Hitting the numbers this corn silage season (Jon Urness)

Posted on August 4, 2014 in Forage Foundations
By Jon Urness, national forage specialist
Getting it right when it comes to corn silage harvest and storage has become more and more critical as it’s often the dominant forage in today’s dairy rations.  And you get just one chance.  You don’t get any “do-overs” or “mulligans” when it comes to putting up a year’s supply or more of corn silage.

The critical areas for getting it right include processing and particle length, moisture, density, good covering, and fermentation. So what are the numbers we want to hit?

Shoot high on this one. Industry standards may say that a kernel processing score of 50 to 70 is adequate, but we recommend being at the high end of that range.  If you’re not achieving a score of at least 60, you are sacrificing starch digestibility. Dr. Kevin Shinners, University of Wisconsin-Madison biological systems engineering researcher, shares these recommendations:

For cows to digest the starch in corn efficiently, the kernels in chopped and processed whole-plant corn silage must be broken into small particles.  Three decades ago, it was thought that effective starch utilization occurred if the kernel was merely nicked or broken.  With today’s high-producing animals, we know kernels must be processed into smaller particles for dairy cattle to get adequate starch utilization given the short duration feed resides in the rumen.

Chop length
Chop length is largely dependent on moisture, but is also critical to adequate particle length in the TMR. Recommendations for adequate particle length suggest that 10 to 15 percent of a corn silage sample should remain on the top screen of a Penn State forage shaker box.  In order for that to occur, theoretical length of cut (TLC) needs to be approximately 16 to 20 mm.  That’s between five-eighths to just above three-quarters of an inch (see chart below).  Sometimes longer material is required to achieve adequate particle length.

TLC versus forage on top screen of Penn State forage shaker box
Based on moisture, here are some general guidelines for chop length:

<33% DM 3/4 – 7/8 in. 19 – 22 mm
33 – 38% DM 5/8 – 3/4 in. 15 – 19 mm
>38% DM 1/2 in. 12 – 13 mm
Shredlage® 7/8 – 1 1/8 in. 23 – 26 mm

Packing density
The goal should be a minimum of 15 pounds per cubic foot of dry matter or 45 pounds as-fed. With higher horsepower choppers and the need to harvest quickly, density is often dictated by the delivery rate of silage to the bunker or pile. The traditional way to calculate maximum delivery rate is to divide the weight of the packing tractor(s) by 800 to get maximum delivery rate per hour.

For example, if you have one 44,000-pound packing tractor and you divide that weight by 800, the maximum delivery rate into that unit is 55 tons per hour. With today’s larger choppers able to harvest five tons per minute or more, we often need more and heavier packing tractors.

Another way to calculate the required packing tractor weight is to do the math in reverse.  Estimate the delivery rate in tons per hour into the structure and multiply by 800 to get the needed tractor weight.  For example, if feed is coming into a bunker at 120 tons per hour, then you need 96,000 pounds of packing tractors (120 X 800).

New technologies in plastics have revolutionized covering strategies.  With the advent of true oxygen-barrier plastics like Silostop®, dry matter losses in the top layers of silage have been reduced considerably. Dry matter loses in the top three feet of silage under conventional plastic can be reduced from 27.3 to 8.4 percent with the addition of Silostop film, according to research done at Kansas State University.

The economics of such a strategy are solid.  For example, the top three feet of a 36-by-160-foot bunker contain 388 tons of feed (as-fed). With conventional plastic alone, the loss is 27.4 percent or 106 tons of feed according to the K-State research. But with the addition of a layer of Silostop 2-Step, the loss is reduced to 8.4 percent or about 33 tons of feed.

Let’s convert that extra loss into dollars.  The difference is 73 tons of silage as fed.  At $50 per ton as-fed, that’s a reduction in loss of $3,650. A roll of Silostop 2-Step for a bunker that size costs about $470.

Even if you hit all the numbers we’ve discussed so far, a good fermentation is still critical for successfully storing forage as silage. Without an inoculant, some type of fermentation is likely to occur, but it may not be a controlled fermentation that produces the correct acids. There’s a huge variation in the types of naturally occurring bacteria on a harvested crop, but there are often times more bad bugs than good bugs.  That’s why it’s critical to inoculate with a proven bacteria that helps direct the fermentation toward a lactic acid-dominated fermentation. Vita Plus has been successfully recommending Crop-N-Rich with MTD/1 for the past nine years to ensure a fast up-front fermentation dominated by lactic acid, quick pH drop, and reduced heating and dry matter loss.

In many cases, aerobic stability can be a challenge in feeds, even with a very good initial lactic acid-based fermentation.  Large feeding faces, slow feedout, high temperatures, and other factors can cause aerobic instability in even well fermented forages and high moisture grains.  These cases call for an inoculant that produces a slightly higher acetic acid level that essentially acts like a fungicide to reduce yeasts and molds.  For most forages, Crop-N-Rich Stage 2, which includes an up-front fermenter and a healthy dose of L. buchneri 40788 for enhanced aerobic stability, greatly reduces heating on feed faces and in the TMR.  For high moisture grains, L. buchneri 40788 applied at 600 cfu/g of feed is recommended.

Don’t sacrifice starch digestibility because of poor kernel processing. Corn is too expensive these days to have it go through your livestock undigested. Always consult with your nutritionist and consider your storage system when determining final moistures and particle lengths, but these guidelines are a good start. Good packing and covering practices will go a long ways toward achieving an efficient fermentation and feedout, but be sure to take advantage of the proven technologies of Crop-N-Rich MTD/1, Crop-N-Rich Stage 2 and Crop-N-Rich Buchneri.

Category: Forage Foundations
Forage harvesting
Forage inoculants