Insulin Resistance
Posted by: "ladywife" ladywife@comteck.com vickiladywife
Feb 10, 2007

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Debbie,

For years I have carefully avoided using the term "insulin resistance" in
any of my posts to the lists because I didn't want anyone to panic that
their donkeys have a dreaded, incurable disease called insulin resistance,
but now that it has been mentioned, we should talk about it.

Okay, first thing: Insulin resistance is NOT A DISEASE. So everyone take a
deep breath and relax.

Insulin resistance is the metabolic survival mechanism our donkeys inherited
from generations and generations of their ancestors adapting so they could
survive and thrive in harsh environments where there was sparse forage.

Insulin resistance is not a disease, it is their genetic inheritance and the
reason donkeys can not tolerate rich grains, feeds, and forage. Those feed
items are formulated and fortified with packed nutrition for a horse's
much-less efficient digestive system. Now finally after 30+ years
researchers have noticed horses descended from ancestors from the same type
of harsh environments as our donkey's ancestors, can't tolerate that
fortified nutrition feed formulas either, such as Arabs, Morgans, and
Icelandic horses to name a few.

That new awareness is a bonus to donkey owners because now research is being
directed toward creating a more suitable feed for those types of horses and
it will benefit our donkeys too. I can't think of the name of it at the
moment (one of those increasingly frequent memory holes) but there is now a
vitamin and mineral fortified low carb alternative equine packaged feed
being produced that is based on beet pulp and whole oats, very similar to
the donkey diet I have talked about many times on the lists.

Globs of fat deposits on the top line of a donkey; developing a fat crest
and pones of blubber on the top of the back, draping over the ribs, and
those poofy fat butts are all indications the donkey's inherited survival
mode is storing fat preparing for times of famine. That is a natural and
normal thing for a donkey to do, it is their body's survival instinct. It
is also unhealthy for them and means our husbandry method has not been
adapted to his dietary needs.

I am going to copy/paste a Fact Sheet by Dr. Jenifer Nadeau, Equine
Extension Specialist, University of Connecticut

http://www.canr.uconn.edu/ansci/ext/insulinresistance.htm

Insulin resistance is a newly recognized problem in horses that may have
been around a long time. You may be wondering what it is all about and how
your horse may/may not be affected. It is probably not as common a problem
as it may seem. This article will discuss insulin resistance including its
causes, effects, diagnosis, treatment and prevention.

What is Insulin Resistance?

Glucose (sugar) normally functions to fuel many metabolic
processes in the body and is the primary energy currency of the body.
Insulin is normally produced in response to elevated blood glucose and is
key to the regulation of blood glucose concentrations and glucose
utilization. Insulin promotes glucose uptake by cells and promotes
formation of glycogen or fat. Insulin resistance is defined as a reduced
sensitivity of the body's cells to insulin's facilitation of glucose uptake.

Basically what happens in insulin resistance is that the cells
become resistant to the glucose uptake action of insulin. Initially, this
just means that more insulin is needed (hyperinsulinemia) to keep blood
glucose concentrations within normal limits after a starchy or high sugar
meal. If it is severe enough even super high insulin concentrations are
ineffective and blood glucose may also be abnormally high. The problem is
that not only does this limit energy availability to the cells but insulin
also has other effects on the body that may be detrimental when it is higher
than normal for prolonged periods of time. Unlike humans, horses rarely go
into the second stage, where the pancreas becomes "exhausted" and no longer
can secrete adequate insulin.

