Does feeding dry corn silage ‘corn-cern’ you?

Posted on November 29, 2023 in Forage Foundations
By Paulina Letelier, Ph.D., Vita plus dairy nutritionist and technical services specialist

Many farms throughout the Midwest reported harvesting drier-than-ideal corn silage this season.  Recently, a producer in northeast Wisconsin told me they usually start chopping when the plant is at 32% dry matter (DM).  This year, they found fields that were already at 40% DM when they started.

Below are some strategies for feeding dry corn silages:
1.  Evaluate changes in nutritional composition:  Maturity of the plant alters the nutritional composition of the plant, mostly by increasing the proportion of kernel and reducing the proportion of stover.  These changes result in increased DM, starch and neutral detergent fiber (NDF) content.

Changes in starch:  Although the starch content of the plant may be higher compared to an immature plant, the starch digestibility could be considerably reduced when the DM of the corn silage increases more than 40% because the kernel gets harder.  Thus, it is more difficult to process kernels during harvest and rumen microbes cannot breakdown the kernels as easily.  This will increase post-ruminal starch fermentation and the risk of hemorrhagic bowel syndrome (HBS).  Make sure that the ration has adequate levels of fiber and ruminal starch to avoid overflow of starch to the small intestine.  Check fecal starch, which should be less than 3%.  Consider adding or increasing levels of monensin in the ration to maximize propionate production in the rumen.

Changes in NDF:  Making sure that the cows have sufficient ruminal effective fiber is crucial for rumen health.  Use a Penn State Particle Separator (shaker box) to estimate physically effective NDF (peNDF) by adding the percentage retained in the top sieves (above 8 mm) and multiplying the result by the percent of amylase NDF organic matter (aNDFom) in the total mixed ration (TMR).  When starch levels are 20% to 25% of TMR DM, it is important to include sufficient peNDF to prevent subclinical acidosis and maximize intake (Khorrami et al., 2021).  Research has shown that, when the corn silage DM is greater than 40%, lignin content significantly increases.  Consider adding non-forage digestible fiber sources to the ration, such as soyhulls or corn gluten feed, to increase the fiber digestibility.

2. Storage time:  During storage, bacterial activity is the main contributor to the breakdown of the prolamin protein matrix, which increases ruminal starch digestibility (Junges et al., 2017).  When feeding drier corn silage, leverage storage time to make energy more available for milk production.

3. Alternative feed ingredients:  When a high proportion of dry cow silage is included in the ration, it can affect the overall moisture of the TMR.  The TMR should have at least 50% moisture to keep cows from sorting long forage particles, which may reduce intake and milk fat.  If available, consider adding or increasing water or whey permeate in the diet.  Also, consider exchanging dry ingredients with wet ingredients such as wet distillers or brewers grains.  However, keep in mind that this replacement strategy could disrupt ruminal biohydrogenation and potentially cause milk fat depression.

4. Avoid mold and yeast if present:  Drier corn silages are more prone to spoilage for two main reasons:  (1) Dry corn silage is difficult to pack and (2) the feedout rate is typically lower because each pound of dry corn silage (e.g., 40% DM as-fed) contains more DM than a pound of wet corn silage (e.g., 35% DM as-fed).  This increases oxygen exposure into the deeper layers of the face.  High yeast counts in silages, resulting from oxygen exposure, can be detrimental to feed quality as they decrease net energy of lactation (NEL) content, increase shrink, disrupt rumen fermentation and depress digestibility.  Remove spoiled silage – especially in the top layer and shoulders of the silo – and evaluate your feedout rate to keep the silage face fresh.  Additionally, check silages routinely for mycotoxins as drier corn silages are more prone to mold and mycotoxins.  Work with your nutritionist to evaluate use of mycotoxin neutralizers, binders, and/or antioxidants like vitamin E in the diet.

5. Mix it right:  Drier corn silages require increased mixing time.  The corn silage should be added first in the mixer to maximize blending with other feed ingredients.

Category: Animal health
Feed quality and nutrition
Forage Foundations
Forage harvesting
Forage storage and management