Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

CHAPTER 4
heavy louse infestation, may cause excessive grooming
and the presence of more lick marks than normal.
Repeated rubbing can lead to hair loss and thickening
of the skin. The presence of any obvious abnormalities,
including swellings or discharging abscesses,
should be noted for further investigation
later. Damp areas caused by sweating may be seen in
pyrexic animals and in warm weather. Skin loss
through injury may be seen. Gangrenous changes in
the skin and deeper tissue may have arisen through
loss of circulation and may be seen or noted during
manual appraisal of the skin.
Manual appraisal of the skin
This should involve as much of the body surface
as possible, using caution when touching sensitive
areas which might cause the animal to kick. Manual
appraisal will enable the clinician to detect lesions
which are not immediately visible, for example beneath
matted hair. Any abnormalities detected are
subjected to further scrutiny which may necessitate
removal of hair and examination of the skin in good
light with the aid of a hand lens. Enlargement of
lymph nodes may be detected at this stage (see
below). The thickness of the skin and the presence of
any subcutaneous oedema or infection should also
be noted. The average skin thickness in adult cattle is
6 mm, with decreasing thickness being evident from
the dorsal to the ventral body surfaces. The skin over
the brisket is quite thick and mobile. This area of skin
may have a spongy texture when compressed and
may give an impression of subcutaneous oedema although
it does not pit on pressure. Genuine oedema
which does pit on pressure may be seen in this area
and between the mandibles in cases of right sided
cardiac failure. The skin covering the lower limbs is
relatively immobile.
Manual examination of the skin will also allow assessment
of skin turgor – its resilience and flexibility.
Picking up a skin fold between finger and thumb and
releasing it provides a general assessment of the animal’s
state of hydration. In a well hydrated animal
the pinched skin falls immediately back into place; in
a dehydrated animal the return to normal is delayed.
The best site for this test is the skin of the upper
eyelid.
Pathological thickening of the skin occurs in a number
of skin conditions, including sarcoptic mange. Thickening
in the form of callus formation can occur in areas
of skin, including those covering joints, which are
repeatedly subjected to trauma. Examples include
the elbows and hocks in animals with poor bedding.
Distribution of skin lesions
This is of diagnostic importance. Lesions caused by
photosensitisation are commonly seen in lightly pigmented
areas on the dorsal parts of the body which
are exposed to sunlight. Such lesions are not normally
seen in pigmented areas. Ringworm lesions
in calves are particularly common on the head and
neck, but also occur elsewhere.
Description of the skin lesions
The clinician should try to determine exactly what
abnormalities are present in the skin, which tissues
are involved and how deeply the disease process
extends into and over the skin. The larger external
parasites such as lice may be seen at this stage. Skin
temperature, thickness, consistency and colour are
observed and compared with adjacent areas. The
presence of subcutaneous oedema or increased skin
turgor is noted: these abnormalities may be caused
by hypoproteinaemia or heart failure and dehydration,
respectively, but they can also be the result of
local pathology. When numbers of skin lesions are
found it is important to determine if they share the
same aetiology. They may represent different stages
of one disease process. More than one condition can
be present at the same time.
There may be abnormalities in the sebaceous and
sweat glands or gross proliferation of the superficial
layers. Self-inflicted trauma can greatly modify and
mask the clinical picture. Skin abnormalities may
involve some or all of the component structures of
the skin: the hair, follicles, epidermal, dermal and
subcutaneous tissues.
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