Causes

The exact cause of insulin resistance is still unknown.
However, several possible causes include:

* Diet - In a recent study, horses had increased insulin resistance
when fed high sugar/starch feeds compared to high fiber and fat rations,
especially when they were not obese.
* Obesity - Overweight horses tend to be insulin resistant, as are
"easy keepers" even if they are not obese.
* Age - Old horses (>20 years) seem to be more prone to insulin
resistance, probably secondary to pituitary dysfunction (Cushing's disease)
which is extremely common, especially in mares.
* Breed - Ponies were found to have higher degrees of insulin
resistance than Dutch Warmbloods or Standardbreds. Breeds that are prone to
developing cresty necks and obesity, such as Morgans and some lines of
Arabians, Quarterhorses, and Thoroughbreds may be more likely to develop the
problem, although a study conducted at the University of Connecticut
comparing exercising Morgans and exercising Thoroughbreds did not find a
difference between breeds in insulin resistance.
* Laminitis - Horses with a family history of laminitis and horses
that develop laminitis without an obvious cause (grain overload, sudden
access to lush, green grass) may be insulin resistant.

Effects of Insulin Resistance

Insulin resistance may result in:

* Loss of weight

* Loss of muscle

* Lack of stamina

* A condition similar to human Type II diabetes

* Laminitis

Diagnosis

Your veterinarian will be able to diagnose insulin resistance.
A single blood sample drawn within 60 to 90 minutes of eating a meal of
grain is a quick screening test for hyperinsulinemia. If the results are
abnormal the veterinarian should perform a more reliable test by
administering a glucose challenge orally or intravenously and measuring the
glucose/insulin response over the course of two or three hours. This is not
usually practical in the field and the horse may need to be referred to a
clinic to get such tests done.

Treatment

Treatment may consist of the following:

* Weight loss through diet and exercise if the animal is obese

* Addition of a minimum of 30 min of exercise

* Limiting carbohydrate intake through elimination of grain and high
sugar feeds

* Soaking hay if it is know to contain high amounts of sugars (> 10
to 12% soluble sugars)

* Feeding warm season grasses, such as Bermuda grass, or feeding beet
pulp that does not have added molasses

* Cutting down on free choice intake of grass if the horse has a
history of founder and is obese

Prevention

Preventative measures to reduce insulin resistance are:

* Feed primarily grass or legume mix hay or pasture. If the horse
tends toward obesity, limit access to the forages and feed no grain at all!

* If concentrates are needed to maintain body condition, feed
products formulated to have a low glycemic index. For example, oats are
commonly used as the standard with an index of 100. Plain beet pulp has the
lowest index in most studies and barley has the lowest index of the commonly
fed grains.

* Test pastures and dry forages for amounts of sugars present.

* Soak high sugar hay in hot water for 30 min or cold water for 60
min

* Restrict grazing time but only if the horse has a pre-existing case
of laminitis and grass is lush

* Add fat and fiber to the diet at 6-10% for fat and at least 12% for
fiber.

Insulin resistance can be a serious problem, but actual
statistics on insulin resistance are currently unavailable. An accurate
medical diagnosis by a veterinarian is extremely important. As with most
equine health concerns, prevention is better than treatment. By paying
careful attention to diet and condition of your horse, you may be able to
prevent insulin resistance from becoming a problem in your horse.

Sources:

1. A.J. Forhed and H. Dobson. 1997. Plasma glucose and cortisol responses
to exogenous insulin in fasted donkeys. Research in Veterinary Science 62:
265-269.

2. R.H. Hoffman, R.C. Boston, D. Stefanovski, D.S. Kronfeld, and P.A.
Harris. 2003. Obesity and diet affect glucose dynamics and insulin
sensitivity in Thoroughbred geldings. Journal of Animal Science 81:
2333-2342.

3. J. Meszoly. April 2004. Danger in the grass: how you can protect your
horse. The Horse p. 61-71.

4. S. Ralston. October 2004. Equine metabolic syndrome. The Horse p.30.

5. A. Rodiek. June 2003. Sugar levels in horse diets. Horse Journal p. 16.

6. L. Sellnow. April 2004. Obesity and Cushing's disease. The Horse
p.83-90.

7. S. Wenholz. April 2005. A closer look at insulin. The Horse p. 91-98.

Source: http://pets.groups.yahoo.com/group/DonkeyMuleInfo/message/34928

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