A SUGGESTED VITAMIN AND MINERAL LEVELS IN HORSE RATIONS*
,'7"i t, " ".
T. J. Cunha, Chairman
Department of Animal Science
University of Florida G
It is unfortunate that less is known about the nutitionl- rquI ements of the
light horse than of any other farm animal. This is due to the small amount of re-
search which has been conducted with light horses. Most of the recommendations being
made today have been arrived at by extrapolating from the requirements of other farm
animals and from a limited amount of earlier information available on draft horses
and ponies. Thus, anyone asked to recommend nutrient levels for the horse finds that
he has a difficult and speculative job.
In this paper, the writer is recommending suggested levels of nutrients to be
used until more exacting information can be obtained by research studies. While
the writer would prefer not to make recommendations without research data, the horse
people need some guidance now and it will be many years before enough research in-
formation will be available to give them the exact help they need. It is felt that
the levels recommended herein will be better than many of those presently being used
by many horsemen. In many cases, the levels of nutrients being used are extremely
high, or out of balance, and actually may be causing harmful effects.
Vitamins for the horse
It is not known which vitamins need to be added to well balanced horse rations
and under which conditions. Most horsemen, especially those with horses used for
racing and performance show purposes, are adding vitamins to their rations. The
levels used vary a great deal and in many cases are extremely high. In an effort to
recommend reasonable levels to be used, for those who feel they should use them,
the writer has worked up recommended levels in this paper. It should be pointed out
*Address given at the Florida Nutrition Conference at Daytona Beach on October 24
and 25, 1968.
that these levels are guesses and are based mostly on experimental information ob-
tained with animals other than the horse. These levels can be used as a guide until
experimental information is obtained to more adequately determine the needs of the
horse. These levels should be better than some of those which many horsemen are now
using and can be used as a guide by them.
Table 1 gives a suggested vitamin mix for racing or performance show horses.
Table 1. Suggested vitamin mix for racing or performance show horses
Vitamin A, I.U.
Vitamin D, I.U.
Vitamin E, I.U.
Pantothenic acid, mg.
Vitamin B12, micrograms
Per ounce of pre-mix*
*Each ounce of the pre-mix would contain this level of vitamins.
Table 2 gives the recommended level of the vitamin pre-mix to be used with
horses during the various stages of their life cycle.
Table 2. Recommended level of vitamin pre-mix to be fed daily to horses
which are to be used for racing or performance show purposes
(a) from birth to 2 months of age
(b) from 2 months to weaning
(c) from weaning to training
(d) during training
(a) during gestation
(b) during lactation
(c) which are barren**
(a) not being bred during off season
(b) during breeding season
* These levels might vary some depending on stress factors
** This high level might be used for a period of 3 to 4 months in an
effort to get the mare to conceive.
Table 3 shows the level of the various vitamins consumed daily by horses if
the feeding levels recommended in Table 2 are followed.
Table 3. Levels of vitamins supplied daily per animal*
Foals Mares Stallions
2 mo. Wean- During
Birth to ing to train-
to 2 wean- train- ing Gesta- Lacta- Being
mo. ing ing tion tion Barren Idle bred
Vitamin A, I.U. 5,000 10,000 20,000 40,000 40,000 40,000 60,000 40,000 60,000
Vitamin D, I.U. 750 1,500 3,000 6,000 6,000 6,000 9,000 6,000 9,000
Vitamin E, I.U. 10 20 40 80 80 80 120 80 120
Thiamine, mg. 3 6 12 24 24 24 36 24 36
Riboflavin, mg. 5 10 20 40 40 40 60 40 60
Niacin, mg. 15 30 60 120 120 120 180 120 180
Pyridoxine, mg. 1.5 3 6 12 12 12 18 12 18
acid, mg. 6 12 24 48 48 48 72 48 72
Choline, mg. 75 150 300 600 600 600 900 600 900
Vitamin B12, mcg. 15 30 60 120 120 120 180 120 180
Folacin, mg. 1.5 3 6 12 12 12 18 12 18
wishing to add these vitamins in the feed can do so by estimating the average
of pounds of feed that the animals will consume daily during the various
of the life cycle and then dividing the figures shown in Table 3 by the num-
pounds. The result will be the amount which needs to be added per pound of
These vitamin levels are most likely higher than actually needed. Moreover,
some of the vitamins may not need to be added to a well balanced ration. The levels
recommended can be used as a guide until more exacting information becomes available.
