance is too small to make the technique pencil out."

Research in Wisconsin shows that increasing cutting height from 5 to 18 inches decreased dry matter yield by 15 percent, but the increased nutrient content should support greater milk yield based on the projections of their Milk2000 model developed to evaluate forge varieties. University of Delaware researchers reported that silage produced from leafy hybrids harvested at either 5 or 18 inches had similar improvements in silage quality, but actual milk yield was also similar for cows fed diets containing silage harvested at either 5 or 18 inches.

More recently, Georgia researchers harvested two corn varieties when the milk line in kernels was two-thirds of the way to the tip of the kernal at a cutting height of 4 and 12 inches. The corn silage harvested at 12 inches had lower concentrations of neutral detergent fiber and was more digestible based on laboratory dry matter digestibility content compared to the corn silage harvested at 4 inches. The corn silage was fed to lactating cows in a seven-week study. However, dry matter intake, milk yield, and milk composition was not effected by the cutting height.

"These results do not support increasing the cutting height for harvesting corn silage as a means of improving milk yield under normal situations," Schroeder says. "The decreased corn silage yield would increase the cost per ton of silage harvested by 10 to 15 percent. If corn silage provided 40 percent of the dietary dry matter in the diet, an increase of at least one pound of milk per day would have been required to break even at a cost of $35 per ton corn silage (normal cut) considering a 10 percent reduction in corn silage yield and a milk price of $10 per 100 pounds."

There are times when the cutting height should be increased, Schroeder notes. "It is well known that increasing the cutting height reduces nitrate concentrations in the resulting silage when nitrate toxicity is a possibility. That’s because the lower portion of the corn stalk has higher concentrations of nitrate."

"While increasing the cutting height does not appear to be a viable means of increasing milk yield, there are greater potential gains that can be made through kernel processing, increasing packing density, covering the silage, and managing the silage face," Schroeder says. "These not only can improve milk yield, but reduce the amount of secondary fermentation and waste silage."

Once in the bunker, proper management of the silo face is important to help maximize performance and profitability. Silage that is exposed to oxygen prematurely can heat and mold, Schroeder notes. This feed has a lower nutritive value for cattle and can decrease feed intake and performance.

Important concepts to remember are:

• Silage should be removed from a bunker or pile by trimming the pile from the top to the bottom with the loader bucket. Lifting silage with a bucket starting at the bottom of the pile causes fractures in the silage, allowing oxygen to enter. This leads to a premature heating of the silage.
• The surface of piles should be kept clean, with no extra feed loosely piled in front of the silo face.
• Especially during the summer and early fall, 6 inches should be removed daily from the silo face. With upright silos, at least 4 inches should be removed daily. During the coldest parts of the year, these amounts can be decreased slightly, to 3 or 4 inches removed daily.

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Source: J.W. Schroeder, (701) 231-7663, jschroed@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu