Dealing with 2019 Corn Silage Crop

Dealing with 2019 Corn Silage Crop
8/30/2019

Dealing with the 2019 Corn Silage Crop

The spring of 2019 was, in many areas, one of the wettest recorded. This was on top of saturated grounds from record rainfall in the months before. Due to wet planting conditions, and cold soil temperatures, we may be dealing with one or more of these situations on a given dairy:

  • Immature corn silage at harvest due to delayed planting and normal or earlier frost.
  • Lower total yield due to delayed planting
  • Lower yield due to fewer acres planted.
  • Fields with variability in plant maturities at harvest.
  • Corn that was planted late because of excessive moisture but later suffered from lack of moisture. Often drought-stunted plants may have normal or higher than normal starch levels because, even though yields take a big hit, the ear is a higher proportion of the total plant weight.  With lack of moisture at pollination however, we could have stunted plants with poor kernel fill.
  • Fields that got planted (maybe late, but not too late), had adequate moisture from rainfall and or irrigation. Because of higher than normal temperatures from mid-July, these areas may produce a relatively normal crop.

As a result, there will be lots of immature corn silage to deal with this harvest season.  Whether corn plants will make it to proper maturity (32-38% DM) will depend on actual planting date, variety maturity rating, accumulated growing degree units, and date of first killing frost (~280 F).  Under normal late summer weather, it takes 6-7 weeks to progress from silking to 32-35% whole plant dry matter.  So, if you have noted when fields have silked, add 6-7 weeks and compare that to average date of first frost for your area to determine the likelihood of any particular field making it to maturity. If silking happened after July it might take longer to reach maturity due to the cooler days some areas might have in September.

Harvest and Storage Considerations

Avoid putting immature corn silage in upright silos (especially concrete silos), as corn silage <30% DM will seep and deteriorate the lower staves.  Drive over piles and bunkers are better choices but the effluent will need to be managed. Follow normal silage management practices of filling, packing, and covering the top and sides with an oxygen barrier. During filling sample several loads to provide a base of information on nutrient values.  Note that soluble CP, ammonia, and possibly 7 h starch digestibility will be lower in fresh samples than those taken after several months in storage. Waiting for a frost to dry the corn silage is an option.  However, corn ears with tightly wrapped husks can mold quickly after a killing frost especially if, as often is the case, a period of warmer weather follows. Waiting for a killing frost also runs the risk of those fields, that may have been planted late due to wet conditions, to be soaked by rainfall again. Reports out of Ohio and other areas indicate that because of very wet soils early, followed by more recent extended dry periods, plants may not have developed solid root systems (specifically brace roots) and may be subject to lodging. If corn silage is harvested after a frost, or even after a stretch of cooler weather, a bacterial inoculant should be applied at harvest, as natural occurring fermentative bacteria numbers are reduced by low temperatures.  Immature corn silage will have lower starch fill of kernels. However, they will be softer and potentially the starch that is there will be more fermentable in the rumen.  We would still recommend normal kernel processing procedures, as there is likely to be variation within and between fields and it’s best to make sure all kernels are adequately processed. 

Feeding Considerations

Corn silage that is harvested immature, will have less starch, more fiber (NDF) and more sugar. The degree of grain development will determine these proportions. Normal corn silage runs between 30-40% starch. Immature corn (dough stage) can test 5-25% starch. Corn silage is a grass forage with an ear attached. The energy value of immature corn silage can be 80-95% of normal maturity corn silage – the proportions of the energy have shifted from starch towards fiber and sugar.  Within a particular hybrid, NDF digestibility (NDFd) can vary based on environmental conditions during the growing period. In general, in the early growth phase, prior to silking, higher soil moisture and higher temperatures tend to increase lignification and thus lower NDFd.  The plant grows a taller and thicker stalk. What were the conditions like during the pre-silking phase this year?  There was plenty of moisture early – from before planting – though the early growth phase was cooler, then the furnace was turned on and conditions turned dry in many areas from about mid-July.  It will be interesting to see how these conditions affected fiber digestibility in this year’s crop.  Since there are many factors that influence nutrient composition of immature corn silage, actual analysis will be more important than ever.  In some cases, it may be practical to isolate the most immature corn silage and target it for specific groups such as growing heifers and later lactation pens and far off dry cows. Ration formulation strategies can be fine-tuned once assays are completed. 

Since corn silage is both a forage (NDF) and a grain (starch) source, when one component goes up, the other goes down.  To correct formulation for specific targets for NDF (forage or effective NDF) and starch content -the substitution strategy is rather simple.  This example will show a comparison of normal vs immature corn silage.

Item

Normal Corn Silage

Immature Corn Silage

NDF, % DM

40

50

Starch, % DM

35

25

 

  • Forage NDF target = 20% of ration DM
  • DMI = 50 lb
  • Forage NDF  = 50 lb DMI x 20% forage NDF = 10 lb
    • Assume other forage supplies 3 lb of forage NDF (e.g. 7.5 lb DM from 40% NDF alfalfa hay or haylage); 7.0 lb of forage NDF needed from corn silage
    • Normal corn silage: 7.0 lb/40% NDF = 17.5 lb DM needed
    • Immature corn silage: 7.0 lb/50% = 14.0 lb DM

= 3.5 lb less DM from corn silage (but equal forage NDF)

  • Starch supplied by corn silage:
    • Normal: 17.5 lb DM x 35% starch = 6.1 lb starch
    • Immature: 14. 0 lb DM x 25% starch = 3.5 lb starch
    • 6.1 – 3.5 lb = 2.6 lb of starch needed to be supplemented
    • Corn grain is about 72% starch:
    • 2.6 lb/72% = 3.6 lb of corn needed.  Which is approximately equal to the difference in corn silage DM. 

In reality the math may not always work this clean, but there might be room in the diet to make up for the lower starch level in immature corn silage as we will be feeding less total DM from this corn silage to keep diet NDF level similar. 

The next level in formulation would be to consider fermentable starch. Experience has shown that we often don’t get the same performance (milk production) when substituting dry ground corn to make up for a lack of starch in corn silage. This is likely due to corn grain starch being less fermentable than corn silage starch.  This year it will be interesting to see if the starch in immature corn silage is more fermentable than normal corn silage, in which case supplement dry corn (with a bit lower starch fermentability) to make up the deficit in starch, may be beneficial. 

A confounding factor is, hay and haylage harvest was delayed due to the wet spring, leaving many dairies with non-corn silage forages that are lower in digestibility.  With lower forage inventory coupled with lower forage fiber digestibility, there could be more reliance on non-forage digestible fiber sources. Feeds such as whole cottonseed, beet pulp, citrus pulp, distiller’s grains, brewer’s grains, corn gluten feed, and soyhulls should be considered. 

In conclusion, it could be a challenging year for feeding cows, but when is it not? Variability within and between dairies and regions may be more pronounced this year than in most years.  With better knowledge of nutrition and more sophisticated models, we have the ability to deal with it and maintain cow performance.  It may just take more intense and frequent feed sampling and cow monitoring than in a ‘normal’ year. 

-Sources of information for this article were adapted from Drs. Larry Chase, Bill Mahanna, Rick Lunquist, and Mr. Ev Thomas.

CSA Animal Nutrition provided the content of this article.

For more information, feel free to contact your Nobis Agri Science representative

Tags: Corn Silage