Correct dentition is of
critical importance to the maintenance of body condition/weight
gain in adult sheep. Premature loss of incisor teeth (broken mouth)
is a major problem leading to early involuntary culling because
affected sheep are unable to bite off short and/ or rough pasture
leading to malnutrition, poor production and weight loss.
Overgrown, worn and absent molar teeth cause problems with
mastication of fibrous feeds and subsequent weight loss.
Fig 1: Correct
dentition is essential for sheep grazing rough
Fig 2: Molar
teeth cause problems with mastication of fibrous feeds and
subsequent weight loss. Note the swollen cheeks in this Cheviot
Fig 3: Molar
teeth lesions cause problems with mastication of fibrous feeds.
Note the sunken flanks suggestive of poor feed
Sheep have 32 permanent teeth
with a dental formula of 2(incisors 0/4, premolars 3/3, and molars
3/3). The temporary incisor teeth erupt sequentially at
approximately weekly intervals from birth. The three temporary
premolars erupt within two to six weeks. The permanent central pair
of incisors erupt at 15 months and are in wear by 18 months; the
other permanent incisors follow sequentially at six months'
intervals. The first permanent molar erupts at three and five
months in the lower and upper jaws, respectively. The second
permanent molar erupts at nine to 12 months, and the third
permanent molar and permanent premolars erupt between 18 and 24
Incisor teeth alignment
Examination of incisor teeth
alignment is performed by running an index finger along the dental
pad,with the sheep's mouth closed and the head held in the normal
resting position. This examination will reveal any teeth projecting
forward of the normal contact on the dental pad (overshot jaw or
prognathia; a very common hereditary defect in Blueface Leicester)
or behind (undershot jaw or brachygnathia).
Fig 4: Undershot
jaw or brachygnathia in an adult Scottish Blackface
Sheep with such incisor teeth
mal-alignment with the dental pad should be culled as fat lambs but
it is surprising how many sheep are kept as breeding stock despite
such teeth problems.
Fig 5: Undershot
jaw or brachygnathia in the adult Scottish Blackface ewe shown
Incisor loss (broken mouth)
Premature loss of incisor
teeth is a major problem that leads to early culling because
affected sheep are unable to bite short pasture leading to
malnutrition, poor production and weight loss particularly on
marginal grazing and hill pastures. Traditionally in the UK,
culling for reproductive reasons follows six crops of lambs but
incisor tooth loss may affect two-crop ewes on some farms
representing major production and financial losses.
Fig 6: Ewe with
considerable incisor teeth wear and four missing
Incisor teeth loss is readily
recognised during checks for correct dentition undertaken routinely
as part of the selection procedure pre-mating. The incisor teeth
develop an elongated appearance, become loose, and are eventually
There are no recognised
control measures for broken mouth. Management factors include
drafting broken-mouthed ewes to lowground pastures where these ewes
can be as productive as full-mouthed ewes provided there is an
appropriate sward height and/or supplementary concentrate
Dentigerous cysts occur very
sporadically in young adult sheep. Malocclusion leads to weight
loss and poor body condition.
The cause of these cysts
remains unknown. Sheep aged two to four years are typically
affected and may present in poor body condition if grazing has been
sparse for some months. There is a uniform, non painful, bony
swelling of the mandibular symphysis about 5 6 cms in diameter
which involves the roots of the incisor teeth. Some of the incisor
teeth may have been lost whilst the remaining incisor teeth are
often aligned horizontally.
There are no recognised
control measures for this sporadic condition. Affected ewes should
be managed in a similar manner to broken-mouthed sheep with
preferential grazing and supplementary feeding.
Cheek teeth problems
Excessive premolar and molar
teeth wear, leading to malocclusion and poor mastication of fibrous
food, is a major cause of weight loss and poor condition in older
sheep. Very sharp enamel ridges develop on the outer aspect of the
upper cheek teeth, and the inner aspect of the lower cheek teeth,
due to lack of wear on these tooth margins. Cheek tooth loss can
occur with consequent unimpaired growth of the opposite tooth into
this gap leading to a step mouth.
Cheek teeth problems tend to
be of greater significance than incisor teeth loss due to loss of
their grinding function of fibrous feedstuffs. Cheek teeth problems
can best be identified by impaction of food in the cheek(s) and
short jerky jaw movements with the mouth held slightly open. When
eating, sheep with molar teeth problems often have pieces of
fibrous feed protruding from the corners of the mouth and
frequently drop large wads of masticated fibrous food from the
Fig 7: Sheep with
molar teeth problems often have pieces of fibrous feed protruding
from the corners of the mouth when eating. Click photo for video or
see video at www.nadis.org.uk
Sheep with severe teeth
lesions often drop pelleted feed when eating and may raise their
head while masticating to assist movement of food over the dorsum
of the tongue and into the pharynx.
Fig 8: Ram with
molar teeth problems unable to masticate fibrous
Fig 9: Samples
collected at necropsy from the rumen of normal sheep have much
shorter fibre length (left) than samples from sheep with molar
dentition problems (right).
Sheep with molar dentition
problems are unable to grind fibrous feed sufficiently to allow
further digestion in the forestomachs. Samples collected at
necropsy from the rumen of normal sheep have much shorter fibre
length than samples from sheep with molar dentition problems
illustrating the problems caused by poor mastication of fibrous
Careful palpation of the
dental arcade through the cheek reveals the sharp irregular ridges
of the outer aspect of the upper cheek teeth, and any lost upper
cheek teeth. Examination of the molar teeth with a gag and torch
will confirm these findings.
Fig 10: Loss of
premolar and molar teeth. Unopposed wear has resulted in overgrowth
and a stepped mouth in this sheep.
Bony lesions of the jaw bone
(mandible ) associated with cheek tooth loss that may suggest tooth
root infection are uncommon.
Infection of the left mandible associated with an infected tooth
root in a Texel ram.
There is no treatment and
affected sheep should be culled although their body condition can
be improved by 1.5 to 2 units of condition score following generous
concentrate feeding (up to 1.5 kg daily) over a 10 to 12 week
period which would command a much better slaughter price. Care must
be taken to avoid problems with acidosis when concentrates are
first introduced into the ration.