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The latest research in equine nutrition from the 2005 Equine Science
Society meeting.
Hot Topics in Equine Nutrition
By
Edgar A. Ott, Ph.D.
The
19th Equine Research Symposium was held by the Equine Science
Society, formerly the Equine Nutrition and Physiology Society,
just outside of Tucson, Arizona, June 1-3, 2005. Two-hundred-seventy-six
scientists from all over the world presented papers on equine
nutrition, exercise physiology, production management and
reproductive physiology. Included here are several summaries
of equine nutrition topics from the Equine Science Society's
19th Symposium Proceedings.
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Omega-3
Fatty Acids
There is considerable interest in the effects of feeding omega-3
fatty acids to horses because of the positive effects of these
fatty acids in other species. Spearman et al., reported that
gestating mares, fed a mixture of corn oil and linseed oil
that provided an omega-6 to omega-3 ratio of about 2-to-1,
resulted in increased omega-3 fatty acids in the mare's plasma,
her milk and the foal's plasma. The results suggest that we
can alter the fatty acid status of the foal by feeding the
mare desired fatty acids. In a similar experiment, Kruglik
et al. fed either corn oil or a protected fatty acid (PFA)
mixture providing added omega-3 fatty acids to pregnant mares.
Mare plasma and milk omega-3 fatty acid concentrations were
increased in the mares fed the PFA as were those in the foals.
The mares that were supplemented with a protected fatty acid
mixture also produced colostrums that had higher IgG concentrations,
which could have positive effects on the immune system of
the foals. |
Providing Omega-3 fatty acids to broodmares
could strengthen foal's immune systems.
Photo by Summer Best |
Feeding omega-3 fatty acids to mature horses resulted in increased
red blood cell concentrations of the omega-3 fatty acidsEPA
(C20:5n3) and DHA (C22:6n3) but it took at least 23 days before
the increase was noted (King et al.). The Michigan State workers
compared a long chained fatty acid supplement (LC) providing
omega-3 fatty acids with corn oil to determine whether fatty
acids would influence joint inflammation in exercising horses.
The LC treated horses had higher plasma EPA and DHA concentrations
and a trend for the LC treated horses to have a longer trot
stride suggesting that the LC reduced the osteoarthritis problems
(Woodward et al.). "These studies suggest that horses
may benefit from using fat sources that provide higher levels
of omega-3 fatty acids than can be supplied by corn or soybean
oil. Fish oil is a rich source of omega-3 fatty acids but
it is not very palatable unless processed to remove the fish
odor. Linseed oil, or flax seed oil, are also rich sources
of omega-3 fatty acids and may be the source of choice in
horse feeding programs." |
Saccharomyces
Cerevisiae
Yeast and yeast by-products have been used in other species
for a variety of purposes. There is evidence in the literature
that the mannan oligosaccharide from the wall of Saccharomyces
cerevisiae may benefit the immune system. In another study,
Saccharomyces cerevisiae in pelleted form was fed to geldings
on an alfalfa-brome grass hay and 2 kg of corn. The yeast
supplemented geldings had higher cecal pH values than the
unsupplemented geldings at four-hours post-feeding. The results
suggest that yeast may alter cecal metabolism and reduce the
effect of starch overloads (Hall and Miller-Auwerda). |
Recent research suggests that yeast may
reduce the effects of starch overload. |
Protein
A number of authors have suggested that feeding high levels
of protein to growing horses has a detrimental effect on calcium
metabolism and subsequently bone mineralization. Texas A&M
workers fed 10 month old foals NRC (1989) or 130% of NRC (1989)
protein for 120 days. The results did not indicate a negative
effect of excess dietary protein on blood, fecal or urinary
pH. There was also no adverse effect of high protein intake
on bone mineralization. Additional analyses of the samples
and data is underway (Spooner et al.).
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Silicon
Supplementation
In earlier research, silicon supplementation of horses in
race training reduced skeletal-related injuries and increased
training distance to injury. A subsequent experiment using
calves as a model, silicon supplementation did not improve
bone strength, leaving the question of why horses benefit
from silicon supplementation unanswered (Turner et al.). The
source of silicon appears to be important. Weanlings fed sodium
zeolite A had higher plasma silicon concentrations than weanlings
fed azomite A, a natural source of silicon. All growth parameters
were similar on both diets (Mazzella et al.). The results
from the feeding of silicon to young horses have been mixed.
Again, the benefits may be dependent upon the diet of the
horse. |
A recent
study confirmed that high levels of protein in the diet had
no detrimental effect on growing horses. |
Perennial
ryegrass
Perennial ryegrass varieties vary in the amount of water soluble
carbohydrates (WSC) they produce. Two varieties, that were
not identified, were selected for normal (N) and high (H)
levels of WSC. The N variety had 224 g WSC including 166 g
fructan/kg dry matter. The H variety had 333 g WSC including
222g fructan/kg dry matter. The forages were ground and fermented
in vitro for 72 hours using inoculum from the right ventral
colon of ponies fed hay. Samples were collected at 0, 3, 6,
9, 12, 15, 25, and 72 hr. and analyzed for pH and lactate.
Levels of pH did not differ between forages at any time. Lactate
levels were higher for the H forage at 6 and 9 hr after inoculation
(Ince et al.). The results suggest that forages high in WSC
can increase lactate production in horses which may lead to
metabolic disorders including hind-gut acidosis, colic and
laminitis. When feeding perennial ryegrass or other spring
forages, dilute the pasture with grass hay, so that horses
do not consume excessive amounts of the pasture containing
high levels of fructans.
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Glycemic
Index
Of similar interest is the glycemic index of various feed
ingredients fed to horses. The glycemic index measures the
amount of blood glucose an animal derives from a meal of a
selected feed ingredient or ingredients. The blood glucose
level is indicative of how quickly the starch is processed
to glucose and how quickly it is absorbed.
The glycemic index is determined by feeding the ingredient
along with a standard diet of oats and alfalfa hay and measuring
the blood glucose levels before the meal and at 30, 60, 90,
120, 180, 240, and 300 minutes after the meal. The glycemic
index is measured as area under the curve when compared to
oats which is given a value of 100. Sweet feed, oats and corn
all had values that were high (95 - 110). Barley and wheat
bran were in the middle (55 - 76). Beet pulp, alfalfa, rice
bran and soybean hulls were all low (0 - 20) (Rodiek and Stull).
In another experiment, oats barley and corn were fed untreated,
finely ground, steam-flaked and popped. The glycemic index
did not seem to respond consistently to the processing even
though earlier studies have shown that processing improves
prececal starch digestibility in horses (Vervuert et al.).
The glycemic index is of value in trying to minimize the hind
gut starch overload that occurs when performance horses are
fed large amounts of feed concentrates.
The use of beet pulp, rice bran and
soybean hulls as ingredients in horse feeds appears to be
effective in reducing the glycemic index of the concentrate. |
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Dr.
Edgar A. Ott, Consulting Nutritionist for Seminole
feed, recently retired from the University of Florida,
Department of Animal Sciences.
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