Vitamin deficiencies
Introduction
The important vitamins for survival and growth of
grazing animals are either manufactured in the rumen by the rumen microbes, in
the body from sunlight, or are stored in sufficient quantity in the liver or
contained in adequate amounts in available feed.
Even under drought conditions, grazing animals almost
never require expensive vitamin supplements or injections. In ruminant diseases, only fat
soluble vitamins A, D and E have a real importance.
Vitamin
A
Vitamin A itself does not occur in plants, but its
precursor carotene in green plant material is converted in an animal's body to
vitamin A.
Green pasture, tree or shrub leaves, hay with good
green colour and yellow maize all contain sufficient carotene to allow the
animal to produce enough vitamin A to top up the reserves stored in the liver.
These reserves are readily available for use by the animal, even during
drought, and will compensate for any dietary inadequacy; supplementary vitamin
A is not generally required.
For a vitamin A deficiency to occur, the diet would
need to be completely devoid of green plant material for a considerable period
of time. As little as 28 g of green material per day will provide the animal's
vitamin A requirements almost indefinitely. This can be obtained from any green
plant material, including browse leaves and shrubs.
Adult wethers or ewes and cattle can store sufficient
vitamin A in the liver to provide for a period in excess of one year with no
access to any green plant material (at all), including mulga and other fodder
trees or browsed leaves.
There is no evidence available to indicate that sheep
wholly or largely eating scrub require vitamin A supplementation. One possible
exception is rams and perhaps bulls required for breeding after some months on
dry pasture containing no green material. The fertility of rams is seriously
reduced after they have been without any green feed for 2-6 months. Rams that
are to be used for breeding and that have not had access to any green feed or
leaves for 2-6 months should be given 1,000,000 I.U. (International Units) of
vitamin A, a minimum of 6-8 weeks before joining, if there is no green feed
available at the time.
A second possible exception is lambs and calves weaned
from drought-affected mothers with depleted liver stores. Lambs and weaners
that have been reared without any access to green feed or tree leaves for 3-4
months should be supplemented with 500,000 I.U. of vitamin A from the cheapest
source available; 350,000 I.U. is sufficient for lambs. These amounts will give
a high degree of protection for the subsequent 6 months, improving survival,
growth and wool production.
Where administration of vitamin A is necessary, use
the cheapest form available.
There is no evidence available to show the superiority
of injecting vitamin A over drenching with vitamin A.
On the one hand injection gives quicker and slightly
higher liver storage, while drenching results in similar levels fairly quickly.
Over the long term, neither method of administration
has shown to have an advantage over the other in vitamin A storage or
utilization. For drenching purposes, oil base, emulsion, and water-soluble
forms of vitamin A are equally effective.
It may be advisable to give vitamin A to sheep and cattle
given high-energy diets with little green feed in feedlots if they have been
brought in after 3 or 4 months on dry feed; the recommended dose is about 1
million I.U. for cattle and 100,000 I.U. for sheep.
The supplement will generally not be necessary if the
animals have been brought in from green pasture because their requirements not
met by feed will probably be provided from reserves in the liver.
Clinical signs of Vitamin A
deficiency:
Includes the following:
Includes the following:
1. Decreased appetite
leading to reduced growth
2. Impaired night vision
3. Increased still births
in pregnant animals due to affected reproductive function especially in cases
where dry cows are offered poor diets
4. Fainting fits in
calves: the calf collapses as if in a deep sleep then gets up and walks away
quite normally
5. In latter stages of
deficiency, bone growth is affected and this may cause pressure on the nerves
to the eye which may lead to total blindness
Diagnosis of Vitamin A deficiency
This can be one by investigating the
history of animals and their diets, analysis of blood and liver samples in a
laboratory.
Vitamin
D
There is
little vitamin D in plants and animals obtain most of it by synthesizing the
vitamin in the skin by action of ultra-violet rays from the sun. It is involved
in the absorption of calcium and phosphorous from the intestines and the
deposition of the minerals in bone together with maintenance of normal blood
levels. Vitamin D deficiency in young calves is likely to occur when they are
housed in houses with dim lights and offered poor quality diets.
The body also stores sufficient vitamin D to overcome dietary deficiency for
several months. Supplementation of drought or feedlot rations is unnecessary.
Vitamin D deficiencies only occur occasionally in the southern areas of Australia.
Clinical signs of
Vitamin D deficiency
Includes the following:
1. Reduced growth rates
2. The legs may be bent
and swollen with abnormal swellings with stiffness and lameness in a number of
animals
3. The teeth may be pitted
out of line and the jaw bone deformed
Treatment
Is done by
injecting vitamin D and by correcting the ration, which may include oral
supplementation with vitamin D.
Vitamin K
This is
synthesized by the ruminal microorganisms and
is available in leafy forages in plenty. Primary deficiency does not occur
though can be induced by the action of dicoumarol poisoning such as warfarin
rat poison and mouldy clover hay which inhibit the action of vitamin K. Vitamin
K is involved in blood-clotting mechanisms.
Clinical signs of vitamin
K deficiency
Include
the following:
1.
Failure of blood clotting including excessive bleeding from
cuts
2.
Appearance of large red hemorrhagic areas in the membranes of
the mouth, eyes and nose
3.
Abdominal pain and lameness
Treatment and
prevention
1. To identify and remove
the source of poison
2. Give vitamin K by mouth
or through injection.
Vitamin
E
Vitamin E is contained in green plant material, hay
and grain; the concentration in grain decreases during storage.
There are currently no confirmed reports of vitamin E
deficiency in cattle and deficiencies in sheep are rare.
Vitamin
B
This group of
vitamins is synthesized by micro-organisms in the rumen and any excess is
absorbed by the cow. They are also present in ample quantities in milk and
therefore primary dietary deficiency is never seen.
Vitamin C
This is
produced in tissues of all farm livestock and dietary supply is unnecessary.
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