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Vitamin A deficiency
Vitamin A is not found as such in grass: sheep make it from carotene, the orange pigment in green plants. Fresh grass and well-preserved fodder are rich in it. It is essential for vision, the quality of the mucous membranes which line the r...
What is it?
Vitamin A is not found as such in grass: sheep make it from carotene, the orange pigment in green plants. Fresh grass and well-preserved fodder are rich in it.
It is essential for vision, the quality of the mucous membranes which line the respiratory and digestive tracts, bone growth and reproduction.
The liver constitutes a reserve which lasts for several months: this is why the deficiency never appears straight away, but after a long period without greenery. Prolonged droughts, winters spent only on straw and aged fodder, years without regrowth are the typical circumstances in Mediterranean livestock farming.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Difficulty finding direction at the end of the day or at the entrance to the building: animals hesitate, stumble, bump into obstacles, stay behind even though they normally move around in full sun.
At a more advanced stage: loss of vision, including during the day, animals that get lost and no longer follow the herd.
Watery eyes, runny eyes, cornea that becomes cloudy or dry in appearance.
Dull, dry wool, peeling skin.
Lambs whose growth stagnates, despite an apparently correct ration.
Runny nose, cough, repeated respiratory episodes in the herd: weakened mucous membranes do not defend well against microbes.
Diarrhea that persists in young people.
In ewes: abortions, stillborn or weak lambs, sometimes lambs born with malformations, particularly of the eyes.
In rams: reduced fertility.
Nervous signs can appear in young people due to nerve damage, with uncertain gait and convulsions in severe forms.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Long period without green plants: prolonged drought, burned pastures, diet based on straw, stubble and fodder stored for a long time.
Fodder loses its carotene with time, heat and sun: two-year-old, yellowed hay no longer provides much, even if it appears healthy.
Rations based on cereals and by-products without vitamin supplements.
Liver reserves already started at the start of the difficult period, particularly in animals that had little grazing the previous year.
Increased requirements in growing young, pregnant and lactating females.
Liver diseases and parasitism, which reduce the storage and use of the vitamin.
Years of drought and prolonged dry season ends, a common situation in livestock farming in the Maghreb and arid zones.
Winter or summer diet based on straw and old fodder, without greenery or supplements.
Hay harvested late, very yellowed, or stored in the open air and in the sun.
Fattening in buildings on a dry ration for several months.
Growing young and pregnant ewes.
Total absence of vitamin supplementation in herd management.
Parasitism and associated liver diseases.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian is first interested in the dietary history: how long have the animals had access to green plants, what fodder is distributed, how long has it been stored.
He performs an eye exam on several animals and tests their ability to move in dim light, which is much more revealing than an exam in broad daylight.
It rules out other causes of visual and ocular disorders in sheep: infectious eye diseases, nerve damage, other deficiencies, poisoning. Many of them are urgent and can be treated.
Blood tests measure vitamin A on several animals in the batch; the dosage on the liver of a dead or slaughtered animal is even more reliable.
The analysis of the fodder completes the evaluation and makes it possible to decide on a lasting correction of the ration.
Treatment
The correction is based on a supply of vitamin A, prescribed by the veterinarian, by injection for a rapid effect in animals already affected, or by a supplement adapted to the entire ration.
No quantity or rhythm should be decided alone: vitamin A is stored in the liver and prolonged excessive intake becomes toxic, with bone and liver damage.
Putting greenery or carotene-rich fodder back into the ration is the basic measure, when the season permits.
Animals that already have corneal damage require specific eye care.
Recovery is spectacular when the damage only concerns low light vision: the animals normally redirect within a few days.
On the other hand, loss of vision that has been present for a long time, with damage to the nerve of the eye, cannot be recovered: treatment prevents worsening but does not restore sight.
Lambs born with deformities cannot be corrected after the fact.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Anticipate periods without greenery: this is the only real lever, because the deficiency takes months to set in and therefore leaves time to act.
Take care in harvesting and storing fodder: mowing at the right stage, drying quickly, storing away from the sun. Green hay remains much richer than yellowed hay.
Provide vitamin supplementation during long periods of dry ration, on veterinary advice, particularly for growing young and pregnant ewes.
Provide access, when possible, to some green fodder or regrowth, even in small quantities.
Monitor the behavior of the herd at dusk: animals hesitating at the entrance to the building are a very early and free warning signal.
Control parasitism and liver condition.
Do not inject vitamins on your own initiative: repeated overdoses are dangerous.
Possible complications
Permanent blindness when the eye nerve is affected.
Ulcers and opacities of the cornea, sometimes with loss of the eye.
Repeated respiratory episodes, fragile mucous membranes opening the door to infections.
Abortions, stillborn lambs, lambs born with malformations, particularly eye defects.
Sustained growth retardation in young people.
Mortality of the most affected animals and significant economic losses during a dry season.
When to see a veterinarian
Animals bump into, hesitate or get lost in dim light when they normally move around during the day.
One or more animals seem to no longer see: consult without delay, some of the causes can be treated.
The eyes run or appear cloudy in several animals in the flock.
Your flock has not had access to greenery for several months and the young are no longer growing.
Lambs are born dead or with visible abnormalities.
Respiratory episodes recur regularly without an identified infectious cause.
Prognosis
Beginner forms, limited to vision in low light, correct themselves very well and quickly.
Old damage to the nerve of the eye is permanent: sight does not return, even after correction of the diet.
The consequences on reproduction and on the growth of a season's lambs are also irremediable.
At the herd level, the prognosis depends above all on anticipation: a deficiency corrected before the signs costs nothing, an established deficiency costs a season.
Frequently asked questions
My sheep can no longer see in the evening but very well during the day, is this serious?
This is the very first sign of a lack of vitamin A, and it is good news to spot it at this stage: the correction works very well as long as the eye nerve is not affected. Talk to the veterinarian without waiting for vision to decline in broad daylight.
My hay looks okay, could it still be lacking in vitamin A?
Yes. Forage can be healthy and clean while having lost almost all of its carotene. Yellowed hay, harvested late or stored for a long time in the sun, provides very little. Green color is a better indicator than overall appearance.
Can I inject vitamins into my sheep for peace of mind?
No, not on your own initiative. Vitamin A is stored in the liver and becomes toxic with repeated excessive intake. Supplementation is decided with the veterinarian, depending on the ration and the duration of the period without greenery.
After how long without green grass does the problem appear?
It generally takes several months, because the liver builds up reserves. This explains why the deficiency appears at the end of the dry season or after a long winter in the barn, and not from the first weeks of dry ration.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
ANSES — Agence nationale de sécurité sanitaire (France)
Content reviewed by the TunisieVet editorial team · Updated 11 August 2026
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