Archive for January 26, 2011

It’s More Than Corn: Digestibility and Energy

Part 2

This next section will try to help explain the components involved when formulating a ration.

What is the difference between a concentrate and roughage?

  A concentrate is any feed that is under 20% in crude fiber and over 60% total digestible nutrients (TDN), the opposite of roughage which is over 20% crude fiber and under 60% TDN. Concentrates and roughages are mixed together to create a balanced ration to meet an animal’s nutritional needs and also their energy needs, based on their use.





Indian Wheat

Concentrate (Wheat)


Meadow Hay

Roughage (Hay)










What is TDN?

TDN is a figure that indicates the relative energy value of feed to an animal and is expressed in pounds and in percent. There are four factors that affect TDN: % dry matter, digestibility of the Dry Matter, amount of mineral matter in the digestible dry matter and the amount of fat in digestible dry matter. Basically, if you take a feedstuff and subtract the water and all of the non-digestible components, what you are left with is the TDN.

Feeds are grouped based on their percentage of TDN for cattle on an as-fed-basis.

 Group A – These are pure fats, high fat feeds, and high in digestibility: soybean oil, dried whole milk, cotton seed, soybean seed, and dried bakery product to mention a few. Read more…

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