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:

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.