Minerals "In the past five years, there has been abundant literature
on bone mineral content, availability of organic versus inorganic sources,
emerging significance of previously considered minor minerals, and effects of
growth, exercise, or sedentary status on mineral metabolism," Rich
said.
She mentioned the use of a biopsy of the 12th rib as a diagnostic
tool in evaluating mineral status, especially calcium. In addition,
computed tomography can also estimate bone mineral content and differences in
bone density.
Chromium--This mineral is not well understood, but a new
study has shown that chromium tripicolinate supplementation can increase the
rate at which glucose is metabolized. However, further research failed to
show an effect on growth rate and development in yearlings, and there was
little effect on metabolic, hormonal, and immune response in mares feed a
Bermuda grass hay diet. In addition, supplementation of growing, sedentary,
and geriatric horses with chromium tripicolinate or chromium-L methionine had
no consistent effect on growth, immunity, or glucose/insulin
responses.
Molybdenum--Despite reports in other species of a detrimental
effect on copper absorption and retention with molybdenum supplementation,
horses seem to be immune to this.
Aluminum--Short-term addition of
aluminum to the diet did not affect the digestibility and mineral metabolism
of calcium, phosphorus, magnesium, zinc, copper, and
boron.
Silicon--In a study involving young Quarter Horses in race
training, zeolite A, a silicon-containing supplement, was fed. Researchers
found less bone-related injuries in the supplemented group. In addition,
supplemented yearlings had increased plasma silicon concentrations and
decreased bone resorption. However, the study did not determine if bone
strength was improved. Rich said that there seems to be promise in
supplementing injured young horses with silicon.
Iron--Liver biopsies
of horses fed excessive amounts of iron as ferrous sulfate showed no
abnormalities. Therefore, it was concluded that horses or ponies are unlikely
to develop iron toxicosis by over-consumption from this source of
iron.
Manganese--One study confirmed that horses require the level of
manganese recommended by the National Research Council (NRC). This level is
40 ppm, and Rich said that horses in regions known to be deficient should
be supplemented. In the study, horses receiving 40 ppm gained more weight,
had better feed efficiencies, higher serum copper, higher serum
hydroxyproline (an indicator of bone resorption), and a higher total bone
mineral content than those fed a diet deficient in manganese.
Copper,
Zinc, and Manganese--A study comparing exercising horses to sedentary horses
supplemented with copper, zinc, and manganese found that exercising horses
have an increased need for zinc. Exercise had no effect on the digestibility
or maintenance requirements of copper and manganese. Rich said that NRC
values for zinc in working horses might be underestimated.
According to
Rich, replacing half of the inorganic form of copper, zinc, and manganese
with an organic form (also known as chelated or proteinated) in the diet did
not affect liver concentrations of these minerals, did not improve immune
response, and did not improve hoof wall growth rates, hardness, tensile
strength, or trace mineral content in the hoof. Replacement in broodmare
diets was not beneficial. In general, it was found that inorganic forms of
these minerals were just as effective as organic forms.
Another study
found that organic copper and zinc might increase copper and zinc retention
and have slight benefits for copper digestion.
Selenium--Inorganic and
organic forms of selenium were compared in exercising horses. The inorganic
form of selenium-enriched yeast was more digestible with greater retention
than sodium selenite.
Calcium, Phosphorus, and Magnesium Involved in Bone
Density--Horses which have been confined to a stall or deconditioned for at
least 12 weeks with minimal exercise experienced a decrease in bone mineral
content. Supplemention at twice the currently recommended calcium level made
no difference. "After 12 weeks of stall confinement, loss of mineral
content might have weakened bones," said Rich. "Great care should be used in
the reconditioning process to avoid skeletal injuries."
Further
research found that higher levels of calcium and phosphorus in the diet
allowed greater bone turnover in all ages, but young animals have the highest
turnover. According to Rich, inactivity results in lower bone density, and
when exercise begins, there is an increased risk of injury in older
horses.
Protein In one study, fillies were either fed a diet of 40%
alfalfa hay or soybean meal supplemented diets. Growth measurements were the
same for both diets, but the group fed the soybean meal retained more
nitrogen, suggesting more protein muscle gain. However, in a study where 60%
alfalfa hay cubes were the supplemental source of protein, growth rates were
satisfactory in stock-horse type weanling fillies. Breuer pointed out that it
is important to provide supplemental phosphorus and trace minerals in diets
with large amounts of alfalfa.
A study was done to determine the
pre-cecal digestibility of protein and lysine in alfalfa cubes and in mixed
concentrates with graded levels of protein and lysine. It was found that
pre-cecal digestibility of protein and lysine in high-quality alfalfa was
only 60% of that of the concentrate mixes.
According to Breuer, most
mature horses are fed more protein than is needed. Therefore, protein levels
for mature performance horses can be reduced if adequate levels of amino
acids are maintained. Researchers fed horses two different diets--one with
14.5% crude protein and one with 7.5% crude protein with supplemental amino
acids. There was no deficiency observed with the lower protein diet. "Horses
require amino acids, not proteins," he said.
Vitamins A study done at
Rutgers showed that supplementing weanlings with 10 grams per day of vitamin
C and 800 international units (IU) per day of vitamin E after a long trip
improved vaccine response, reduced upper respiratory infections, and reduced
days that they were off feed compared to non-supplemented weanlings. Another
study found serum ascorbate and tocopherol concentrations were higher in
horses that had been supplemented with vitamins C and E. Rich recommended
that performance horses receive supplementation.
Another study found
that oral and natural form d-alpha-tocopherol was the most effective form of
vitamin E. continued next
thread
--- Outgoing mail is certified Virus
Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.510 /
Virus Database: 307 - Release Date:
8/14/2003
