Page 369 - The Veterinary Laboratory and Field Manual 3rd Edition

338 Susan C. Cork, Willy Schauwers and Roy Halliwell

animal, raised levels often imply dehydration. endocrine disorders such as hypothyroidism
Low plasma protein may indicate poor nutri- but can also be elevated after a fatty meal in
tional status and is seen in generalized debility. monogastric species.
Assessment of the relative albumin and globulin
levels can give a better indication of nutritional
and health status of the animal. Albumin levels Enzymes
are low in starvation and/or liver disease and
elevated in dehydration. Globulin levels are ele- A range of enzymes can be measured in blood
vated in some immunological disorders and also samples and are present in increased amounts
in chronic disease. following cell damage. Cells of different tissue
types contain varying levels of different enzymes
such that elevation of certain enzymes implies
bilirubin and bile acids damage to specific tissues, however, the inter-
pretation of enzyme assays must be based on
In cases of severe liver damage or in haemolytic clinical history and examination of the animal as
anaemia the plasma and mucous membranes may a range of variations are possible and may lead to
be yellow in colour; this is often due to elevation misleading conclusions. Creatinine kinase (CK
of the levels of bilirubin in the blood and tissues or CPK) is fairly specific for striated muscle and
(jaundice). Bilirubin is a metabolite of haemo- is used as an indication of the degree of mus-
globin which is usually metabolized in the liver. cle damage, that is, in ‘downer’ cows. Alkaline
Levels rise if the breakdown of blood is too rapid phosphatase (AP) occurs in bone (osteoblasts),
(pre-hepatic jaundice) or in liver disease (post- liver, the intestinal wall and so on. Levels are
hepatic or hepatic jaundice). If it is possible to elevated in biliary stasis and fatty liver syn-
determine whether or not the bilirubin is con- drome especially when associated with diabetes
jugated (that is, has been processed through the and metabolic disorders. Lipase and amylase
liver) or not, this will help distinguish pre-from are present in the pancreas and are elevated in
post-hepatic jaundice. In haemolytic anaemia and pancreatitis and some other acute abdominal
other causes of pre-hepatic jaundice there will conditions. AST (formerly SGOT) and ALT (for-
usually be other clinical signs such as elevated merly SGPT) are associated with both cardiac and
temperature and red urine (haemoglobinuria). skeletal muscle and liver tissue. Gamma glutamyl
In cases of pre-hepatic jaundice, it is helpful to transferase (SGGT) tends to mimic changes in
assess the packed cell volume (PCV) of the animal ALT in some species. If there is elevation of AST/
to check for concurrent anaemia. Biliary obstruc- ALT and bilirubin with low albumin levels this
tion secondary to liver fluke infection, neoplasia would indicate that liver damage had occurred.
and other causes will result in elevated levels of Non-specific elevation in enzyme levels can occur
conjugated bilirubin. Bile acids may also be mea- with a range of abdominal or systemic diseases.
sured in the assessment of jaundice and often give
some indication of the severity of liver damage.
Glucose

cholesterol Slight elevations in blood glucose may occur
after a meal in monogastrics. Marked elevations
Cholesterol levels may be measured to evaluate (hyperglycaemia) are indicative of diabetes mel-
metabolic processes; levels are raised in some litus (sugar diabetes due to pancreatic damage

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