Corn Silage: Part 3 Signs of Proper Processing, Packing, and Storage Plus Safety Tips

Proper processing, packing, and storage will help ensure a quality feed for cattle and minimize feed losses. In this podcast episode, University of Wisconsin specialists give recommendations you can use out in the field and as you store your crop. Also in this episode are great tips to help keep you safe this harvest season.


Liz Binversie, Brown County UW-Extension Agriculture Educator


Brian Holmes, PhD, Emeritus Professor, Biological Systems Engineering Department, UW-Madison/UW-Extension

Randy Shaver, PhD, Dairy Nutrition Specialist, UW-Madison/UW-Extension

John Shutske, PhD, Agricultural Engineering Specialist, UW-Madison/UW-Extension


Time: 10:29 minutes


Liz Binversie: Greetings, I’m Liz Binversie, Brown County Agriculture Educator for UW-Extension and I’ll be your moderator for today. On the panel is Brian Holmes, Emeritus Professor in the Biological Systems Engineering department at UW-Madison; Randy Shaver, Dairy nutrition specialist for UW-Madison & UW-Extension; and John Shutske, Agricultural Engineering Specialist for UW-Madison & UW-Extension.

Proper processing and storage are key to ensuring a high quality feed for dairy and other livestock. Today we will discuss ways you can tell how well you’re doing with processing, packing, and covering. Brian, could you tell us more about how producers can gauge how well they’re doing?

Brian Holmes: Well, people need to understand that oxygen is the enemy of silage. The following recommended practices help to minimize exposure during the filling process and during storage. First of all, you want to fill the silo as quickly as possible—preferably less than a week. Cover the top forage with plastic if filling must be temporarily interrupted due to rain or some other method of slowing down your harvest. Line the walls with plastic, leaving at least 3 feet of plastic to extend over the tops of the walls. Then, proper packing is important to exclude oxygen from the forage mass prior to fermentation and to minimize the porosity of the silage produced. Porosity is a measure of the space between the forage particles. When the silo is open during feed out, high porosity silage allows oxygen to penetrate the silage quickly and to a greater depth than does low porosity silage. This exposes the silage to aerobic deterioration at a very high rate. Good packing is characterized by high density, low porosity silage. There have been several attempts to determine if forage is packed well enough while the packing processing is going on, but I haven’t heard of anybody that has developed a successful method of doing this. There is a spreadsheet available that’s been developed to help predict if the packing process is likely to achieve or exceed the recommended density of greater than 44 pounds of as fed silage per cubic foot and a porosity of less than 40%. This spreadsheet is available on the UW-Extension Team Forage harvesting and storage website. The spreadsheet allows a producer to enter harvest rate, forage depth, packing layer thickness, number of packing tractors, and the weight of each packing tractor. This spreadsheet calculates an estimated density and a porosity you’re likely to achieve. The nice thing about using a spreadsheet is that you can change some of the variables related to the packing process to see what the effect is going to be and make changes in the spreadsheet rather than actually making them in the field. Once you’ve got your silage properly packed, cover the forage with plastic as soon as the silo is full. Overlap the plastic at the joints by at least 3 feet, weight the plastic so it comes in complete contact with the forage using tires or tire sidewalls that touch each other or by using tarps and gravel-filled bags spaced at about 10 foot intervals. Place extra weight at the joints, and on silage piles seal the plastic on the ground surface with sand or gravel strip. Randy, kernel processing is an important procedure to make sure you have efficient digestion of corn starch. Tell us how to achieve a good kernel fracture on your chopper.

Randy Shaver: Thanks, Brian. I’d like to separate this into in the field—so as we’re chopping to ensure that we are getting good processing—and also coming out of the silo. In the field, I would refer you to the Team Forage website where there’s a really nice publication put together by Kevin Shinners and Brian Holmes from the BSE (Biological Systems Engineering) department here at Madison. It really is based on a hydrodynamic or a buoyancy separation of the kernels from the stover. Essentially, you would take some of that fresh-chopped silage, put it in a pail of water, allow that to separate, and then with your hands, take the stover portion off the top because that floated. Then you can pour out the water and you’ll find the kernels. Then you can simply look at those kernels and you would like to have all of those kernels broken. You would prefer to see those either in quarters or 1/8 kernels to ensure good kernel breakage at the time of chopping. Some people will simply take the silage and kind of separate it out and try to make sure they don’t have any whole kernels, but I find this water separation or flotation procedure to really be very effective on a fresh-chopped sample. It can allow you to then either chop finer or simply tighten down the rolls and make sure you’re doing a better job with processing. As we’re feeding out the silage, from the bunker then we have a laboratory procedure where we can take the sample, send it into a commercial testing lab, and they will run kernel processing score. A score or an index of above 70 would indicate excellent processing and high starch digestibility. A score or index less than 50 would indicate poor processing and would indicate we may need to feed more grain to try to get better performance. Those are really the two methods: in the field—kind of a hydrodynamic separation to really look at kernel breakage—and then coming out of the silo—we can do more of a quantitative assessment. With that, I’d like to refer to John Shutske and have him bring in some of the safety issues related to the harvest.

John Shutske: Alright, thank you, Randy. When you’re putting up silage into any kind of structure, it’s a complicated job and it’s also potentially pretty dangerous. We can’t cover everything in a short time so I want to point you to a website: I’ll highlight just a couple things here. First thing I want to talk about is silo gas. Silo gas is also known as nitrogen dioxide. It’s a really crucial part of making silage. It’s natural. We start to see this gas just about maybe 6-18 hours after a silo has been freshly filled. That can include not only a tower silo but a bunker or a bag as well. After it’s produced, it generally hangs around for about 2-3 weeks, depending on the conditions. The biggest problem is when you find silo gas in a confined space, especially in a tower silo. Silo gas is irritating—even a few breaths can cause serious health problems—so we really do encourage people to avoid silo gas, especially during that initial 3-week window. Treat a tower silo, especially, as a confined space, ventilate it thoroughly—generally with a blower, and get other types of information that you might need, especially if you have hired workers. Entering a confined space incorrectly can have deadly consequences. There’s some others hazards that I want to talk about. One is connected to tractor rollovers that happen every season while people are packing bunkers and piles. It’s critical—first of all—to make sure that you’re working with the right tractor. The right tractor obviously has a rollover protective structure and a seat belt. A wide front end on a tractor that you’re using for packing is also an absolute necessity. Front wheel and front wheel assist tractors can provide extra stability and traction for packing and duals are also used very commonly and they can increase stability, as well as appropriately placed weights. When you’re packing silo, make sure you back up any slope—or at least that’s strongly preferred—to increase your stability and your control. On slopes as you fill a bunker, make sure that you’re packing surfaces are not too steep. We generally talk about a safe slope being about a 3 to 1 slope or something even less steep than that. If you have a pile or a bunker that’s 20 feet high or 18 feet high—but let’s just use 20 to make the math easy—you need a horizontal direction run of about 60 feet—or about 20 times 3—to achieve that safe slope. Anything less than that, and you run a great chance of rolling over a tractor. There’s several other precautions to take with your employees and family members who might be working with you at this time. Some of them are to make sure to only hire experienced people, and make sure that they know how to operate the equipment. Require equipment operators to remain inside their vehicles to avoid being run over. Certainly you want to make sure to keep children and visitors out of the work zone.

Liz Binversie: Thank you to our wonderful panel today. If you would like to reach any of our specialists, you can do so by email. Tune in next time as we discuss how to stay safe this harvest season.