Owens: ‘making corn silage great again’
By KAREN SCHWALLER
SUTHERLAND – While fermentation is as old as beer, Fred Owens said that few things have changed when it comes to making – and keeping – corn silage great.
Owens, professor emeritus from Oklahoma State University, said changes in corn silage since 1930 include hybrids and yields, plant health, harvest methods, the introduction of kernel processing, storage facilities (upright silos versus bunker silos), inoculants, feed-out methods and diets fed to livestock today, among other changes.
Of the options available for silage production, he said corn is “king.”
“Yield of digestible dry matter, protein and fiber per acre is greater for corn silage than any other field crop,” he said, “provided that soil fertility conditions, moisture availability, temperature conditions (50-90 degrees Fahrenheit) for plant growth, and season length are adequate.”
An important factor in corn silage “greatness” is choosing the right corn maturity for the local area, along with potential yield and types of plants that produce different hardness of kernels.
“The intended use of the crop should be considered,” Owens said. “If the crop (is) harvested as high moisture or dry grain rather than silage, dual-purpose hybrids are preferable so high grain potential and dry-down must be considered. If the crop is to be harvested as silage and fed, the maximum energy (grain) content is ideal. But the diet in which silage is to be fed also is relevant.”
He added that, for silage to be fed in high forage (dairy-type) diets, high fiber digestibility, along with possibly hybrids with the brown midrib (BMR) trait that leads to increased feed (energy) intake when fed with bulk diets, should be considered despite the weather risks associated with hybrids with the BMR trait.
“But when fed with high concentrate diets, maximum energy (grain) content of the silage is the primary factor of concern, not its fiber digestibility,” he said, adding that pesticide resistance and tolerance to herbicides, along with drought tolerance, should be considered in order to maintain high yields and plant health maintenance so harvest season can be extended if necessary.
While custom crew harvesting practices don’t necessarily allow for optimum timeliness for crops to mature, Owens said producers should pay attention to moisture content and the kernel milk line. He said dry matter content of field samples of corn silage range from 25 to 45 percent.
“Harvesting when the crop is too wet (under 30 percent) not only reduces yield, but also results in loss of fluids from the silage mass and produces very sour silage,” he said. “Cell contents, the most digestible portion of silage, are lost with effluent fields.”
At the other extreme, if the crop contains more than 40 percent dry matter when harvested, plant stem sections are not as easily chopped to a small size. Larger, longer particles are less flexible and less easily packed into storage to avoid spoilage during storage and feeding.
Owens said corn plants with up to 40 percent dry matter content will contain more digested energy, which is grain.
“Crowding this maximum moisture limit will increase energy value of silage, provided the crop remains green and healthy and can be readily chopped and packed into storage,” Owens said. “… but if plant diseases or frost kill the corn plants, the silage should be harvested as soon as possible.”
“Starch deposition in the grain can be monitored through checking the milk line of kernels,” he added. “The line between soft and hard sections of the corn kernels.”
Grain contains anywhere from 70 to 85 percent of the starch of mature kernels at the half milk line stage.
“If plants remain under 40 percent dry matter, delaying harvest until kernels are more mature increases the starch content of silage,” Owens said, “and because starch has over 1.5 times the energy value of leaves and stalks, energy value of silage increases because kernels continue to fill with starch.”
He added hard kernels have less digestible starch than softer kernels. Because of that, more mature silage with harder kernels should be kernel processed at harvest to reduce particle size of kernels. This helps maintain the high digestibility of grain in more mature corn silage.
“To soften the kernels and increase digestibility of starch, a lengthened storage time (up to three months) prior to feeding is also helpful, particularly when silage if fed in higher-roughage diets,” said Owens, adding that plant parts with digestible energy for cattle include, in order from greatest to least: grain, leaves, husk and shank, cob, top stalk, and bottom stalk.
“Consequently, high chopping will increase the digestible energy content of the harvested crop,” he said.
Compared to the digestible energy content of corn silage, grain (high moisture grain or dry grain), ear corn, earlage and snaplage (earlage plus some of the top stalk) will have increased available energy content because they contain higher proportions of more digestible plant segments.
“Placing the chopped forage rapidly into storage avoids crop heating and maintains the energy value of the crop,” said Owens, adding that packing promptly and properly is paramount for optimum storage and nutritional value.
Additionally, he said packing and covering with an oxygen barrier film directly following harvest avoids re-entry of air into the packed pile, and that high packing tractor weight and thin layering of added chopped material aids in high silage density. According to Owens, active inoculants can move fermentation along, especially for stressed crops or crops harvested out of season.
Air exposure should also be monitored during feed-out to prevent spoilage.
“Air exposure at the silage face and within piles of silage removed from storage allows yeasts present in the silage to grow and degrade lactate – a primary source of energy in silage – and will cause silage to heat,” said Owens. “Inoculating chopped plants at harvest with Lactobacillus buchneri inhibits yeast growth and reduces heating and energy loss of silage exposed to air.”
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