PATHOLOGY - Equine Obesity

Question 1

What is the ideal body condition score for a horse based on the five point scale?

Answer 1

Based on the five point scale, a body condition of 3 is ideal

Question 2

Describe a body condition score of 3 in a horse based on the five point scale

Answer 2

You can feel but not see the ribs
Straight neck profile (no neck crest)
Rounded rump without a gutturing effect

Question 3

What are the benefits of the cresty neck scoring system in horses?

Answer 3

The cresty neck scoring system is more predictive of insulin dysregulation than body condition scoring and thus can be relevant to the diagnosis of equine metabolic syndrome (EMS), and this system can be easily used by owners

Question 4

What are some of the more common presenting clinical signs of obesity in horses?

Answer 4

Recurrent laminitis
Dyspnoea
Exercise intolerance
Poor performance

Question 5

What is one of the first things you should determine when presented with an obese horse?

Answer 5

When presented with an obese horse, you should determine if the obesity is uniform or if there are abnormal fat deposits

Question 6

Which equids are more prone to obesity?

Answer 6

Ponies
Donkeys
Minature equine breeds

Question 7

How do you manage obesity in horses?

Answer 7

Dietary management
Exercise
Manage any complications of obesity

Question 8

Which dietary modifications are required for managing obesity in horses?

Answer 8

Low calorie roughage
Soaked roughage
Limit roughage intake
Remove concentrates from the diet
Grazing muzzles if on pasture
Grazing at night if on pasture

Question 9

What is the ideal roughage to use for managing obesity in horses?

Answer 9

Hay with less than 10% non-structural carbohydrates

Question 10

How much roughage/forage should be fed to a horse that needs to lose weight?

Answer 10

1.25 - 1.5% of body weight in dry matter

Question 11

Why is it important to soak roughage when managing obesity in horses?

Answer 11

Roughage should be soaked to remove soluble sugars

Question 12

What do you need to supplement if feeding horses soaked hay to manage obesity?

Answer 12

If you are feeding soaked hay to manage obesity, make sure to supplement them with proteins and water soluble vitamins

Question 13

What are the benefits of turning out horses at night when trying to manage obesity?

Answer 13

It is beneficial to turn out horses at night when managing obesity as this is when fructan (a non-structural carbohydrate) levels are low due to the lack of photosynthesis at this time

Question 14

What are the main diseases associated with obesity in horses?

Answer 14

Laminitis
Equine metabolic syndrome (EMS)
Hyperlipaemia
Infertility
Mesenteric pedunculated lipoma (causes small intestinal strangulation and acute colic)

Question 15

Which diseases should be investigated for in horses with laminitis?

Answer 15

Equine metabolic syndrome (EMS)
Equine pars intermedia dysfunction (PPID)

Question 16

Describe the basic pathogenesis of equine metabolic syndrome (EMS)

Answer 16

Insulin resistance is a hallmark of equine metabolic syndrome (EMS). Insulin resistance in horses can occur due to obesity, as the adipose tissue releases inflammatory cytokines and acute phase proteins which lead to a chronic low grade inflammatory and physiological stress response (increased cortisol) which contirbute to insulin resistance. To compensate for this, the pancreas produces and secretes more insulin resulting in hyperinsulinaemia, which can progress from post-prandial hyperinsulinaemia to basal hyperinsulinaemia and hyperglycaemia. Hyperinsulinaemia can contribute to many of the complications of EMS including obesity, abnormal fat deposition, and an increased risk of laminitis. Hyperinsulinaemia can comprimise the blood flow to the laminae, cause inflammation and necrosis of the blood vessels and a hypercoagulable state, all of which can cause laminitis. Furthermore, decreased glucose uptake (i.e. due to insulin resistance) can result in increased activation of matrix metalloproteinases (MMPs) which will break down the extracellular matrix (ECM) and basement membrane which forms the junction between the dermal and epidermal laminae, resulting in lamellar separation

Question 17

(T/F) Horses that have previously been obese can still develop equine metabolic syndrome (EMS)

Answer 17

TRUE. Horses that have been previously obese are prone to insulin dysregulation and EMS even if they have lost the weight

Question 18

What is the function of adiponectin?

Answer 18

Adiponectin is a hormone and adipokine which decreases the release of inflammatory cytokines from the adipose tissue and increases glucose uptake. Adiponectin also reduces gluconeogenesis, glycogenolysis and fat breakdown in the liver

Question 19

How can adiponectin be used in the monitoring of equine metabolic syndrome (EMS)?

