Have You Ever Wondered Why

Robb D. Wock, Dairy Production Consultant, Purina Animal Nutrition(507)696-6351

Have you ever wondered why: …

  • Feeding almost an identical diet on 2 different dairies doesn’t produce the same milk?
  • Feeding a diet currently making 75# produced 85# the previous year?
  • Cows producing 3.2% milk fat appear healthy, with good reproduction?
  • Milk production jumps up 5# when diet formulation didn’t change on paper?

These scenarios commonly play out on every dairy at one time or another, and often differ from one year to the next.  While we all realize there are many factors known to influence these scenarios it is most likely they are the consequence of variation in certain nutrient profiles that were neither understood, measured, or controlled.  In other words, we missed something that made a significant impact on the cow.

In the nutrition world today “starch” digestion and our understanding of energy partitioning oftentimes is the key to unlocking your success.  And so it is that “starch” receives so much attention, and is a subject with significant opportunity.  However in order to really understand

What happens to starch in the cow it is imperative we review the development & physiology of a corn kernel (Table 1).  The remainder of this article will concentrate on “what corn is telling us from the inside”, and give you some food-for-thought as to how you can better manage it.

Table 1:  Inside a kernel of Corn

A kernel contains 2 types of endosperm, Floury (A) and Vitreous (B).  This endosperm is what

The cow uses for “starch”.  At full maturity dent corn contains ~ equal proportions of floury to vitreous starch, whereas Flint genetics contain a much larger proportion of Vitreous.  Floury endosperm is much more open in structure, so it is softer and more easily invaded by bacteria & microorganisms.  It is opaque in appearance.  Vitreous endosperm on the other hand, is much tighter in structure, so it is harder and more difficult for microorganisms & bacteria to invade. Vitreous appears more translucent.

 The Vitreous endosperm can range from 25-80% in dent corn, with almost none present in other grains such as Barley, Oats, & Wheat.  However by in large the starch make-up of dent corn commercial hybrids ranges from 55-65%.  Maximum levels of Vitreous starch are achieved typically once kernel moisture levels fall below 30% and the crop reaches physiological maturity.  Vitreousness also increases with increased “test-weight” and whenever Nitrogen fertility is at its highest.

 Germ (C) contains the embryonic tissue.  Most ash, oil, and essential amino-acids are contained in the germ.  Germ is a larger portion of the kernel in “Hi-Oil” varieties at the expense of starch.

As a matter of fact, for each 1% increase in oil you can expect a 1.3-1.5% decrease in starch!

 Pericarp (used for bran; outside “skin” of the corn kernel) makes up about 3-5% of corn.  It can remain attached to some starch depending on maturity, growing conditions, and variety.  Depending on the severity of attachment this can also limit the ability of microorganisms & bacteria to access the starch.  Sometimes larger kernels are advantageous because the pericarp takes up less surface area as a % of total starch weight.

 With this understanding of the physiological make-up of the corn kernel you should be better equipped to manage the starch and its impact on energy metabolism.  Here are some tips:

  • FLINT varieties are not your 1st choice for “feed”.  However if you do feed them make sure you are aggressive in processing.
  • Remember that while a higher proportion of “floury” corn makes it easier for Rumen microorganisms to degrade the starch, it also makes it easier for bacterial-invaders (i.e. molds) to damage & ruin your crop if harvest and/or storage conditions are Inadequate!  Never compromise harvest management for variety selection!!
  • Ensile Hi-Moisture Corn above 30%, and Earlage/Snaplage above 40% to improve starch digestability & energy availability.
  • If ensiled corn falls well below moisture targets expect to process more aggressively. 
  • Higher “test-weight” may also need additional processing.
  • Whenever possible plant “feed” varieties that favor higher ruminal starch degradability.
  • If you become involved in “Hi-Oil” varieties remember to account for the differences in starch vs. oil.  This is particularly important as you evaluate the dietary oil content from other sources of “oil” on the Dairy, and its implications on Ruminal-Unsaturated-Fatty-Acid-Load (RUFAL) or Poly-Unsaturated Fats (PUFA).
  • Finally, talk to the Lactation Dairy Nutrition staff at All-American Co-op about measurements to estimate rumen-degradable starch.  Use of advanced technologies in this area such as CALIBRATE set us apart and allow us to make better informed nutrition recommendations that will help improve forage utilization & profitability on your Dairy.  After all, we are only as successful as we help YOU become!  It is our sincere hope that you are blessed with abundant health & prosperity in 2017!
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