Modern Day Equine Urban Legends

We can all think of at least one old horse care myth that has been debunked but they continue to be generated to this day.  One of the most persistent is that fructan causes pasture associated laminitis, but I’ve discussed that twice and won’t go into it again here.

What I have in mind now is something I keep hearing and reading with increasing frequency – that unlike humans, horses do not produce saliva unless they are eating.

SALIVA

from:  Dressagedifferent.com

If this was the case, when you insert a finger into the horse’s mouth when it is not eating  it would feel bone dry.  It doesn’t.  Horses with choke wouldn’t drool.  Horses engaged with the bit wouldn’t foam.  It’s just common sense that this isn’t true if you just think about it a little bit.

It’s true that the largest salivary gland, the parotid, only secretes when the horse is chewing food but the horse has two other major salivary glands and thousands of individual microscopic clusters of saliva secreting cells lining the oral cavity.  These do secrete constantly to keep the mouth moist and that saliva is swallowed.

The second is also GI related; that ranitidine is the preferred drug for treating hind gut acidosis/ulcers.

Ranitidine (Zantac) binds to acid secreting cells in the stomach to block stomach acid secretion.  It will have no effect in the hind gut for the simple reason that there are no acid secreting cells in the hind gut.

Hind gut acidosis itself is a bit of an urban legend that is being used to promote the sales of a variety of supplements.  The alleged acidosis is also claimed to be responsible for a variety of behavior changes and vices.

Acidosis refers to pH.  A pH of 7 is neutral, below 7 acidosis, above 7 alkalosis.  However, in medical terms, e.g. referring to the blood pH, acidosis is any time the pH is below the range of pH normally found.

The pH of the cecum, the first portion of the hind gut, reflects diet and normally ranges from the low 6’s to the low 7’s. The lining of the intestine has to be able to tolerate a range of pH to allow for variety in the diet, including plant material. Fecal pH is often used as a marker instead but is a poor measure of the cecal pH and is always more acidic. Consider these facts from research:

  • horses on pasture of ryegrass and clover had fecal pH of 6.18 while those on high grain feeding, haylage and minimal hay had higher pH.  No symptoms.
  • feeding 2.17 kg (4.77 lbs) of pelleted barley twice a day reduced the fecal pH to 6.39 from 6.74. No symptoms.
  • horses maintained on pasture and fed up to 6.12 kg of oats/day in two meals had no significant changes in fecal pH.  No symptoms.
  • a pelleted 70% corn and oats diet vs hay produced a lowest cecal pH of 6.12 vs 6.75 for the hay diet. Pellet fed horses spent more time chewing wood but there was little effect of neutralizing cecum pH with sodium bicarbonate and time chewing wood was not correlated with pH.  No other symptoms.
  • Weanlings fed a high sugar/starch supplement had fecal pH 6.94 vs 7.99 for high fat and fiber and diet had no effect on behavior or vices.  Behavior was monitored by cameras.  Note: The pH values are higher than adult because weanlings do not yet have full fermenting capacity in the hind gut.

In contrast, horses that develop laminitis after experimental pure fructan overload have a cecal pH of 4.3.

Unless you are feeding a diet that is greater than 70% grain it is unlikely your horse has a hind gut pH that is low enough to produce any symptoms, let alone need a supplement to correct it.  There are individual differences in tolerance for high sugar/starch intake but an invariable sign will be soft manure.  I’ve seen this many times in racing barns and the fix is to feed smaller meals.  There are no changes in behavior, signs of colic or performance effects.

There are enough things that can go wrong with our horses.  We don’t need to conjure up any more.

Eleanor Kellon, VMD

About Dr. Kellon

Graduate of University of Pennsylvania Veterinary School. Owner of Equine Nutritional Solutions, www.drkellon.com, industry and private nutritional consultations, online nutritional courses. Staff Veterinary Expert at Uckele Health and Nutrition.
This entry was posted in Equine Nutrition and tagged , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s