Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

CHAPTER 8
Clinical Examination of the
Gastrointestinal System
This chapter describes the clinical examination of the
gastrointestinal system, the peritoneum, the umbilicus
and the liver. Examination of the mouth, pharynx
and oesophagus is decribed in Chapter 5. Examination
of the adult and calf are described separately.
Applied anatomy
The gastrointestinal system within the abdomen is
composed of the forestomachs, the small intestine
and the large intestine. The forestomachs are composed
of the reticulum, rumen, omasum and abomasum.
These structures are shown in Fig. 8.1. The
development of the newborn calf from a functional
monogastric animal to a ruminant is illustrated by
the increase in volume of the rumen relative to the
abomasum with age as shown in Table 8.1. The adult
pattern of ruminal movement is established between
6 and 8 weeks of age. The oesophageal groove
crosses the reticulum and when closed forms a tube
which enables ingesta to bypass the rumen. The
forestomachs in adult cattle have a volume in the region
of 150 litres with the relative proportions being
rumen 70 to 80%, reticulum 5%, omasum 8% and the
abomasum 7 to 15%. In the normal adult the rumen
fluid has a pH of 5.5 to 7.0 depending upon the diet.
Cattle fed high levels of concentrates will have a
lower pH than animals fed on a roughage diet. The
abomasum has a normal pH range of 2.0 to 4.0. The
small intestine is composed of the duodenum, the
jejunum and the ileum. It enters the large intestine
at the ileocaecocolic junction. The large intestine is
composed of the caecum, colon (ascending, spiral
and descending) and rectum. Other structures in the
abdomen are the lesser omentum, greater omentum,
liver, spleen and urogenital system.
The rumen and reticulum after feeding occupy the
entire left part of the abdominal cavity, extending
from the diaphragm at about the 7th rib to the pelvis.
The reticulum lies medial to the 6th to 8th ribs on the
left side with the anterior wall at about the level of the
elbow. The spleen lies on the anteriolateral aspect of
the left side of the rumen beneath the last four ribs;
this is shown in Fig. 8.2. The omasum lies in the lower
part of the right anterior abdomen between the reticulum
and anterior rumen to the left and the liver on
the right, opposite ribs 7 to 11. The abomasum lies
largely on the abdominal floor at about the midline or
just to the right side, with the pylorus at about the
level of the ventral end of the 11th or 12th rib. The
liver is situated on the right side of the anterior abdomen
against the diaphragm opposite the upper
part of the last three ribs. The rest of the right side of
the abdomen is occupied by the small and large intestines
within the omentum. These structures are
shown in Fig. 8.3. The left kidney is displaced by the
rumen to the right side of the sublumbar region
beneath the 3rd to 5th lumbar vertebrae. The right
kidney is anterior to the left and lies ventral to the last
rib and first two lumbar transverse processes, with
the anterior pole surrounded by the liver.
Normal behaviour and physiology
In calves, a balanced diet regarding the quantitiy and
quality of fibre and concentrate is required to ensure
normal anatomical and functional development of
the rumen. Proliferation of the mucosal tissue and
ruminal pupillae is dependent upon the production
of butyric acid and to a lesser extent propionic acid.
Roughage stimulates the growth in volume of the
reticulum and rumen and the development of the
muscle layers. Incorrect diet can result in a dysfunctional
rumen.
Adult cattle ruminate for a total of 8 hours daily:
there are between four and 24 ruminating periods,
with each period lasting 10 to 60 minutes. There are
360 to 790 regurgitated boluses produced a day with
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