Farming Magazine - December, 2013


Forages: Winter Silo and Silage Management

By Everett D. Thomas

Photo by Nicholas A. Tonelli, CC-BY-2.0, via Wikimedia Commons.

By now all your forage has been harvested and ensiled, so you should be in good shape to begin the winter feeding season. Hopefully you haven't yet started feeding "new crop" corn silage. If possible, you should wait at least two months after ensiling to start feeding it, and with succeeding months the starch digestibility continues to increase.

Silage processing may boost the rate of increase in starch digestibility, but there's still good reason to delay feeding the new crop. The changes in starch (and also protein) digestibility aren't small; in fact, they're large enough that the corn silage you'll be feeding in early summer will almost certainly be more digestible than the silage you feed when you first open the silo, assuming that action takes place soon. The changes with time are large enough that in most cases they dwarf any differences between the various corn hybrids you planted, since variations in starch digestibility among hybrids are quite small.

A reasonable goal is to begin feeding new crop corn silage no earlier than January. Of course, this is difficult if not impossible in years when corn yields are below average. The real challenge is growing enough corn for silage in one year so that you have enough to feed through the end of the following calendar year. This would mean growing more corn than usual, but only for one year: After that it's no more difficult to produce enough corn silage for a "corn silage feeding year" that begins in January than if the feeding year began in October or November. Twelve months is 12 months.

Check silo covers

Now is a good time to check the condition of plastic silo covers and repair any holes or tears. If you find damaged plastic, some aerobic spoilage has already occurred, but you can limit further losses by repairing the holes with waterproof tape. Silage bags aren't immune to damage, and because silage density in bags is often less than in bunker silos or drive-over piles, the potential for serious losses is high.

Many years ago, a careless equipment operator put a three-cornered tear in the side of one of the silage bags at Miner Institute. We didn't notice it right away, but when we discovered it we thought we did a good job of patching the tear. However, it was too late to prevent serious silage losses. Before we got to that area of silage, we inserted a thermometer with a 15-inch probe next to the tear and watched the silage temperature climb to a worrying level. We had made silage, but where the damage resulted in air getting into the bag, the silage was turning into compost! We wound up throwing away over $100 worth of silage that could have been saved by pennies' worth of tape had we noticed the tear right away. A stitch in time ...

Now is also a good time to check where the silo plastic meets the sidewalls in bunker silos. Silage dry matter losses - unavoidable since they're part of the normal fermentation process - will result in some settling of the silage. Make sure the plastic is tight against the silo walls to prevent rainwater and snowmelt from running off the silo plastic and down the inside of the sidewalls. Recheck the plastic after a few weeks of fermentation. One of the best uses for the "gravel bags" that are becoming increasingly popular is to place a line of them along the walls of bunker silos, using a wide enough sheet of plastic to lap up onto the sidewall. Then the gravel bags are placed so as to prevent water from running between plastic and sidewall. Once filled with pea gravel, these bags are heavy enough to do the job, and if properly handled should last for many years.

Sampling silages

There are enough changes in quality between the day you ensile forage and when you start feeding it that you shouldn't rely on fresh forage analysis for ration formulation. However, fresh forage analysis will give you a good enough idea of quality that there shouldn't be any surprises when you start feeding the silage. NIR analysis - quick and inexpensive - is plenty good enough for this purpose. What you'll probably find is that the dry matter content of fresh forage is a percentage point or two higher than after the forage has fully fermented, while fiber concentration is a point or so lower. That's because the fermentation process involves heat, and you can't produce heat without an energy source. The main energy source in this case is plant sugars that are converted into lactic, acetic and other acids by silage bacteria, while the fibrous cell walls are affected to a much lesser extent.

Some years ago, I was about to give a presentation on forage quality at a large "Dairy Day" event when a dairy nutrition consultant approached me, asking if I would "please, please, please" say something about sampling silage through the sides of silage bags. I agreed, and what I said was this: There are several methods of sampling silage through the side of the bag, but none of them are recommended because in the process of sampling, the silage is exposed to air. Some have tried stuffing silage back into the hole; others have used salt. One year at Miner Institute we even tried filling the hole with caulking compound. What we found when we came to each of the sampling areas was caulking compound surrounded by a large amount of spoilage! If for some reason you absolutely must sample through the side of the bag, my suggestion would be to spray some acetic-propionic acid (the same material used to treat damp hay as it is baled) into the hole created by sampling, and then seal up the hole in the bag using the tape provided by the manufacturer and hope for the best. I'm not sure that this will work, but so far nothing else has worked worth a darn.

Ev Thomas has worked as an agronomist in New York for 45 years, first with Cornell University Cooperative Extension, then with the William H. Miner Agricultural Research Institute in Chazy, N.Y., including managing its 680-acre crop operation. He continues to work part-time for Miner Institute and is now an agronomist at Oak Point Agronomics. He has written our Forages column for 16 years and has been an expert contributor on a number of other topics.