Week 6

Ration Formulation

Dry-Matter and As-Fed

Text Transcript

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• Grass Pasture Example
  • Suppose a cow is consuming 100 lbs pasture per day. Is this a lot?
  
  • So, how much DM is the cow consuming per day?
  • First, determine the % DM in the pasture. 20 g / 100 g x 100 = 20%
  • Second, convert AF lbs to DM lbs. 100 lbs AF x 0.20 (or 20% DM) = 20 lbs DM
• Note abbreviations: DM = dry matter and AF = as-fed

• Example of DM AF conversion

Pasture Sample - 20% DM

	DM	AF	Math
CP, %	20	4.0	=20*20/100
Fat, %	5	1.0	=5*20/100

 

• Observations when converting from DM AF and AF DM
  • The calculation will always include the nutrient or component (i.e. ADF) and % DM in the decimal form. You have one of two options: multiply by % DM or divide by % DM.
  • When converting from DM AF the concentration is always less. Another way of thinking about this is dilution. The only difference between DM and AF is water. So what happens when you add water to a feed? Everything gets diluted, therefore concentration decreases.
  • DM AF concentration
  • When converting from AF DM the concentration is always greater. Again, the only difference between AF and DM is water. Another way of thinking about this is concentrating something by taking the water out. So what happens when you dry a feed or take the water out? Nutrients get concentrated, therefore concentration increases.
  • AF DM concentration

 

• Suppose you have a pen of 100 cows and you're delivering 5 tons of feed to this pen daily. What is the average daily DM intake for each cow or how many pounds of DM is each cow consuming?

• 5 tons x 2,000 lbs/ton = 10,000 lbs AF
• 10,000 lbs AF x 55% DM/100 = 5,500 lbs DM
• 5,500 lbs DM/100 cows = 55 lbs DM/cow/d