Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

CHAPTER 5
Figure 5.13 Use of Young’s gag to open a bullock’s
mouth. Note the central pair of permanent incisor teeth in
this animal aged 1 year 9 months.
be caused by excessive muscular activity such as is
seen in trismus which may occur in tetanus and sometimes
in hypomagnesaemia. Damage to the temperomandibular
joint or degenerative changes affecting
its articular surfaces may also result in an inability to
open the mouth. Malocclusion of the upper and lower
jaws is seen occasionally as a result of developmental
abnormality.
Neurological lesions affecting prehension, mastication
and swallowing of food may occur and should
be evaluated if difficulty in completing these functions
is detected.
Inability to co-ordinate lip movements may occur
through damage to the 7th cranial (facial) nerve. This
may be unilateral or less commonly bilateral. Accumulation
of food boluses in the cheeks may also be seen.
Facial nerve damage may occur through injury to the
nerve and surrounding tissues. It is also seen in some
cases of listeriosis (Fig. 5.6).
Inability to move the tongue may arise through
damage to the 12th cranial (hypoglossal) nerve. This
may be the result of alkaloid toxicity, botulism or in
listeriosis.
Inability to swallow may arise through dysfunction
of the 9th cranial (glossopharyngeal) nerve and also
the 10th cranial (vagus) nerve. Such problems may
arise through local damage to nerves by abscess or
tumour formation adjacent to the nerves or in the
medulla. Damage may also be seen in listeriosis.
All visible areas of the mucosa including the dental
pad should be inspected for signs of ulceration or
damage. The buccal mucosa which lines the cheeks
should be carefully checked – especially in calves –
for the presence of diphtheritic membranes which are
visible adjacent to the cheek teeth in some cases of
calf diphtheria (necrotic stomatitis) (Fig. 5.14). A
good light is essential for this examination. The buccal
mucosa can also be a site for vesicles of foot-andmouth
disease.
The dental pad replaces the incisor teeth in the
upper jaw of cattle. It is covered with mucosa but is
quite firm and fibrous. In adult cattle it may show
small scars sustained when the animal was grazing.
It can also be the site for lesions of a number of diseases
including bovine papular stomatitis, bovine
virus diarrhoea, and foot-and-mouth disease.
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