What Protein Percent to Feed
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The question of what protein percent to feed is hard to answer because the sources of protein from the forage and the ingredients in the grain ration drastically affect protein utilization. The quality of protein and bypass protein characteristics of the components in the total ration can greatly alter protein utilization. In general, we can theoretically say that the protein percentage of the total ration (grain and forage) should be 16 to 17%.
Since most cows eat 20 to 22 lbs. of grain on average, one can say that grain comprises 60% of the total ration consumed by the cow. It then is very easy to algebraically calculate the protein desired in the grain ration.
Example One:
The producer is feeding orchard grass/alfalfa haylage free choice that is 14% protein on dry matter basis.
|
Forage
|
|
Grain
|
|
Desired
|
|
|
.4(14)
|
+
|
.6(x)
|
=
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15%
|
|
|
5.6
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+
|
.x.
|
=
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15
|
|
|
|
|
.6x
|
=
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15-5.6
|
|
|
|
|
.6x
|
=
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9.4
|
|
|
|
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x
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=
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% protein
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grain + 9.4/.6=15.66%
|
This producer should be feeding a 16% ration.
Example Two:
Producer is feeding 11 lbs. alfalfa (18% protein, 91% dry matter) and 53 lbs. corn silage (8% protein, 30% dry matter).
A) On a dry matter basis, the producer is feeding:
|
11
|
x
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.91
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=
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10 lbs.
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dry hay
|
|
53
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x
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.3
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=
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15.9 lbs.
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dry silage
|
|
|
|
|
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25.9 lbs
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dry matter
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B) Alfalfa comprises 10/25.9 or 38.6% of roughage and corn silage comprises 61.4% of roughage. Therefore:
|
Alfalfa
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38.6(.18)
|
|
6.95
|
|
|
Corn Silage
|
61.4(.08)
|
=
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4.91
|
|
|
|
|
|
11.86
|
protein from roughage
|
|
Forage
|
|
Grain
|
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Desired
|
|
|
.4(11.86)
|
+
|
.6(x)
|
=
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15%
|
|
|
5.6
|
+
|
.6x
|
=
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15
|
|
|
|
|
.6x
|
=
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15 - 4.74
|
|
|
|
|
.6x
|
=
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10.26
|
|
|
|
|
x
|
=
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% protein
|
graub + 10.26/.6 = 17.1%
|
This producer should be feeding a 17% ration.
For more information, contact Janice Spears at jspears@www.mfa-inc.com.
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