Clinical Examination of Farm Animals - CYF MEDICAL DISTRIBUTION

Clinical Examination of the Gastrointestinal System
tube into the ventral meatus. The tube is advanced to
the larynx. The tube is further advanced at the pause
following expiration. On passage through the larynx
the animal is usually observed to swallow. If there is
coughing and breathing sounds are detected at the
end of the tube, it should be withdrawn into the nostril
and advanced again. If the tube passes down the
oesophagus into the rumen, gas may escape which
has a characteristic odour if the end of the tube is
smelled. To confirm that the tube is in the rumen, an
assistant should blow forcefully down the tube and
the veterinary surgeon should auscultate the rumen
at the left sublumbar fossa for bubbling sounds as the
gas penetrates the rumen fluid. To obtain a sample of
rumen fluid negative pressure is applied to the end of
the tube with a stirrup pump or by sucking the end of
the tube. Free fluid may flow through the tube and be
collected. If this fails, the tube should be bent and
withdrawn and a sample decanted from the rumen
fluid in its distal end. Asample can be collected into a
universal sample pot. The only difference between
using a stomach tube and a nasogastric tube is that the
tube is advanced through the gagged mouth to the
larynx.
The equipment required to perform a rumenocentesis
includes clippers, surgical antiseptic, alcohol and
a 9 cm 18 BWG (1.20 mm) spinal needle with a stylet.
The rumen contains a dorsal gas cap, a fibrous raft
and fluid in the ventral sac. Asmall area of skin in the
left ventral quadrant of abdomen is surgically prepared.
To protect the operator, a tail kinch or an antikick
bar can be applied. The lumbar spinal needle is
thrust up to the hilt through the skin of the prepared
site into the fluid contained within the ventral sac. A
syringe is attached to the needle and a sample withdrawn.
Sometimes the needle can get blocked by
solid material and may have to be cleared by injecting
air. Once a sample has been obtained the needle is
withdrawn.
Rumen fluid analysis
Care with sampling is required as saliva contamination
increases the pH of the rumen sample. The sample
should be evaluated as soon as possible because
cooling and exposure to air alter protozoan and bacterial
activity.
Colour
Normal rumen fluid is usually olive green or greenish
brown. In ruminal acidosis the fluid may appear
milky grey.
pH
The rumen fluid pH can be measured in the field
by using pH papers with a range of 3.0 to 9.0. The
rumen fluid pH is normally 6.0 to 7.0 in cattle on a
roughage-based diet and 5.5 to 6.5 in cattle on a
concentrate-based diet. In ruminal acidosis (carbohydrate
engorgement) the pH will be 5.0 or less. In
anorexic cattle, because of the constant production
of saliva which has an alkaline pH and a lack of substrate
for the rumen flora to produce volatile fatty
acids, the pH will be alkaline and usually in the range
7.5 to 8.0. Higher pH values can occur with urea
poisoning.
Sedimentation/flotation
This test is an indirect measure of the activity of
the microflora; it must be performed within a short
time following collection of the sample otherwise
it may not be an accurate measure of their activity
within the rumen. The sample of rumen fluid is
placed in a measuring cylinder. The time is measured
for complete sedimentation and flotation of solid
particles. The finer particles sink and the coarser particles
float supported by gas bubbles of fermentation.
In healthy cattle the normal time for sedimentation
and floatation is 4 to 8 minutes. Inactive microflora
results in rapid sedimentation with little floating
material. Chronically anorexic cattle would give this
result.
Redox potential (methylene blue
reduction time)
This test is a measure of the reduction–oxidation
activity of the ruminal microflora and reflects anaerobic
fermentation by rumen bacteria. It must be
performed within a short time following collection of
the sample to produce an accurate result. One ml of
0.03% methylene blue is mixed with 20 ml of rumen
fluid and the colour compared with a control of
rumen fluid only. The time taken to decolourise the
methylene blue is measured. Rumen fluid from
healthy cattle on a concentrate and hay diet will de-
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