Page 381 - The Veterinary Laboratory and Field Manual 3rd Edition

350 Susan C. Cork, Willy Schauwers and Roy Halliwell

See the texts in the bibliography at end of yielding dairy cows, twin lamb disease and
this chapter for more details. The five biochemi- ketosis in ewes with multiple lambs. The term
cal tests outlined above are very basic and have ‘metabolic disease’ has also been applied to
largely been superseded by new kit test and other nutrient deficiencies (that is, copper defi-
automated systems. However, simple biochemi- ciency) or functional disturbances (that is, bloat)
cal tests such as these may still be useful in small but usually the term refers to one or more of the
district facilities where reagent supplies can only following conditions.
be sourced locally and equipment is limited.
1 Acidosis/ketosis in ruminants occurs follow-
ing grain overload or due to an imbalance
7.7 Metabolic diseases and of dietary carbohydrates resulting in a lack of
endocrine disorders glucose precursors. Ketosis also develops in
starvation and diabetes.
Metabolic diseases (for example, acidosis, 2 Twin lamb disease in ewes occurs due to an
ketosis, electrolyte or mineral imbalance) and increased demand for glucose and lack of
endocrine disorders (for example, diabetes mel- carbohydrate intake during late pregnancy.
litus, hyper- and hypothyroidism, parathyroid Ketosis develops after liver glucose supplies
disorders, adrenal gland disorders) are often are used up but can be avoided if ewes car-
linked. Tests can be done to diagnose disease in rying twins are fed a low-bulk, high-quality
individual animals or used to monitor the health diet.
status of groups of animals, that is, metabolic 3 Hypocalcaemia (low blood calcium), occurs
profiles. Many tests for endocrine disorders (for due to a total or relative lack of calcium in the
example, adrenal disorders) require repeated diet. It may also occur due to lack of ability
sampling and/or dynamic testing (for example, to mobilize calcium from the bones in early
ACTH stimulation test, dexamethasone suppres- lactation.
sion test) in which an animal is given an injection 4 Hypomagnesaemia (low blood magnesium),
of a specific hormone so that the response can results from an inadequate level of magne-
be measured in the next blood sample taken and sium in the diet. This may occur in cattle
compared with a pre-treatment value. Endocrine grazing young fresh pasture which is low in
disorders will generally only affect an individual magnesium or can be associated with hypo-
animal and it may not be practical to perform the calcaemia in lactation tetany.
required diagnostic tests in a small diagnostic
laboratory. There are a range of texts available on In many cases more than one metabolic condi-
the subject of endocrinology but in most cases tion occurs at the same time in an animal. It is
diagnosis and treatment is complicated and useful to monitor the general metabolic status
would require referral to a specialist. Metabolic of ‘at risk’ animals to establish whether or not
diseases, however, are not uncommon in live- metabolic disease is likely to occur. Good man-
stock and samples may be submitted to district agement, with special attention to matching
and regional laboratories for testing. Metabolic diet to physiological demand, will prevent many
diseases can be common in high genetic merit metabolic diseases in livestock. This topic is well
livestock under heavy production demand and covered in a number of text books on livestock
generally occur due to an imbalance between nutrition (see reference list at the end of the
nutrient intake versus nutrient demand, for chapter) and will not be discussed further here.
example hypocalcaemia or ‘milk fever’ in high

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