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Steps for Evaluating a Pasture
Based Ration
Review hay
and grain based ration first (Evaluating
Hay Grain Diets).
Rations can
be evaluated on either an as sampled or dry matter
basis. The hay & grain ration evaluated on this site was developed
using as sampled results. This was possible because hay
and grain are similar in dry matter content, which in the absence
of analytical values is assumed to be about 90%. Since pasture
is wetter and lower in dry matter (20-25%), it is simpler to balance
the ration on a dry matter basis.
There is also
the challenge of estimating daily pasture consumption. Most livestock
species eat to satisfy a need for total pounds of dry matter.
Knowing the predicted total intake, will enable you to estimate
total pasture intake.
This ration
will be balanced on a dry matter basis. (Go to as
sampled vs. dry matter basis for more information.
The horse
in this example is an 1100 thoroughbred mare, lactating, with
a two month old foal. Although all components should be evaluated,
for simplicity's sake, we'll just focus on crude protein (CP).
| 1. |
Refer
to the Nutrient
Requirement Tables (NRC)
to determine the daily protein requirements. Requirements
are based on body weight, activity level, growth stage and
reproductive status. |
|
|
Protein
required for 1100 lb. horse, lactating with a two month old
foal = 1427 grams /day. |
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| 2. |
Feed
consumption |
| |
| a.
|
Weigh
amounts of hay and grain fed. |
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Hay
= 8 lbs. |
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Grain
= 12 lbs. |
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|
 |
| |
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| b. |
Calculate
lbs. of dry matter supplied from the hay and grain. |
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|
| |
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As
fed, lbs.
|
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%
Dry Matter |
|
Dry
matter, lbs. |
Hay
Grain
|
8
12
|
x
x
|
90/100
90/100 |
=
= |
7.2
10.8 |
| Total |
|
|
|
|
18.0 |
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|
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| |
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| c. |
Go
to the Dry Matter
Intake Table and find estimate of total daily dry
matter intake. For this horse, estimated daily intake
is 2.3% of body weight. |
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|
| |
| |
Calculate
total daily lbs. of dry matter consumed: |
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|
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1100
x (2.3/100) = 25.3 lbs. of dry matter. |
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| d. |
Estimate
pasture consumption as follows: |
|
| |
| |
Total
intake
|
25.3
lbs.
|
| Hay |
-
7.2 lbs. |
| Grain
|
-
10.8 lbs. |
| Difference |
7.3
lbs. |
|
|
|
| |
Pasture
consumption will be approximately 7.3 lbs. of dry matter to
satisfy the total daily need for dry matter. If the pasture
is 25% dry matter, the as fed amount (or adding the
water back in), equals 29.2 lbs. (7.3/(25/100)). We'll continue
to use the dry matter figures to evaluate this ration.
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| 3. |
Calculate
grams of CP supplied: |
| |
| All
values as fed |
|
Lbs.
of DM |
CP,% |
CP,
grams/lb. |
CP,
grams fed |
| Hay |
7.2
|
6.7 |
30.4 |
219 |
| Grain
|
10.8
|
13.3 |
60.3 |
651 |
| Pasture |
7.3 |
19.0 |
86.2 |
629 |
| Total |
|
|
|
1499 |
|
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| 4. |
Calculate
deficiency or excess: |
| |
Daily
CP supplied
|
1499
|
| Daily
CP required |
1420 |
| Difference |
+79 |
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|
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This
ration supplies excess protein. Pasture, especially lush,
early season pasture, is often high in protein. This usually
results in the total ration being high in protein. In this
example, lactational demands place a premium on protein
in the diet and the overage will insure that her daily protein
needs are met.
Work
with your nutrition professional or veterinarian to monitor
body condition and other factors. Make adjustments as advised.
This
is a simple illustration of using analytical values to evaluate
your ration. Other factors such as body condition, health
history and environmental factors should be taken into account
to best design a sound ration for your horse. Consult with
your nutrition professional or veterinarian to help you
formulate a ration designed to insure the health and longevity
of your horse.
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