Corn and Soybean Management
Cutting Height and Corn Silage Production
by Greg Roth
During the last several years, interest has developed in increasing the cutting height of corn silage, in an effort to improve the quality of the silage. We conducted some field trials on the issue and many of our colleagues at other universities have as well. One of our faculty members in Dairy and Animal Science at Penn State, Dr. Zhiguo Wu, had conducted feeding trials with high chop corn while working at the USDA Dairy Forage Research Center. Over the past year, Dr. Wu and I have summarized the available information from both field and feeding studies on cutting height of corn silage. We have also visited with scientists and producers in the region on the issue. Based on this input we published a new factsheet entitled “Considerations in Managing Cutting Height of Corn Silage” available online on the Penn State Department of Dairy and Animal Science website at http://www.das.psu.edu/user/publications/pdf/das03-72.pdf. Copies can also be obtained by contacting Dr. Wu directly at 814-863-3669.
Based on 11 studies that we were able to locate, you can expect a loss of about 7% when raising the cutting height of corn silage by 12 inches. At the same time, the neutral detergent fiber (NDF) content of the silage in these studies was reduced from 41.6 to 38.6 % and the NDF digestibility increased from 50.6% to 54.0%. The dry matter of the silage increased by 2.2 percentage units, because the grain, which is concentrated in the high chop silage is the driest part of the corn crop.
We also summarized feeding trials that have been done on the issue. In two trials, when high chop corn was fed, milk production went up but milk fat went down, presumably due to the lower fiber content of the ration. From an economic perspective, given the higher cost of high chop corn, the lowered milk fat content in the milk offset the potential advantage of the higher production and the resulting impact was negative. In two other studies, rations were rebalanced when high chop corn was added and the amount of grain in the ration was reduced. In both studies, milk production was maintained on the lower grain, higher forage rations.
We used the information from the field studies we summarized to estimate the impact of the chop height on the cost of the rations. In our field study summary the high chop corn had an NEL of 0.74 compared to 0.71 for the conventional corn. Dr. Wu developed a sample ration and substituted in the higher chop corn in the ration and rebalanced it for the higher energy silage and reduced the grain in the ration by 5-6%. We accounted for the higher costs of the higher chop corn silage, based on the lower yield. This analysis indicated a potential savings of $0.07 per head per day, suggesting the practice could be profitable in some situations.
Is this a good practice for producers to adopt? That probably depends on farm specific factors. Reducing corn silage production on farms where the production potential is limited may not be a good idea. On farms where a significant amount of silage is fed to non-lactating animals, the potential economic benefit of the higher energy silage could be limited. On farms with silage storage capacity limitations, feeding 5-6% more silage could exacerbate the problem. Some producers have suggested to us that the tall corn stalks left in the field could end up in the rye harvested for silage the next year. Also, we know that hybrids will respond differently to the higher chop- and those with less than average responses would be less likely to result in an economic benefit.
On the positive side, we feel that high chop corn can be viewed as a tool to manage the dry matter and energy in silage. The dry matter issue could be important in some cases. Assuming that corn silage dries down at 0.5 percentage units per day, going to higher chop corn could allow a 4-5 day earlier start on harvesting. Given that it appears to be often a breakeven or possibly better proposition, this could be useful in some situations, such as working with a custom operator.
We suggest in the publication that producers estimate the potential of this practice under their own system, perhaps by using some of the approaches that we used in our factsheet and arrive at their own conclusions about the practice. For more details, obtain a copy of the factsheet from the website or Dr. Wu.
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