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Forage Utilization by Horses(4)
Julia S. McCann,
Associate Professor Animal
Science Department, University of Georgia
Republished with premission of: Horse Industry Section of Alberta
Agriculture/This paper has an expert rating
Forage Digestibility
As horse owners, many of us know how much
we feed, either by volume or weight. Weight is a more accurate
assessment of feeds than volume; all horse owners are encouraged
to feed by weight, not volume. If horses are stalled,
owners also are quite aware of manure production. Nutrient disappearance
between the amount consumed and amount excreted is indicative
of the digestibility of a feedstuff. Forage utilization in the
horse is not thoroughly documented, but much of the available
data has been summarized in Table 1. Standards of evaluation
include the percent dry matter (includes all nutrients
of a feed, digestible and indigestible), crude protein
(based on nitrogen content of the feed which is largely available
to the horse in most horse feeds), digestible energy (the
best indicator of feed quality; energy is the main nutrient required
by the horse), and neutral detergent fiber (an indicator
of fiber digestibility; lower numbers are desired). Readers should
note different methods of feeding and collection, forage preparation,
forage maturity, and types of horses fed prevent direct comparisons
between most varieties, but the values do provide a perspective
of forage digestibility.
Only one study reported digestibility of
grazed forages. Orchardgrass and fescue pastures had two of the
highest dry matter and crude protein values in Table 1. While
methodologies may be responsible for some of the difference between
hays, the higher digestibility values are perhaps more reflective
of horses' selectivity for more digestible forages. The whole
plant is cut for hay and horses cannot be as selective of plant
structures when consuming hay.
Six grass hays listed in Table 1 indicate
that dry matter digestibility ranges from 41 to 58% with an average
of approximately 50%. Crude protein digestibility was most often
in the low 60% range while digestible energy tended to average
in the upper 40 percentile.
Of three forms of alfalfa fed, dry matter
digestibility was similar to grass hays, yet crude protein and
energy digestibility values were greater than values reported
for grass hays. Based upon the National Research Council's report
on forages, alfalfa averages 2.24 Mcal/kg while most grass hays
average 1.5 to 1.9 Mcal/kg. Considering the higher initial nutrient
content along with the elevated digestibility values for crude
protein and energy in alfalfa, horse owners should realize that
less actual weight of alfalfa hay (compared to grass hays) may
satisfy or exceed the horse's nutrient requirements. Alfalfa
is known as the "Queen of Forages" and it truly is
a valued forage in many equine establishments.
An interesting study of a Canadian product,
Alfamaize, showed promising feed digestibility values when compared
to a 65% concentrate, 35% bermudagrass hay diet to exercising
horses (Table 1).
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Table 1. Digestibility values for various forages fed to horses.
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Dry Crude Digestible Neutral Det. Research
Forage Matter Protein Energy Fiber Source
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---------------(%)-------------
GRAZED FORAGES
Orchardgrass 65 73 NR 66 11
Fescue 62 76 NR 64
GRASS HAYS
Bermudagrass 43, 54 52, 68 44 44, 57 2, 3
Brome 39, 52 43, 64 36, 49 NR 4, 5
Fescue 41,45,56 63 41, 53 44,53,57 6
Orchardgrass 50 60 46 NR
Prairie 50 33 48 NR 6
Timothy 49 36,54 46 42 4
ALFALFA
Hay 52, 60 67, 75 NR NR 7
Wafers 53 69 NR NR 7
Pellets 52 68 NR NR 7
MIXED FEEDS
Alfalfa:Corn Cube 68 80 62 51 8
65% Concentrate:
35% Bermudagrass Hay 68 82 64 48 8
NR = Not reported
* = organic matter value does not include less
digestible components of dry matter
1 Moffitt et al., Virginia, Equine Nut. Physiol. Symp. 1987.
2 Aiken et al., Texas, Equine Nut. Physiol. Symp. 1987.
3 McCann et al., Georgia, Equine Nut Physiol. Symp. 1995.
4 Vander Noot et al., New Jersey, J. Anim. Sci. 31:351, 1970.
5 Redmond et al., South Carolina, J. Eq. Vet. Sci. 11:215, 1991.
6 Harbors et al., Kansas, J. Anim. Sci 53:1671, 1981.
7 Haenlein et al., Delaware, J. Anim. Sci. 25:740, 1966.
8 Younglove et al., Texas, J. Eq. Vet. Sci. 14:599, 1994.
Dr. McCann, Associate Professor, Animal
and Dairy Science Department, University of Georgia, has done
extensive research on preference and utilization of forage by
horses including palatability and digestibility. She works closely
with horse owners to develop horse rations that optimize forage
utilization.
Republished with premission of: Horse Industry Section of Alberta
Agriculture
Copyright ©1999-2000
Her Majesty the Queen in the Right of Alberta. All rights reserved.
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