For those who wish to supplement with only the minimum level of vitamins, since
they are not pushing their horses for racing or performance show purposes, the levels
of vitamins shown in Table 4 are recommended.
Table 4. Low level vitamin supplementation
Level of vitamins fed daily
Vit. A Vit. D Vit. E
Creep feed for foals 2,500 250 5
Ration for growing horses 10,000 1,000 20
Ration for mares -
gestation and lactation 20,000 2,000 40
Mature horses 10,000 1,000 20
Further information on vitamins used
Some additional comments are needed regarding some of the vitamins used in
Table 1. This will help clarify the possible need for using them at higher levels
The need for supplementing horse rations with vitamin E is not very clear. Many
feel that well balanced horse rations should have all the vitamin E needed. It is
possible, however, that there may be conditions of stress or strain or where the
vitamin E is destroyed or used up rapidly and thus extra supplementation might be
needed. There are many horsemen who feel that vitamin E supplementation will improve
fertility of mares and stallions.
Dr. M. E. Ensminger, while at Washington State University, recommended the
following daily doses of alpha tocopherol succinate in the feed: stallions and mares,
600 to 1,000 I.U. beginning a few weeks before breeding; and 2,000 I.U. for race
horses in training. There are reports from horsemen in Canada and elsewhere that
these levels are helpful.
Recently, Professor Howard Stowe of the University of Kentucky reported on a
study with mares that had been barren for 3 years. He reported that the feeding of
100,000 I.U. of vitamin A and 100 I.U. of vitamin E daily for 3 months resulted in an
improvement in conception rate of 64 per cent. Injecting the same level of vitamin
A and E increased conception rate 65.5 per cent. This is definite proof that these
two vitamins are very important in optimum reproduction with the horse.
Drs. F. G. Darlington and J. B. Chassels, Canadian veterinarians, have reported
that vitamin E supplementation decreased nervousness and greatly improved stamina in
racing horses. The feeding habits of their horses also became more regular. The
vitamin E treated animals were able to run farther and faster. They explained this
effect of vitamin E by stating that it improved the efficiency of oxygen utilization
by all tissues and cells of the body.
The pre-mix shown in Table 1 will result in a low level of about 20 to 30 mg. of
choline per pound of feed being supplied. The young pig requires about 500 mg. of
choline per pound of feed. Thus, the level added to the pre-mix is small and pro-
vides only insurance against a possible need in the ration.
At a recent conference in Indiana, the writer was told by a practicing veter-
inarian, who works extensively with horses, that the use of 6 to 8 grams of choline
(a 50 per cent choline product) daily was very effective against heaves in the horse.
While this fact has not been confirmed by research data, it is given for whatever
value it might have for those who might wish to try it.
Some vitamins were not included in Table 1. Since there may be cases when their
use might be considered by horsemen, some discussion on them follows.
Vitamin C (ascorbic acid)
The information available on vitamin C is conflicting and allows no definite
conclusions. There is evidence that when vitamin C is fed to horses that large
amounts are destroyed in the digestive tract. Studies with mares and stallions in-
dicate a correlation between breeding performance and blood vitamin C. However,
the feeding of vitamin C to barren mares has been tried only in a limited extent and
the results obtained are inconclusive. There have been some reports indicating that
on vitamin A deficient diets the vitamin C in the blood may become low. However,
this is not well established. This emphasizes, however, the importance of making
sure that horses obtain enough vitamin A in their rations. The only information
which might be used as a guide by anyone wishing to try vitamin C is that an adult
human needs about 75 mg. of vitamin C per day. The writer has talked to a number of
horsemen who felt that the daily use of 1,000 mg. of vitamin C helped hard-to-breed
mares to conceive. However, this is an observation only, and the work was not con-
trolled to make sure that the vitamin C treatment itself actually did the job. The
observation is being presented, however, for whatever value it might have since I
have heard it frequently. A lack of vitamin C in humans results in the symptoms of
scurvy, which include swollen, bleeding and ulcerating gums; loosening of teeth;
weak bones; and fragility of the capillaries with resulting hemorrhages throughout
There is no evidence that vitamin K needs to be added to horse rations. Some
horsemen, however, are adding it to their rations. There is no information available
on the vitamin K requirement of horses or beef cattle. The only swine information
available was obtained with the newborn pig, and it showed that the vitamin K re-
quirements were met with 2.27 micrograms of menadiol sodium diphosphate per pound
of bodyweight daily. The chick has a requirement of 0.24 mg. of vitamin K1 per
pound of feed. These levels might be used as a guide for anyone who feels that
vitamin K might be needed. A lack of vitamin K delays the clotting time of the
blood. A deficient animal may bleed to death from any injury or bruise that causes
rupture of the blood vessels. This means that one should determine blood clotting
time on any valuable animal before operating on them.
