Page 944 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Endocrine system 919

VetBooks.ir factors include stress, malnutrition and intestinal observance of lipaemic plasma. Liver enzymes and
function tests should be measured in cases of hyper-
parasitism.
Negative energy balance results in activation of
hormone-sensitive lipase and mobilisation of glycerol, lipaemia. Additional testing to identify possible
inciting causes should be undertaken.
free fatty acids (FFAs), and non-esterified fatty acids
(NEFAs) from adipose tissue. These nutrients travel Management
in the blood to the liver, where they can be converted The two primary goals of treatment are (1) to identify
to glucose by gluconeogenesis or oxidised to acetyl- and treat the inciting cause of the negative energy
CoA. Fatty acids can also be converted to ketones, balance or the underlying disease, and (2) to improve
and in many species, ketosis is an important result of the energy balance. Depending on the severity of the
fat mobilisation. This does not occur to a significant hyperlipaemia, improving the energy balance may
degree in horses because they have efficient ketone be as simple as offering palatable feeds to encour-
transport into the mitochondria, where they can be age eating. Administration of NSAIDs may improve
processed into energy via the TCA cycle. The large appetite in horses with high fevers or who are in pain.
volume of FFAs that are mobilised from the adipose Provision of a higher energy diet or force-feeding via
tissue are both re-esterified to triglycerides and very nasogastric tube may also be effective in mild cases.
low-density phospholipids and accumulate in the hepa- Preparations that can be administered by nasogas-
tocytes, which leads to fatty liver. The peripheral tis- tric tube include solutions of glucose (or dextrose)
sues cannot use the phospholipids as quickly as the liver and electrolytes, gruels made from pelleted feeds or
produces them, leading to increased blood concentra- commercially available enteral solutions. Improperly
tions of triglycerides and grossly lipaemic serum. balanced home-made solutions containing glucose
and electrolytes may exacerbate metabolic acidosis
Clinical presentation or result in hyperglycaemia. Commercially available
Clinical signs include anorexia, depression and weak- enteral solutions are convenient but may be cost pro-
ness, progressing to muscle fasciculations, ataxia, hibitive except in smaller equids. Gruels made from
head pressing, circling, recumbency and convulsions complete pelleted feeds have the advantage that they
or coma. Ventral oedema may be present. Diarrhoea are nutritionally complete and relatively inexpensive,
may accompany the syndrome, either as an inciting but they require coadministration of a large volume
cause of the negative energy balance or secondary to of water to keep the gruel from clogging the tube.
anorexia. Parasitism may contribute to poor appetite This large volume makes it necessary to administer
and compete for nutrients. multiple meals (usually a minimum of six) through-
out the day, in order to satisfy dietary requirements
Differential diagnosis without overloading the stomach. It is usually neces-
The primary clinical signs of anorexia, depression sary to start with a smaller amount of feed (e.g. 50%)
and weakness are non-specific and can be caused on the first day and gradually increase the amount
by many diseases. Often, hyperlipaemia occurs sec- given per feeding over a few days until either 100%
ondary to another disease process and the initial of the required diet is reached or the horse begins
clinical signs of hyperlipidaemia are either missed eating voluntarily.
or ascribed to the original problem. Primary dif- Moderate cases of hyperlipaemia may require i/v
ferentials for anorexia should include fever or GI infusion of glucose (5 or 10%) and/or force-feeding
problems including, but not limited to, colic, gastric by nasogastric tube. Concurrent administration of
ulcers and colitis. Differential diagnoses for the diar- a balanced electrolyte solution is required to pro-
rhoea include the various causes of colitis. vide maintenance fluid requirements and account
for any ongoing losses (i.e. diarrhoea). Fluid ther-
Diagnosis apy is particularly important in azotaemic ani-
Diagnosis is made by measurement of elevated tri- mals. Frequent monitoring of blood glucose levels
glycerides (>6.65 mmol/l [500 mg/dl]) in plasma or should be performed to help maintain a steady level.