Page 943 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

918 CHAPTER 6

VetBooks.ir Table 6.11 Protocol for 2-step insulin response test

1 Collect baseline blood sample for glucose concentration (no fast and access to hay)
2 Administer regular insulin (0.1 mIU/kg i/v)
3 Collect a blood sample for glucose concentration 30 minutes later
Blood glucose concentration will be increased by >50% in normal horses and smaller or delayed decreases are observed in
horses with equine metabolic syndrome
4 Monitor for signs of hypoglycaemia for 60 minutes, and/or inject 50% dextrose i/v, or provide a high-carbohydrate meal after
collection of the second sample

Management Although weight loss can be managed over time,
There is no rapid cure for EMS. Treatment rec- laminitis is still a very debilitating disease and often
ommendations focus on reducing exposure to a cause of euthanasia. Early detection of EMS before
non-structural carbohydrates and increasing exer- the first episode of laminitis is therefore crucial in
cise, which can be difficult to achieve in laminitic improving the prognosis. Cases of insulin dysregula-
animals. Ideally, horses would be fed 1.5% of their tion in lean horses can be challenging for clinicians
body weight with a hay low in non-structural carbo- to deal with.
hydrates (<12% non-structural carbohydrate by dry
weight). Hay can be soaked (30 minutes in hot water, HYPERLIPAEMIA AND HYPERLIPIDAEMIA
1 hour in cold water) to reduce its non- structural
carbohydrate content. Mineral supplementation Definition/overview
may be required in such cases as minerals and other Hyperlipaemia is a metabolic condition in which
nutrients leach out of the soaked hay alongside excessive fatty acids in the blood cause the serum to
the carbohydrates. The implementation of severe look milky. Hyperlipaemia is the term used when
dietary restrictions in overweight horses can lead serum triglycerides exceed 6.65 mmol/l (500 mg/dl).
to the development of hyperlipaemia and prolonged Hyperlipidaemia refers to a milder increase in serum
periods of fasting (over 6 hours) will lead to insu- triglycerides that is not evident visually. Hyperlipaemia
lin resistance. Exercise should also be encouraged as occurs most commonly in ponies, donkeys and minia-
much as possible within the limits of the episodes ture horses and is rare in other breeds.
of active laminitis. Proper foot care is of paramount
importance and working closely with a good farrier Aetiology/pathophysiology
will improve the prognosis of the horse. Hyperlipaemia occurs when more fatty acids are
Medical treatments with levothyroxine and met- mobilised from adipose tissue and exported from
formin can be used in some cases. Levothyroxine the liver than the peripheral tissues can effectively
is a thyroid hormone supplement that has an indi- utilise for energy production. The condition can
rect effect by increasing metabolic rate, potentiat- be primary in certain equids (e.g. ponies, don-
ing weight loss and fat metabolism. Metformin keys and miniature horses), but is more commonly
may increase insulin sensitivity and decrease post- seen secondary to a disorder that incites a negative
prandial hyperinsulinaemia. It seems, however, that energy balance. The problem is more common in
metformin may be beneficial in only a few cases and overweight individuals or in mares that are in late
therefore dietary and management changes are the pregnancy or lactating. Azotaemia contributes to
main current treatments for EMS. the disease by inhibiting uptake of triglycerides by
peripheral tissues, possibly by inhibiting lipopro-
Prognosis tein lipase. Horses that are insulin resistant may be
The prognosis for EMS largely depends on the at greater risk of developing hyperlipaemia during
severity and frequency of the episodes of laminitis. periods of anorexia or feed restriction. Other risk