There is no evidence to indicate that biotin needs to be added to horse ra-
tions. There is no information available on the biotin requirement of horses or
beef cattle. A level of 90 micrograms per pound of feed prevented biotin deficiency
symptoms with the pig. However, this level is above the actual biotin requirement
which has not yet been determined with the pig. The biotin requirement for the
chick is 41 micrograms per pound of feed. These levels might be used as a guide
for anyone wishing to try biotin. A biotin deficiency in the pig causes a loss of
hair, spasticity of the hind legs, cracks in the feet and a dermatosis.
Inositol and PABA (Para-aminobenzoic acid)
There-is no evidence that the horse needs inositol. This vitamin has an
effect in preventing certain types of fatty livers. A lack of inositol also causes
growth retardation and loss of hair. Inositol has been used in swine rations at
levels of 0.1 to 0.3 per cent of the ration. This can be used as a guide for anyone
wishing to try inositol in horse rations.
PABA is part of the molecule of folic acid. Many believe that if the ration
is adequate in folic acid that PABA is then of no benefit when added to the diet.
The Kentucky Station published a report in 1966 showing that PABA increased the rate
of gain in foals fed a purified ration. Whether this same effect would occur with
a natural, practical type ration is not known. The Kentucky Station fed 100 mg. of
PABA per foal per day. This level can be used as a guide for anyone wishing to try
No harm in adding vitamins
There is no harm in adding the vitamin levels suggested in this paper. If
they are not needed, the extra cost of adding them is the only problem involved.
For the person who has racing or performance show horses, the matter of an addition-
al small cost for vitamins is of no consequence. Thus, they want to add them if
there is any possible beneficial effect to be derived from it. Since experimental
information is lacking on whether or not all the vitamins shown in Table 1 might
help, horsemen add them anyway as insurance against a possible need.
Table 4 recommends a low level of vitamin supplementation for those with
horses used for pleasure riding and other uses. These levels can be used as a guide
Minerals for the horse
There is very little research information available on the mineral needs of
the horse. This is very unfortunate since proper bone formation and sound feet
and legs are so important for the horse. The old saying "No foot, no horse" is
very true and this indicates the urgent need for mineral research since so many
bone ailments occur with horses.
Calcium and phosphorus
Table 5 shows the needs of the growing horse as worked out by NRC (National
Table 5. Calcium and phosphorus requirements of growing horses
For horses with mature weights of
Body 600 lbs. 800 lbs. 1000 Ibs. 1200 lbs. 1400 lbs.
Weight, lbs. Ca* P** Ca P Ca P Ca P Ca P
200 .40 .36 .46 .36 .52 .36 .56 .47 .66 .47
400 .41 .41 .40 .30 .33 .27 .35 .33 .40 .32
600 .18 .18 .28 .28 .27 .23 .30 .29 .29 .26
800 -- -- .21 .21 .23 .22 .30 .27 .26 .24
1000 -- -- -- -- .22 .22 .20 .20 .20 .20
1200 --- -- --- --- --- .21 .21 .20 .20
1400 -- -- -- -- -- --- --- --- .20 .20
Calcium in percentage of ration.
** Phosphorus in percentage of ration.
The data in Table 5 show that as the horse reaches a mature weight that its
needs for calcium and phosphorus decrease. This is because most bone deposition
has occurred by then. The data also show that horses with heavier mature weights
have a higher calcium and phosphorus requirement than smaller type horses when they
are young. However, all the horses have about the same calcium and phosphorus needs
when they approach maturity.
Table 6 shows the calcium and phosphorus needs of mature horses and mares dur-
ing pregnancy as recommended by NRC.
Table 6. Calcium and phosphorus needs of
mature horses and mares
For mares during
last quarter of
at peak of
* Calcium and phosphorus expressed as a percentage of the ration.
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The data in Table 6 show the importance of providing higher levels of calcium
and phosphorus during pregnancy and lactation.