Answer 19

Adiponectin assays can be used as low adiponectin levels can indicate an increased risk of insulin resistance, insulin dysregulation and the development of equine metabolic syndrome (EMS)

Low adiponectin is caused by genetics and breeding

Question 20

How do you diagnose equine metabolic syndrome (EMS)?

Answer 20

Combined insulin-glucose tolerance test

Question 21

How do you carry out a combined insulin-glucose tolerance test?

Answer 21

1. Fast the patient for 12 hours
2. Take a blood sample for baseline serum glucose
3. Administer 0.3ml/kg of 50% IV glucose and 0.1iu/kg of IV soluble insulin
4. Take sequential blood samples to assess serum glucose levels, and a blood sample at 45 minutes to measure endogenous insulin
5. In patients with insulin resistance, blood glucose levels will take longer to return to baseline. Furthermore, endogenous insulin will be higher in response to glucose challenge, however the blood glucose levels will still take longer to return to baseline

Focus more on interpretation rather than the doses and times

Question 22

How do you treat equine metabolic syndrome (EMS)?

Answer 22

Weight loss
Exercise (once the laminitis is controlled)
Anti-hyperglycaemic agents

Question 23

Which anti-hyperglycaemic agents can be used in the treatment of equine metabolic syndrome (EMS)?

Answer 23

Metformin
SGLT 2 inhibitors

Question 24

What is the mechanism of action of metformin?

Answer 24

Metformin increases the sensitivity of the liver to insulin to reduce gluconeogenesis and improves the peripheral uptake of glucose

Question 25

What are the limitations of metformin in horses?

Answer 25

Metformin only has a short-lived response in horses *(only effective 2 - 3 weeks)*

Question 26

What are the limitations of SGLT 2 inhibitors in horses?

Answer 26

SGLT 2 inhibitors can cause inappetence and anorexia in horses which will result in excessive mobilisation of fat stores which trigger hyperlipaemia. It can be beneficial to start horses on a low dose and build up to a maintenance dose with close monitoring

Question 27

What should you monitor in horses on SGLT2 inhibitors?

Answer 27

Serum triglyceride levels Liver enzymes

Question 28

What is hyperlipaemia?

Answer 28

Hyperlipaemia is particularly seen in obese horses which develop a negative energy balance *(maybe due to anorexia)* and mobilise excessive fat stores resulting in increased triglyceride synthesis by the liver, hepatic lipidosis and insulin resistance. This can progress to metabolic acidosis

Question 29

What are the risk factors for hyperlipaemia?

Answer 29

Breed *(donkeys and native ponies)* Obesity Pregnancy Inappetence/anorexia Underlying disease Stress Equine metabolic syndrome (EMS) Equine pars intermedia disorder (PPID)

Question 30

What are the clinical signs of hyperlipaemia?

Answer 30

The initial clinical signs can be very subtle but if an obese donkey/pony starts to seem unwell you should suspect hyperlipaemia and investigate as this condition and clinical signs progress very rapidly

Question 31

What are the early clinical signs of hyperlipaemia?

Answer 31

Lethargy Inappetence Adipsia *(not drinking)* Weakness Reduced faecal output Mucus coated, thickened faeces

Question 32

What are the progressive clinical signs of hyperlipaemia?

Answer 32

Reluctance to move Muscle fasciculations Intermittent abdominal pain Diarrhoea CNS dysfunction

Question 33

What are the late clinical signs of hyperlipaemia?

Answer 33

Recumbency Seizure Nystagmus Altered mentation Abortion

Question 34

What are the biochemistry changes expected in a horse with hyperlipaemia?

Answer 34

Hypertriglyceridaemia Hypercholesterolaemia Hyper-/Normo-/Hypoglycaemia Increased liver enzymes Increased bilirubin *(hepatic dysfunction)* Increased ammonia *(hepatic dysfunction)* Azotaemia Metabolic acidosis *(on venous blood gas analysis)*

Question 35

How does the plasma appear in patients with hyperlipaemia?

Answer 35

The plasma will appear opaque

Question 36

How do you treat hyperlipaemia in horses?

Answer 36

Nutritional support IV fluid therapy Diuretics *(to correct acidosis)* Insulin injections Supportive care

Question 37

Why is nutritional support so important in the management of hyperlipaemia?

Answer 37

Nutritional support reverses the negative energy balance, increasing blood glucose which increases insulin release and consequently reduced lipolysis