Feed shrink, the dairy manager’s nemesis



FARGO, N.D. — Even before ethanol production, corn was the king of dairy feeds, especially as the forage of corn silage.

Advances in corn hybrid genetics have presented many improvements in the production of food and fiber for our world.


Feed shrink, the dairy manager’s nemesisFeed shrink, the dairy manager’s nemesisThe role of corn silage never has been as prevalent as it is today in the diets of lactating dairy cattle for the production of one of nature’s most perfect foods, milk.

Unfortunately, the costs to provide the feed to dairy cows in return for this precious food have become astronomical. Feed represents the most costly cash outflow for dairy cattle producers, and the cost to raise or buy that input has reached record levels.

Worse yet, this has happened at a time when the cash inflow from selling milk is at a record low price and comparable to the price received 30 years ago.

So while dairy farmers start out each day just trying to keep their business afloat, astute managers are fine-tuning every aspect of their operation to that end.

Feed bill

One obvious area is the feed bill. One major component to the feed bill is corn. And because dairy cows need forage, and corn silage is an excellent forage that is high in energy, corn silage is not likely to be eliminated from the ration any time soon.

As my revered predecessor, George Fisher (former North Dakota State University Extension dairy specialist), once said, “You can’t make a silk purse from a sow’s ear,” or in other words, to make milk, you need to feed the cow quality and quantity.

One very useful method to keep quantity and quality in the feed yard is to reduce spoilage losses. With wet feeds such as corn silage, the losses can be very high.

If, for example, a dairy producer harvests 25 acres for corn silage and the yield is 20 tons per acre, then 500 tons of corn silage should be available to be incorporated into a ration to be fed to the dairy herd during the next 12 months.

But will that amount of corn silage really be available for the year’s feeding? The answer, unfortunately, is no. Losses include dry-matter loss through fermentation, wastage and spoilage.

The bottom line is that such losses affect corn silage inventory.


The question producers ask, especially this year, is: How much wastage and spoilage is acceptable? Dry-matter loss with fermentation and feeding should be less than 10 percent, yet on some farms, losses can be as great as 25 percent or more.

When evaluating yield, getting 2 to 5 tons less corn silage yield per acre than anticipated is disappointing. Yet, losing 2 to 5 tons per acre in storage or through the farm’s feeding system practices is easy if everything possible isn’t done to prevent wastage and spoilage.

Therefore, the cost of producing the corn silage also has to take into account the feed losses that don’t get to the bunk. Decreasing feed shrinkage is a good management strategy to help reduce these costs.

Prevent spoilage

What management practices can help prevent spoilage? Let’s look a little more in-depth at silo packing management. For bunker silos, tractor weight, packing time, layer thickness, height of silage and moisture content all affect packing.

The goal is to achieve a silage density of greater than 16 pounds of dry matter per cubic foot. High silage density increases storage capacity and reduces silage porosity, which reduces oxidation loss and preserves the high feed quality harvested.


A University of Wisconsin formula for packing in a bunker silo is as follows: divide the pack tractor weight by 800 to get tons of silage that can be packed per hour. A 40,000-pound tractor can pack about 50 tons per hour. This equates to about seven wagon loads (7 to 8 tons per wagon) in a one-hour period for adequate packing to be achieved.

The most desirable method of packing bunker silos is the progressive wedge method, in which silage is packed continually on a 30 percent to 40 percent grade.

This minimizes the surface area that is open to exposure to the air that can result in dry-matter and forage-quality losses. If this is not possible, then silos should be packed by spreading relatively thin layers of silage (6 inches deep) and packing it well.

For silo bags, research from the U.S. Department of Agriculture’s Forage Research Center in 2002 indicates the effects of dry-matter content on density in corn silage varied by bagging machine.

Core samples taken at the face of bags during emptying found considerable variation in density. The outer inches on the top and upper sides had densities on average of 40 percent of those in the center and lower portions.

This suggests the need for higher feed-out rates than might be anticipated for similar average densities in bunker silos. Knowing that dry-matter densities in bag silos can vary by machine and operator also is important.

If hiring a custom bagger, the dairy producer must have the assurance the operator is filling the bags properly and obtaining the correct density.

Monitor routinely

Also, substantial spoilage losses can occur if bags are not monitored routinely for holes and patched or if overly dry silage (greater than 40 percent dry matter) is fed out in warm weather.

The quality of this year’s corn silage has yet to be determined. Although tempting when trying to salvage every bit of feed harvested, do not try to stretch the corn silage inventory by feeding spoiled silage to the dairy herd.

The quality of the total mixed ration (TMR) mix should not be compromised by incorporating spoiled silage into it. Poor-quality corn silage in the TMR creates a poor-quality TMR ration.

Feeding spoiled silage, even at only 5 percent of the total ration dry matter, will reduce intake. Nutrient digestibility and rumen health is compromised.

Harm forage mat

The spoiled silage can harm or destroy the forage mat in the rumen. Cows then will be more susceptible to metabolic disorders, displaced abomasums and hoof problems.

This also means the producer loses milk production, and/or they have the added cost of replacing lost energy and protein in the ration to compensate for the poorer quality.

And remember, feeding spoiled silage to dry cows and young heifers can have a negative impact on their fertility and reproductive efficiency as well.

So, if you have too much spoiled silage in your storage system and too much shrinkage of corn silage inventory on your farm, then now is the time to determine some management strategies to change that situation before corn silage harvesting begins.

(J.W. Schroeder is a dairy specialist with the North Dakota State University Extension Service.)

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