Corn silage quality was improved with the invention of silage processors, while recently developed harvest technologies may result in forage that's even more highly digestible by dairy cows and other ruminants.
Photo courtesy of Miner Institute.
In the past year, farmers have been introduced to some new forage harvest equipment, as well as information about how to better use and manage harvest equipment that's been on the market for years. This article will focus on what we've been learning about the "care and feeding" of both old and new forage harvest equipment.
Processed corn silage
Processed corn silage is great forage, with higher starch availability and less feed bunk sorting and refusal compared to unprocessed corn silage. However, if you're going to chop corn that is below 30 percent dry matter (DM), processing the crop might end up doing more harm than good. That's because of higher effluent losses when immature corn silage is processed.
A Washington State University (WSU) study looked at the effects of processing very immature corn - 23 percent DM. The researchers found that over a three-month period, processing this crop increased effluent losses by 60 percent, to almost 20 gallons of effluent per ton of silage. Consider how much "silage juice" this is for a 1,000-ton silo: almost 20,000 gallons of effluent! Also consider the damage this amount of effluent could do to a vegetated filter system. Silage effluent contains a lot of soluble nutrients. In the WSU study, 19 gallons of effluent contained about 5 pounds of DM, or 2.5 tons of DM in 1,000 tons of corn silage. Why spend the money to grow, harvest and ensile the crop if you're going to let your profits leak away?
In spite of recent progress, many farmers still aren't using silage processors correctly. This is confirmed by the results of over 2,600 samples of processed corn silage submitted in 2013 to Cumberland Valley Analytical Services for a processing evaluation called the kernel processing score (KPS). Only about one-third of the samples were graded as optimum, while 13 percent were graded as poor. In many if not most cases, the problem was probably due to improper processor roll clearance.
The common recommendation is a roll clearance of 1 to 3 millimeters, but from the KPS we're seeing, it's obvious that one of three things has been happening: First, the farmer or custom operator is setting the roll clearance at 3 millimeters but not decreasing the clearance as crop conditions indicate a need for it, including increasing grain maturity and differences in corn hybrid kernel texture.
Second, the roll clearance is set at 3 millimeters at the start, but is soon increased to something more than 3 millimeters in an effort to increase the rate of harvest. Custom operators occasionally do this, though most are highly reputable. This may be one more reason to price custom harvest by the hour instead of by the acre or ton.
I mentioned the following in an article last summer, but it's worth repeating: In one research trial, when corn was processed at a 2-millimeter roll clearance, milk production was 84 pounds per cow, but when the corn was processed at 4 millimeters, each cow only produced 75 pounds of milk. DM intake was the same with both processor settings. That's a difference of about $2 per cow per day, all due to a simple adjustment. The most likely reason for the milk production difference: Starch digestibility was 87 percent in the silage that was processed at 2 millimeters, versus 75 percent digestibility at a 4-millimeter roll clearance.
A third reason for a low KPS is worn processor rolls. John Deere sells a measuring tape for its processor that can be wrapped around the roll to indicate when it's worn enough to need replacing. A custom operator in Ontario uses a simple and inexpensive technique for his processor rolls: He runs his finger along the processor roll, and if the edge is sharp enough to cut his finger, he concludes that it's not yet time to replace it. (I said that it was simple and inexpensive, not that it was painless.) Regardless of how you check for roll wear - and we're not recommending that you slice up your fingers in the process - check each roll in several places, since wear may not be uniform.
Checking processor effectiveness
A limitation of the KPS is that while it tells you what happened, the information comes too late to do anything about it. That's why it's important to check processor effectiveness several times during harvest, while there's still time to make adjustments. The easiest way is to take a representative 1-quart sample of chopped corn and pour it onto a sheet of newspaper or other flat surface. If you can find more than one whole kernel, the processor isn't doing its job, and you need to do some troubleshooting to determine the reason. This method of evaluation has been refined a bit, with a goal of no more than one whole or two half kernels.
Case IH offers four DC2 models and two DC3 models of rotary disc mower-conditioners, built to handle a variety of crops.
Photo courtesy of Case IH.