It should be noted that the calcium to phosphorus ratio is about one part of
calcium to one part of phosphorus. During early growth this ratio approaches 1.5 to
1.0. In addition to a proper level and ratio of calcium to phosphorus, one also
needs adequate vitamin D for the proper absorption and utilization of these two
The writer feels that the horse being pushed for racing at an early age has
calcium and phosphorus requirements higher than those shown in Tables 5 and 6.
However, he would hesitate to recommend the levels to use until research information
is available. Calcium and phosphorus in excess can have harmful effects, and thus
the writer would not want to recommend different levels without experimental evi-
dence to use as a guide. One can recommend other nutrients, such as vitamins, trace-
minerals or protein levels slightly in excess without harmful effects. The only
effect is the added cost involved. However, the level of calcium and phosphorus to
use is so basic to developing a sound horse that one should not guess at it. Cal-
cium and phosphorus levels to use in horse rations would seem to be one of the top
priority nutritional problems to be solved by the scientist working on horse nutri-
Horsemen need to experiment on their own and gradually raise their levels of
calcium and phosphorus in line with the results they are obtaining with their horses.
If they are having leg problems, then they need to re-evaluate whether or not the
levels of calcium and phosphorus being used are adequate. Any increases in calcium
and phosphorus should be done gradually and enough time should be allowed to deter-
mine if the change in calcium and phosphorus is beneficial or not.
At a recent Conference on horse nutrition a few scientists guessed that the
horse should have a level of at least 0.6 per cent calcium and 0.45 per cent phos-
phorus in the total ration consumed. Whether or not this is a good guide only re-
search will tell.
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Salt added to the ration makes it more palatable and is very essential in many
body functions. Horses which are worked or exercised heavily require more salt
since they lose a considerable amount by sweating. Unless this salt is replaced,
the horse will soon show signs of fatigue or overheating.
It is recommended that salt be included in the concentrate mixture at a level
of 1.0 per cent. In addition, salt should always be available free-choice in a
mineral box wherever horses are kept.
Trace mineral elements
Horses need trace minerals. Unfortunately, there is very little experimental
information available on their requirements by the horse. Moreover, information
is lacking on how much should be added to well balanced horse rations. The data
shown in Table 7 can be used as a guide as to levels to add to rations of horses
used for racing and performance show purposes. These levels would be insurance
against a possible need in the ration. The cost of adding these minerals would be
small, and it is low cost insurance against a possible need with valuable horses
used for racing and performance show purposes.
For the person who does not have racing or performance show horses and who
does not wish to add the minerals shown in Table 7, it is recommended that they
use trace mineralized salt. Trace mineralized salt is available which supplies
minerals at levels which are close to those shown in Table 7.
Table 7. Suggested level of trace minerals to add to horse rations
Added per Added per Level added in needs which
pound of ton of ppm in the: are added
Mineral concentrate concentrate Concentrate Total to the total
element* feed** feed feed ration** ration***
Milligrams Grams ppm ppm %
Copper 2 4 4.4 2.2 25
Iron 10 20 22 11 25
Iodine 0.5 1 1.1 0.55 250
Manganese 10 20 22 11 50
Zinc 45 90 100 50 100
Cobalt 0.045 0.09 .1 0.05 100
All of these levels are based on the mineral element itself. Corrections will
need to be made depending on the source of mineral element being used. For
example, copper sulfate contains 28.5 per cent copper whereas copper oxide con-
tains 80 per cent copper. To supply 4 grams of copper one needs to add 5 grams
of copper oxide since it contains only 80 per cent copper.
** In general, concentrates make up about one-half the total feed intake of horses
throughout their life cycle. The remainder consists of hay and/or pasture.
Thus, the level of mineral element added to the concentrate ration should be
divided by two in order to obtain the level being added to the total ration.
*** Read discussion on each trace mineral to find how these levels were arrived at.
In arriving at the levels of trace minerals to add to the ration there is not
a good guide to use. The following reasoning was used in determining the levels
recommended in Table 7.
The pig's requirements are about 10 ppm of copper. Beef cattle needs are from
4.4 to 9 ppm of copper in the total ration. A level of 8 ppm may be adequate for
growing horses. Thus, all three classes of livestock have about the same require-
ment for copper. This fact was used as a guide in arriving at the level of other
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trace minerals to add to horse rations when data were lacking for either cattle or
the horse or both. The level of 2.2 ppm of copper per pound of feed is adding
about 25 per cent of the horse's need in the ration. Copper, as well as iron, are
very important in hemoglobin formation. A lack of either one causes anemia.
