The clinical signs associated with trace element
deficiency in sheep are often insidious in onset and usually
present as poorly grown lambs during late summer/early autumn.
There is considerable interplay between parasitic gastroenteritis
(PGE) and trace element deficiency states such that it is important
for the farmer and veterinary practitioner to consider and deal
with both problems.
The trace element deficiency
states generally considered are: cobalt, copper, and vitamin E and
Fig 1: Poor quality wool with an open fleece, small
size and poor body condition caused by cobalt deficiency in weaned
Cobalt has an important
biological role as a constituent of vitamin B12 which is
manufactured by micro-organisms in the first stomach (rumen).
Cobalt deficiency (pine) occurs where there are low soil cobalt
concentrations which may be further complicated by PGE which causes
diarrhoea thereby interfering with the absorption of vitamin
Fig 2: Pine and parasitic gastroenteritis causing
emaciation in five month-old weaned lambs.
Clinical signs of cobalt
deficiency are most commonly observed in weaned lambs at pasture
during late summer/autumn. Signs include lethargy, reduced
appetite, poor quality wool with an open fleece, small size and
poor body condition despite adequate nutrition. There may be tear
staining of the cheeks, and pale mucous membranes (eyes) develop
after several months. Cobalt-deficient sheep may fail to respond
well to vaccinations and be more susceptible to clostridial
diseases (for example pulpy kidney) and pasteurellosis
In severe cases of cobalt
deficiency (referred to as ovine white liver syndrome) lambs
present with nervous signs including depression, head pressing, and
Cobalt deficiency is much
less common in adults but is reported to cause reduced fertility
and poor mothering ability but these signs may be more related to
generalised low body condition scores.
Fig 3: Pine causing poor growth in weaned
There is considerable
interaction between chronic parasitism and trace element deficiency
states such that it may prove difficult to ascertain which is the
more important condition. Diagnosis is often compounded by the fact
lambs may have been recently treated with an anthelminitic and
moved onto better pasture immediately before veterinary
Fig 4: Severe cobalt deficiency.
The main differential diagnoses for cobalt pine your
veterinary practitioner will consider include:
nutrition/overstocked pasture mean that lambs do not grow
pasture after weaning.
Coccidiosis and/or severe
nematodirosis can cause a serious growth check often around 6 to 8
weeks-old with protracted convalescence.
is a very common cause of poor lamb growth
Fig 5: Severe cobalt deficiency causing depression
and head pressing.
Diagnosis is based upon
clinical signs in areas with known cobalt-deficient soils supported
by specific diagnostic tests undertaken by the farmer's veterinary
surgeon including low plasma and/or liver vitamin B12
concentrations. As a general guide, a positive growth response to
supplementation is expected if the mean plasma vitamin B12
concentration is < 500pg/ml, and is likely to be significant
where it had been below 250pg/ml. A minimum of 10 blood samples is
recommended to determine the mean plasma vitamin B12 concentration
but this number is likely to be limited by cost considerations.
These blood samples must be collected as soon as possible after the
sheep have been gathered as values increase significantly within
hours of confinement.
The veterinary practitioner
may advise a supplementation trial whereby growth rates of
supplemented and control lambs are measured over eight to 10 weeks
and. Typically, a 4 to 6 kg improvement in growth rate over
controls would be expected over eight to 10 weeks of
supplementation. Where cobalt deficiency is suspected, 10 to 12
lambs could be left untreated until such time as a demonstrable
difference could be appreciated thereby reducing the impact of
leaving lambs without cobalt supplementation.
Fig 6: Parasitic gastro-enteritis is a very common
cause of poor lamb growth
Treatment is more quickly
effected by a combination of intramuscular injection of vitamin B12
and drenching with up to 1 mg/kg bodyweight of cobalt sulphate.
Thereafter, monthly drenching with cobalt sulphate, often in
combination with an anthelmintic preparation, should ensure
Oral cobalt supplementation
is very cheap indeed and, where appropriate, can be added to
certain anthelmintic drenches. Monthly dosing lambs from around
three months-old with cobalt drenches should supply sufficient
cobalt to growing lambs in most situations.
Cobalt containing boluses,
which lodge in the reticulum (second stomach), provide a continuous
supply of cobalt but are expensive in those lambs which require
supplementation for only two to three months.
Soluble glass boluses
containing cobalt, selenium and copper are an expensive means of
supplying cobalt and are only indicated in situations where all
deficiency conditions are considered to exert a negative influence
Fig 7: Monthly dosing lambs from around three
month-old with cobalt drenches should supply sufficient cobalt to
growing lambs in most situations.
Oral cobalt supplementation
costs less than 1 penny per 25 kg lamb. Production losses from poor
growth and delays to marketing may cost £10-£15 per
Fig 8: Swayback causing
hind leg weakness in a young lamb.
Copper deficiency is common
when sheep graze pastures low in copper but more often high in
iron, molybdenum and sulphur. Where two or more of these three
elements exist together on a farm, in quite 'normal'
concentrations, they will act synergistically to bind out copper
from a diet. The clinical manifestation of copper deficiency varies
worldwide with swayback more common in the UK, poor wool quality
and anaemia in Australia, and poor bone mineralization in New
As well as being susceptible
to copper deficiency, sheep are also prone to copper accumulation
and toxicity. There is considerable breed variation with respect to
copper absorption and therefore to copper deficiency and toxicity.
Veterinary advice is essential before copper supplementation to
Fig 9: Copper poisoning -
timing and type of copper supplementation must be specified in the
farm's veterinary flock plan
Copper deficiency in ewes
during mid-pregnancy may lead to swayback in lambs.