Shredlage is a relatively new form of silage processing that involves shredding the corn plant lengthwise instead of just chopping it crosswise. Particle length is longer than with processed corn silage, but research has found that the kernels are well broken up, resulting in a KPS that is significantly higher than that of corn silage that was silage-processed at a 3-millimeter roll spacing.
Research by Dr. Randy Shaver at the University of Wisconsin compared Shredlage to silage-processed corn silage and found that cows eating Shredlage produced an average of 2.2 pounds more fat-corrected milk per day. Much of the difference was almost certainly due to the higher KPS, since there wasn't any difference in fiber digestibility and only a small increase (just over 1 pound) in DM intake.
The first Shredlage unit was sold in 2011, so this technology is still very new, and we're all still learning about what to expect from Shredlage. The recommendation is that one of the two shredder rolls will need to be replaced soon after about 40,000 tons of corn have been harvested. That may sound like a lot, but at a corn silage yield of 20 tons per acre that's 2,000 acres, which is less than some custom operators chop in a single season.
What will be the impact of not replacing a shredder roll when it's worn? It's too soon to know for sure, but we strongly suspect that some of the low KPS in processed corn silage was because the owners tried to stretch just one more year out of the rolls. I saw the results of this on a large, well-managed dairy farm in northern New York. Even though the farmer tried to counteract the impact of the worn rolls by reducing the roll clearance to 1 millimeter, there were a lot of whole kernels in the silage. He admitted that they knew the rolls were worn but tried to squeeze another year out of the old ones.
Once processor rolls are worn they need to be discarded; there's no reconditioning or sharpening process that will renew them. There's still a lot about Shredlage that we don't know, but there will be enough units operating in the eastern U.S. this fall that a year from now we should be a lot smarter - or at least better informed. Stay tuned.
The availability of moderately large disc mowers that are not equipped with hay crop conditioners has improved, so now farmers are asking a logical question: Do I need to condition hay crops, or can I mow them without conditioning? The answer: It depends.
New York researchers found that as long as the crop is placed in a wide swath and is harvested for silage, including wrapped bale silage, it's not necessary to condition it using either double rolls or impellers (tines). The "no conditioning" practice may work better with forage chopped a few points on either side of 35 percent DM versus drier hay crop silages, but opinions differ on this point. We don't have data on using this system for dry hay, and unless/until there is some reliable data showing that it works, we wouldn't recommend it. Better safe than sorry.
Mergers and tedders
These implements are used to move windrowed forage after the crop is mowed. A merger permits the combining of two or three mowed swaths into a single windrow. Combining windrows results in much faster chopping, since most forage harvesting operations (either self-propelled units or tractors operating pull-type choppers) have more than enough horsepower to do the job. It can also result in a more uniform chop length (fewer long pieces), especially in second and third cuts where yields may be low.
I much prefer a merger to a hay rake, since rakes can pick up surface debris and thereby increase the ash content of the resulting silage. There's less disturbance of the windrow and therefore less leaf loss in legumes. There's also less chance of scraping the soil surface, which can contaminate the forage with soil. It's estimated that hay crop silage made using a merger versus a hay rake will result in 1 to 2 percent less ash.
If you purchase a windrower, make sure you get one properly sized for your mowing equipment. A merger is one piece of equipment you should try in the field before you buy it to make sure it will do the intended job.
Tedders are commonly used in the making of dry hay, but as more farmers have started to harvest winter cereals for spring forage, they're being used to get this high-moisture crop dry enough to chop and ensile. Even managed in a full-width swath, a good crop of winter triticale is tough to dry, so tedding is often necessary. However, take care to operate the tedder at a slow speed; if you go tearing into one of these heavy swaths you could quickly turn your tedder into an expensive pile of scrap metal. You want to expose more of the forage to the drying effects of the sun, not fling it all over the field.
When shopping for a tedder, make sure the equipment dealer knows your intended use so they can recommend one that will be heavy-duty enough to do the job.
Ev Thomas has worked as an agronomist in New York for 48 years, first with Cornell University Cooperative Extension, then with the William H. Miner Agricultural Research Institute in Chazy, New York, 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.