The pig's requirements are about 80 ppm. The iron requirements of beef cattle
are not known and it is thought that the requirement for the horse is less than 40
ppm. Thus, the level of 11 ppm in the ration will supply about one-fourth of the
daily needs of the horse assuming his iron requirements are about 40 ppm. Iron
injections have been shown to be very helpful in preventing anemia with the pig.
Research is needed to determine whether iron injections might help the very young
foal since horse milk is also low in iron.
The pig's requirements are about 0.2 ppm in the ration. The requirements for
the horse are probably similar to this. Only a stabilized source of iodine should
be added to the ration. Iodine is readily destroyed or oxidized, and thus one needs
to be very careful in making sure a stable source of iodine is used. Since iodine
is so easily destroyed, about 2 1/2 times the daily requirement is being added. A
lack of iodine causes foals to be stillborn or weak.
The manganese requirements for the pig are 20 ppm. The requirements for beef
cattle are uncertain and for the horse they are unknown. Using the pig's require-
ments as a guide, a level of 11 ppm of manganese in the feed is being recommended.
This level will supply about one-half of the horse's manganese requirements (if
one assumes the horse's requirements are similar to those of the pig). Manganese
is concerned with proper bone formation and reproduction in the pig. It should
probably be assumed that it has the same function with the horse until such time
as research information defines the role of manganese in horse nutrition.
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The pig's requirement for zinc is 50 ppm, but the horse's requirements are not
known. Using the pig's zinc requirements as a guide, a level of 50 ppm in the
ration is recommended. This level will supply the horse's needs assuming his re-
quirements are similar to those of the pig. Excess calcium increases the need for
zinc in the pig. It is reasonable to assume that it will also have the same effect
with the horse. Thus, the entire amount of zinc needed is added to the ration to
protect against a possible higher need by excess calcium. Zinc is very important
for a good healthy skin and hair coat.
The requirements for cobalt by beef cattle are about 6.6 to 11 ppm in the ration.
It is doubtful if cobalt will benefit the pig if the ration contains enough vitamin
B12. Horses have successfully grazed pastures so low in cobalt that ruminants died
when exclusively confined to them. Thus, the requirement for the horse is probably
less than 0.05 ppm of cobalt in the ration.
The effect of cobalt seems to be related to vitamin B12 synthesis by the ani-
mal. B12 contains cobalt in its molecule. Thus, without cobalt the animal cannot
synthesize B12. Since vitamin B12 will relieve cobalt deficiency symptoms, it is
very possible that cobalt is not needed by livestock if the ration contains an
adequate level of B12.
Since horse rations might be borderline or low in B12, it is a good idea to
add cobalt to the ration. The level suggested in Table 7 would add about the daily
cobalt requirement for the horse.
Other mineral elements
As far as is now known, there is no need to add potassium, magnesium, selenium
and sulfur to horse rations.
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The writer has observed a great deal of variation in the feeding of minerals
to horses. A good many of the Thoroughbred breeders do not self-feed minerals to
their horses. They all .add minerals to the ration, however, but the levels used
vary considerably. Moreover, a good deal of minerals are also added in high quality
feeds such as Calf Hanna, Sho Glo and others which are added in varying levels to
horse rations. The net result is that the level of minerals contained in horse ra-
tions varies a great deal. In many cases, certian mineral elements may be over-
fed, whereas others may be under-fed. Imbalances of minerals may also occur in some
The writer feels that horses should be self-fed minerals in addition to the
minerals added in the ration. This could be a complete mineral mixture in one com-
partment and salt in the other compartment of a mineral box. This would allow the
horse the choice of feeding on salt or the complete mineral mix if it needed extra
minerals. Much needs to be learned about mineral mixtures, as well as the types of
mineral boxes to use, for self-feeding to horses. Some horses will not eat salt if
it has the trace minerals added. Thus, trace mineralized salt or complete mineral
mixtures need to be made palatable enough for the horse to consume them in proper
amounts. Palatability needs to be controlled, however, so that the horses do not
over-consume minerals to the point where harmful effects can be obtained. It is
always a good idea to add one per cent of salt and one per cent of a calcium and/or
phosphorus source to concentrate rations as a means of force feeding about the de-
sired amount of these minerals in the ration. This becomes diluted to 1/2 per cent
of each in the total ration since concentrates, in general, make up about half the
total feed intake. Self-feeding of additional minerals is just insurance against
a possible need in case the amount consumed in the ration is not adequate.