In growing lambs copper
deficiency may result in a poor fleece without its natural "crimp"
which has been described as "steely wool". Poor growth, anaemia,
and increased susceptibility to bacterial infections has been
reported but is much less common in the UK.
Swayback is provisionally
diagnosed by the veterinary practitioner on clinical examination
and confirmed following histopathological examination of the
central nervous system.
Copper deficiency is most
reliably diagnosed in growing lambs based upon a dose/response
study (see above under cobalt supplementation noting veterinary
advice is essential before giving copper supplements).
Plasma samples are most
commonly submitted for laboratory analysis by the veterinary
practitioner with concentrations below 9.4 μmol/L
indicating depletion of liver reserves. It is reported that
lamb growth rates are not adversely affected until plasma
concentrations fall below 3 μmol/L.
Differential diagnoses include vertebral body empyema (spinal
abscess) and sarcocystosis.
Prevention of copper
deficiency in growing lambs is much more important than treatment
because irreversible changes have often taken place in the fleece,
and full compensatory growth may not result after supplementation.
Furthermore, treatment of swayback is hopeless and emphasis must be
placed upon preventive measures.
While copper deficiency is
often a perennial problem on certain farms, farmers must always be
made aware of the risks of copper toxicity. Therefore timing and
type of copper supplementation must be specified in the farm's
veterinary flock plan with specific notes made regarding no other
source of extra copper. Sheep must not be given a copper supplement
prior to, or during, housing. Toxicity could result from a number
of sources including using more than one method of copper
supplementation, and use of feeds with high copper
Copper is usually given by
injection as copper heptonate. Certain copper injections are
irritant and may cause a localised reaction. Care must be exercised
that the injection is given correctly because abscessation, and in
some cases tracking of infection to the spinal canal, have been
observed after incorrect injection technique
Supplementation with copper
oxide needles can be administered orally in a gelatin capsule.
Sheep should not be re-treated for 12 months unless signs of copper
of the ewe during mid-gestation will prevent the development of
swayback in her newborn progeny.
Copper supplementation costs
between 30 pence to £1 for injectable preparations and gelatin
capsules containing copper oxide needles, respectively.
Fig 10: White muscle
disease affecting a rapidly growing two week-old
Selenium and vitamin E deficiency
Often referred to as white
muscle disease, nutritional muscular dystrophy, and stiff lamb
White muscle disease occurs
in the UK with recognised risk factors such as feeding home grown
cereals and root crops, and incorrectly mineralised rations;
however the disease prevalence is generally low. Selenium
deficiency occurs in soils of certain geographic areas world-wide
leading to pasture/crop deficiency. Vitamin E concentrations are
high in green crops but fall rapidly under drought conditions.
Certain root crops are known to be low in both selenium and vitamin
E. Feeding grain treated with propionic acid may increase the risk
of white muscle disease.
In the UK, white muscle
disease typically affects rapidly-growing two to six week-old
lambs; often ram lambs of meat breeds such as the Suffolk and
Texel. There is sudden onset stiffness with lambs reluctant to move
such that they are easily caught. After one or two days, affected
lambs are unable to rise.
growth in lambs has been reported in certain geographic areas of
Australia and New Zealand where dramatic improvements have resulted
after supplementation. Improved lamb growth rates after selenium
supplementation are less commonly reported in the UK but will
depend upon soil type and localised problems may exist.
Early embryonic loss/failure
to implant after mating has been attributed to selenium deficiency.
In ewes an increased lamb crop with fewer barren ewes has been
reported after selenium supplementation before the mating period
but these responses were highly variable between flocks.
The main differential diagnosis for stiffness leading to
recumbency in lambs less than two weeks-old is bacterial infection
of a joint in the neck and it is very important that this problem
is investigated by a veterinary practitioner.
There are many causes of poor
growth in groups of growing lambs including cobalt deficiency, poor
pasture management, and parasitic gastro-enteritis. Likewise there
are many causes of returns to service including infertile rams
(ewes returning at 17 day intervals), toxoplasmosis and Border
disease (ewes returning at intervals greater than 17
A provisional diagnosis of
white muscle disease in young lambs is based upon clinical signs in
rapidly growing healthy lambs with the presence of some of the risk
factors listed above. Muscle enzyme concentrations will be measured
by the veterinary practitioner. Most laboratories determine
glutathione peroxidase as the indicator of selenium
subcutaneous injection of young lambs suffering from white muscle
disease with 0.75 to 1.5 mg selenium as potassium selenate and 34
to 68 mg vitamin E (dl a-tocopherol acetate) results
in return to full mobility within two to three
A range of methods can be
used to supply selenium and/or vitamin E including in-feed
medication, periodic drenching, depot injection, and intraruminal
glass bolus or pellet. It is generally accepted that free-access
licks/minerals are unreliable because of highly variable
As white muscle disease is
seen most commonly in young lambs, prevention can be achieved by
supplementation of the dam's ration during late gestation or
injection of all newborn lambs with a selenium and vitamin E
Supplementation of growing
lambs is best achieved by drenching, often in combination with
anthelmintic treatment. Such supplementation provides adequate
selenium for one to three months. Great care must be exercised when
formulating a supplementation programme because toxicity can occur
following over-dosage especially in young lambs. The preparation
must be shaken vigorously prior to use to ensure thorough mixing.
In breeding sheep, selenium supplementation via drenching is given
one to two months before the start of the breeding season. It is
essential that veterinary advice is obtained before
Intraruminal glass boluses
are a very expensive means of supplementing with selenium but is a
useful method where other trace element deficiency states occur
In the absence of a split
flock trial, it is very difficult to calculate the cost benefit of
selenium supplementation with respect to reproductive wastage. If
doubts exist regarding poor reproductive performance, ewes should
be drenched at regular intervals prior to mating.