The term ketosis is used to refer to a spectrum of conditions associated with low blood sugar and intense fat mobilisation resulting from reduced food intake.
In conditions of persistent low blood sugar the liver attempts to produce sugar from fat. This process involves production of ketones, which in turn have the potential to result in suppression of appetite depending on the levels produced. The result may be persistent inappetence, inanition and death.
The trigger, persistent low blood sugar, is brought about by feed deprivation, inadequate energy in feed, or inappetence caused by stress or concurrent disease such as displaced abomasum, metritis or lameness.
Any class of animal in any physiological state may be affected. Animals that are older, fatter, pregnant or lactating, are at higher risk. Ewes and does that are pregnant with multiple foetuses are t higher risk. In heavily pregnant animals the disease is usually irreversible and fatal, while lactating animals may self-cure by reducing milk production. Some animals may become persistently inappetent and die from inanition. Depletion of rumen flora may be a complication in later stages in some animals and this may explain some treatment failures.
There are numerous potential stressors during the export process that may predispose animals to ketosis including mixing of cattle, introduction to unfamiliar environments, periods of feed or water deprivation during transport and handling, and dietary changes from farm to assembly depot to ship. Older, well-conditioned cattle entering the live export process that become shy feeders at sea and at destination, may be suffering from ketosis.
Inappetence, lethargy, weight loss and reduced abdominal size are often present. Pen inspection will detect sharp transverse processes, hollowing and woody appearance of skin (from loss of skin fat).
A strong reaction to ketones in urine or milk on a dipstick test strip is diagnostic. Ketosis causes the breath to smell sickly sweet. Incessant chewing and licking and sometimes other nervous signs occur in lactating cattle with ketosis. A chilled serum sample may also be tested for beta hydroxybutyrate (one of the ketone bodies produced from fat mobilization in response to low blood sugar) levels.
Differential diagnoses include those causing inappetence and weight loss, such as displaced abomasum and chronic inflammatory conditions such as liver abscess or low grade pneumonia. Hypocalcaemia is a differential for pregnant and lactating animals.
The necropsy of animals that have not eaten for several days and where fat catabolism is occurring, may reveal livers that are enlarged, pale, yellow or orange, and friable. The kidneys may be similarly affected. The rumen and intestines may be shrunken and fat deposits (especially around the kidneys and heart), may appear jelly-like (serous atrophy). A smaller than normal liver and gall bladder may be present in animals suffering long term reduced food intake.
Ketosis can be very difficult to reverse in pregnant and older, fat, non-pregnant cattle. Early detection and treatment is essential to avoid death or protracted recovery.
Isolate suspected cases, feed good quality hay to stimulate appetite and provide energy, and treat concurrent diseases.
Drench with propylene glycol or glycerol daily for 3 days. Follow the manufacturer's dosage recommendations and avoid overdosing.
Administer calcium borogluconate under the skin - in the feedlot industry this is regarded as essential to reverse the ketosis and stimulate appetite.
Glucocorticosteroids such as dexamethasone are effective in reversing ketosis in lactating cattle. In other classes of cattle, the benefits are uncertain and it may be detrimental, exacerbating ketosis by stimulating breakdown of fat and muscle. Glucocorticosteroids are contraindicated if infectious conditions are present.
Rumen inoculation of >3 L but preferably 8-16 L of rumen fluid from a healthy animal may benefit animals with depleted rumen microflora.
Minimise periods of feed deprivation, rapid diet changes and avoid unpalatable or low energy feeds. Provide feed with adequate but not excess energy to meet physiological demand.
Avoid selecting older, fatter or heavily pregnant cattle for the live export process. Minimise the number and duration of stressors.