By Hugo Ramirez Ramirez
With the limited hay crops in some areas this summer, beef producers may want to consider harvesting corn silage to supplement the cow herd this winter. Corn silage can be a very cost effective feedstuff for cow herds, but proper harvesting, storing and feeding is critical to maintain silage quality and feed value.
Dr. Hugo Ramirez Ramirez, Iowa State University dairy specialist, shared his top five priorities for making quality silage at the 2018 Iowa-Wisconsin Silage conference.
1. Harvest at the right moisture content.
During the fermentation process, sugar in the chopped corn is converted into lactic acid by bacteria, but the silage needs to be at 35% dry matter (or 65% moisture) to ensure it packs tight enough to become anaerobic so the bacteria can do their job. A ballpark indicator of whole plant moisture is the milkline on the kernel, harvesting at 2/3 to 3/4 milk line is a common practice to capture more energy as starch in the kernel. A better way to determine whole plant moisture is to actually chop up a few stalks and test it for moisture, either with a tester designed for this purpose or by using a microwave and kitchen scale. See instructions for testing silage moisture at https://store.extension.iastate.edu/product/5641.
A general rule of thumb is that corn plants will dry about 0.5% points each day.
2. Chop length and kernel processing. Good timely fermentation requires an anaerobic environment where the bacteria have access to the sugars and starch in the chopped corn plant. Particle size (and moisture) has a big impact on packing density and oxygen exclusion. When a kernel processor is used, particle size should be about 3/4”, and when a processor is not used the particles should be 1/4” to 1/2” in length. Kernel processing opens up the corn kernel which results in increased feed quality by allowing better energy utilization by the cow.
3. Inoculants. Bacteria are naturally occurring, but not all bacteria produce lactic acid to assist in the fermentation process. Adding a lactic acid-producing bacteria (LAB) to the chopped corn increases the "good" bacteria and speeds the fermentation process, resulting in less spoilage and higher feed quality. Inoculants are simply inactive live LAB which are activated when rehydrated, and because they are live bacteria, do not use chlorinated water to rehydrate the inoculant.
Packing to remove oxygen from the pile is critical since the bacteria require an anaerobic environment to ferment the forage. Density (pounds of forage per cubic foot) is used to measure the success of packing silage. Density is influenced by crop, chop length, dry matter, type of structure, delivery rate, packing weight and time. The target density for a bunker silo is 40-45 pounds of fresh forage or 14-16 pounds of dry matter per cubic foot. Density also has an impact on spoilage during feedout since a less-dense pile allows for more oxygen to enter the pile. A Wisconsin study showed that silage density of 16 pounds of dry matter per cubic foot had a 15% loss where 10 pounds of dry matter per cubic foot lost 20% of dry matter. A tool to help calculate the number of tractors needed to achieve adequate density based on silage moisture and delivery rate can be found at https://fyi.extension.wisc.edu/forage/2019-new-bunkdenscalc-7-21-11wporosity-russian-welsh/.
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