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Estimating Pasture Intake
Whether
on a seasonal or continual basis, pasture is often the primary
feed in many diets. Pasture consumption must be determined to
correctly assess its contribution of nutrients to the diet. Unlike
barn-fed feeds that can be weighed, pasture intake must be estimated.
The understanding of a few basic concepts (Dry
matter Intake, As
vs. DM) will enable you to simply calculate pasture intake.
The
first step is to determine total dry matter intake. Total intake
is based on body weight, level of activity, reproductive status
and growth stage. Intake values are located in Dry
Matter Intake Table. Combining this information with the known
consumption of other feeds, enables the calculation of pasture
intake by difference.
Examples
A.
Pasture as the sole feed.
An
1100 lb. horse is on a maintenance diet. It spends the majority
of it's time on pasture and is ridden occasionally on weekends.
It's summer, and no hay or grain is fed in the barn. Pasture is
the sole feed. It's lush and 20% dry matter (80% moisture). From
the Dry Matter Intake Table, intake is estimated at 1.6% of body
weight.
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1.
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Calculate
Lbs. of dry matter intake. |
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Lbs.
dry matter intake = body weight x (%Dry Matter Intake/100) |
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Lbs.
dry matter intake = 1100 x (1.6/100) = 17.6 Lbs. |
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2.
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Calculate
Lbs. of pasture consumed, as fed. |
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Lbs.
consumed, as fed = Lbs. Dry Matter Intake /
(dry matter %/100) |
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Lbs.
consumed, as fed = 17.6 / (20/100) = 88 Lbs. |
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| Thus,
to meet it's daily need for dry matter, this horse will need
to consume 17.6 Lbs. of dry matter, which converts to 88 lbs.
of pasture as fed. |
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| B. Pasture
as one of several feeds. |
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| An
1100 lb. horse under light work is fed 7 lbs. of hay and 5
lbs. of grain in the barn and has open access to pasture.
From the Dry Matter Intake Table, expected intake is 1.8%
of body weight. The hay and the grain are both 90% dry matter
and the pasture is 20% dry matter. |
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1. |
Calculate
Lbs. of dry matter intake. |
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Lbs.
dry matter intake = body weight x (% Dry Matter Intake/100) |
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Lbs.
dry matter intake = 1100 x (1.8/100) = 19.8 Lbs. |
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2.
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Calculate
the Lbs. of dry matter consumed from hay and grain. |
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Lbs.
dry matter consumed = Lbs. as fed x (dry matter %/100) |
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| Feed |
Lbs.,
as fed |
x |
Dry
matter % |
= |
Lbs.
Dry Matter |
| Hay |
7 |
|
90/100 |
|
6.3 |
| Grain |
5 |
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90/100
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4.5 |
| Total |
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10.8 |
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3.
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Estimate
Lbs. of pasture dry matter consumed. |
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| Predicted
total dry matter intake |
19.8 |
| Calculated
amounts of other feeds |
-10.8 |
| Estimated
pasture dry matter intake |
9.0 |
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4. |
Estimate
Lbs. of pasture consumed, as fed. |
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Lbs.
of pasture, as fed = Lbs. of pasture dry matter / (dry
matter %/100) |
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Lbs.
of pasture, as fed = 9.0 / (20/100) = 45 Lbs. |
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| In
summary, pasture intakes are predicted estimates and will
vary depending upon the quality, quantity and availability
of pasture, as well as the individual horse. Monitor the body
condition of horses consuming pasture as the primary forage.
If they begin to lose weight, it's good evidence that they
are not consuming enough or that nutrient quality is deficient.
Consult with your nutrition professional and adjust the ration
to insure that daily nutrient needs are met. |
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