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Are you harvesting what you really want in your ration?

Bill Powel-Smith Published on 29 August 2014
Cows at the feed bunk

Today’s dairy rations increasingly rely on corn silage as the primary forage in diet formulations.

Farmers and nutritionists consider corn silage to be more consistent and economical to produce over other cereals, grasses and alfalfa crops.

Yet corn silage quality can vary greatly from year to year due to environmental influences. Changes in starch and digestible fiber levels from year to year can also impact both ration costs and herd performance.

In addition, management decisions about harvest timing and how to process and store corn silage greatly influence feed quality and cow performance.

The dairy industry is beginning to recognize that the growing environment is the biggest factor affecting yield and quality, and that those regions with varying soils and weather patterns are more prone to year-to-year silage variability.

Despite the fact that we have little control over weather, we can use sound agronomic fundamentals to help stack the silage feeding deck in our favor. Let’s explore a few ideas and practices that might help you gain more control over your corn silage consistency and quality.

Right product, right acre
Your farm’s dairy rations are based on the forages that grow best in your area and on your farm as determined by the soils, weather patterns and average heat-unit accumulation. These local factors influence specific hybrid performance and should be a major part of deciding which hybrids fit best on your farm.

We know from plant breeding that genetics can influence fiber digestibility by 3 to 4 percent (outside of those hybrids selected for higher digestibility like BMR); however, weather can affect fiber digestibility by as much as 12 to 13 percent.

The negative impact of weather on corn silage quality can be somewhat mitigated by carefully matching hybrid genetics with soil types, crop-management factors and disease potential of the growing environment.

The point is to look beyond yield and to focus on agronomic strengths (or weaknesses) of the hybrid to reduce agronomic risk.

With that in mind, demand local, multi-year data when assessing the yield and agronomics of any hybrid under consideration for your farm.

Preparing for the harvest window
One of the goals of properly selecting and placing hybrids is to end up with a sensible plan that optimizes both yield and starch content along with fiber digestibility at harvest.

Accomplishing this requires staggering planting dates and carefully selecting hybrid maturities so the majority of the crop can be harvested at approximately one-half to one-quarter milk line: approximately 63 to 68 percent whole-plant moisture. Doing so usually provides the optimum plant maturity for starch and fiber digestibility levels.

Hybrids can vary a few days on how fast sugars translocate from the stalk through the cob and into the kernels, and then how long it takes the kernels to reach black layer.

Local soils and conditions can play into the timing of these final weeks and days of maturation. We can use these insights about how long specific hybrids take to reach final desired starch and whole-plant moisture levels to help broaden our harvest window and maintain quality targets.

Processing silage
After preparing for a broad harvest window, the goal is to process and store the silage to take advantage of the feeding potential of the nutrients in that crop. Forage processing and length of cut are getting closer scrutiny in recent years as dairy producers increase corn silage while trying to minimize starch losses in manure.

We see some herds feeding forage levels at more than 70 percent, with the expectation of increasing that percentage. The concept of shredding or tearing the corn plant as it is chopped has allowed some farmers to experiment with chopping at a 1-inch to 1.5-inch length of cut rather than the conventional three-quarters of an inch.

Creating a higher differential between the processor’s rolls or using new, innovative processor designs appear to improve kernel damage, making it more available to the cows.

Careful monitoring of chop length and kernel processing throughout the harvest season is one valuable management strategy farmers can use to help determine silage consistency and quality.

Storing and preserving practices
Two critical management steps growers can influence are the delivery and packing of silage in the silo. The goal of silage fermentation is to drop the pH as fast as possible – to a stable range of 3.8 to 4.2. Packing helps force air out of the feed pile and accelerates anaerobic conditions.

The standard rule for calculating tractor weight for good packing is to multiply the tons of feed coming in per hour by 800. A visual rule of thumb is to level and pack in 3-inch to 6-inch layers at the rate feed is being delivered. If feed is coming to the pile faster than it can be leveled and packed, it is necessary to add more tractors or silage densities suffer.

Shape your pile and fill your bunkers so that you can drive over every inch of the bunker without your tires sinking in more than 3 to 4 inches before the next covering of silage is added. If the pile’s side slope causes the tires to slip to gain traction, then the pile is too steep; compaction will be poor and feed loss greater.

Just because you create anaerobic conditions necessary for pH decline, it does not guarantee that the proper bacteria will be present on the crop to efficiently manage fermentation.

Corn silage is notorious for possessing high levels of yeast. While silage is in the anaerobic state (fermented and still in storage), yeast is typically not an issue. However, when exposed to oxygen, yeast multiply quickly and can initiate heating and TMR deterioration, reducing both quality and palatability.

The proper application of a research-proven Lactobacillus plantarum inoculant speeds up the fermentation process; this is a vital management step to reduce shrink and preserve your investment in seed genetics.

Covering the pile or bunker as soon as possible after packing with an oxygen-barrier film and plastic and tires or similar weight, is equally important to preserving forage quality. Remember, implementing sound management practices can nearly eliminate spoilage and TMR heating.

Feedout and fermentation
Yeast spores arriving with the forage at harvest are culprits causing silage (and high-moisture corn products) to heat when feed is exposed to oxygen during feedout.

Reputable silage inoculants with Lactobacillus buchneri bacterial strains reduce yeast counts and help maintain fresh cool feed, even during the heat of summer.

When removing silage each day, use a piece of equipment that allows you to maintain as clean a face as possible that minimizes cracks, loosened feed and overhangs.

Digging into the pile with a bucket loader creates small fissures that allow air to penetrate and begin activating yeast and other spoilage bacteria several days before using that silage as feed. Infrared cameras and long-probe compost thermometers easily confirm this heating effect.

Five tips for corn silage success
The decisions and time we put into selecting, growing, harvesting and storing our corn crops can make all the difference in how consistent our feed is from year to year.

Environmental conditions have the final say in corn silage quality, but we have the ability to anticipate and plan for some weather challenges that seem to appear each year.

1. Start with sound information about hybrids tested in your area and get to know and understand what works best on your soils.

2. Plan carefully to manage the harvest window, and work to chop and process the crop the way you and your nutritionist have agreed is best for your herd’s unique diet.

3. Be sure to have adequate packing capacity that is matched with the rate at which choppers deliver the silage.

4. A research-proven, crop-specific inoculant provides a good insurance policy against lost quality.

5. Careful, timely covering that includes an oxygen barrier helps preserve your harvest.

With more planning and preparation, you can improve silage consistency year after year, and your herd will thank you for it.  FG

Because the dairy industry increasingly relies on corn silage as a consistent and economical feed, silage management becomes ever more critical. Photo by Mikeal Dixon

Bill Powel-Smith
  • Bill Powel-Smith
  • Dairy Specialist
  • DuPont Pioneer