Those who use corn silage to feed cattle need to understand the basics of harvesting the crop as well as recommended storage and feeding practices. Correct silage management will assure a high-quality forage is available to livestock.
In a webinar Aug. 2, put on by the University of Nebraska-Lincoln (UNL) Extension, Hugo Ramirez-Ramirez, an Iowa State University Extension dairy specialist, spoke on the nuts and bolts of corn silage quality. Humans have been putting up silage for centuries, but the same old process does have some newer methods, he said.
THE 5 C'S OF CORN SILAGE QUALITY
Remembering the 5 Cs of corn silage quality can help those harvesting and storing the crop, Ramirez said. These include: content of dry matter, chop length, compaction of the silage, covering silage, and care and management at feeding.
"We need to think of corn silage as an investment and need to take care of it," Ramirez said. "Silage management equals risk management."
When to harvest silage is often a tough decision. Ramirez recommended looking at the dry matter (DM) content of the silage. Harvest should begin around 35% DM, with a range from 32% to 35%. The simplest way to determine this is to observe where the milk line is at, he said. The milk line marks the boundary between the liquid (milky) and solid (starchy) areas of the maturing corn kernels. Most experts recommend a good time to harvest corn for silage is when the milk line is about two-thirds to three-fourths of the distance from the dent to the kernel tip.
Some prefer to have silage with higher starch levels in the corn, so you would want to have slightly drier DM levels. The downside to this practice is that silage might not pack as well because of being drier, he said.
Once harvest does begin, the next important aspect to consider is chop length. To allow for good fermentation, it is necessary to remove as much oxygen as possible from silage. Small cuts of silage allow this: The length of cut for non-processed corn silage should be 1/4- to 1/2-inch and processed corn silage 3/4-inch. If silage length is too long, it becomes difficult to pack and could lead to spoilage and poor fermentation.
Another factor to consider when chopping silage is kernel processing. This unlocks the energy potential of the starch contained in corn kernels as the protective layer is damaged; it leaves the starch exposed for microbial fermentation in the rumen, he said."Milk production in dairy cattle and even feed conversion in beef cattle will both be higher by feeding corn silage harvested with kernel processing," he said.
Ramirez said kernel processing can be evaluated in the field by taking a sample in a 32-ounce cup and spreading out the sample. Sift through the sample and look at the kernels: The goal should be to have less than two half- to whole-sized kernels in the sample.
COMPACTION OF SILAGE CRITICAL
Compacting silage into a storage structure, whether it's an upright silo, bunker or pile, is an important process to assure corn silage quality. The objective of packing is to remove as much air as possible and create an anaerobic environment, he explained.
Density is a gauge to how well silage is packed, as this measures pounds of forage per cubic foot. Average density for a bunker silo is around 40-45 pounds of fresh forage per cubic foot if the crop is harvested at 35% DM, which is about 14 to 16 pounds of dry matter per cubic foot.
Ramirez said this is done by making sure the layers of the silage are 4 to 5 inches thick to assure good packing. Making the layers too thick will create air pockets, a no-no considering an oxygen-free environment is wanted.
After the silage is stored, an often overlooked step in storing silage is sealing and covering it.
Sealing ensures the anaerobic condition is met by preventing oxygen from entering the silage pile. In addition, covering the pile keeps rain from infiltrating and washing away some nutrients.
Spoilage, or the wasted silage, in uncovered silage piles can be as high as 25%, Ramirez said.
Plastic films with thickness of at least 4 millimeters are recommended, as they can withstand physical damage and also prevent or at least slow down the infiltration of oxygen. Some plastic film, called oxygen barriers, are thin films designed with high oxygen impermeability.
"Some studies have showed a 40% reduction of dry matter losses in the top 60 centimeters of covered silage piles," Ramirez said.
FEEDING IMPORTANT TOO
The last of the 5 Cs of corn silage quality is care and management at feeding time. The management of the silage pile's open face protects the surface area from oxygen, he said.
Ramirez said one important fact those feeding silage should remember is there can be some variability within the silage pile. Research has shown starch percentage DM can vary from 25% to 40% within the pile, he said.
He recommended those feeding silage should pull off some from the open face and pile it together to allow some mixing. This should make the starch percentage DM closer to 30% to 32%, he said.
Another recommendation is to pull more off the silage pile than you need to feed at one particular time. The silage now exposed to the conditions could lose quality before it's fed, he said.