Re: gut sounds

Susan Evans Garlinghouse (suendavid@worldnet.att.net)
Wed, 19 Nov 1997 21:51:06 -0800

DreamWeaver wrote:
>
> Hi Susan:
>
> Thanks for all the great information, and the sense of humor. I have
> another question (as usual...)...
>
> How long does it normally take a horse to process their food? Say my horse
> is eating hay right now...how long till...ah...it comes out the other end?
> I know that time will vary greatly depending on many different factors.

Hi, sorry it took me so long to answer...on occasion, I do actually show
up to class, and sometimes even midterms, just to keep the faculty on
their toes and wondering what the hell I'm up to this week <g>.

To answer your question, the average time of passage from one end to the
other is around 65-75 hours, more or less. Under normal circumstances,
the rate of passage is fairly constant, although there are factors that
can speed it up or slow it down...stress, disease, unusual/toxic feeds
that upset or irritate the gut can speed things up and cause diarrhea
(which is just poop that got jettisoned before the excess water had a
chance to get reabsorbed, which is why critters with diarrhea can get
dehydrated quickly), or things can be slowed down by a lack of gut
motility, whether that means a lack of adequate blood flow, obstruction
or whatever.

Normally, though, the rate of peristalsis (fancy-shmancy word for the
waves that move food through the GI tract) is pretty steady. This is
why you'll sometimes see undigested grain in horse's poop---the conveyor
belt just moves food past the microflora, and if they just can't quite
finish the job before the food has gone it's merry way, then it just
gets dumped without having been totally digested yet.

Wendy posted something about grain going through faster than hay, but I
think what she meant (and she would be right) was that some of the
nutrients in different feeds are ABSORBED at different rates---that is,
blood glucose levels from corn would rise much sooner than would glucose
from a less-soluble carbohydrate source, such as beet pulp. Energy
derived from hays would be absorbed even later than that, depending on
the fiber content and composition. Different nutrients, such as
carbohydrates, amino acids, VFAs, etc are absorbed at different places
along the GI tract.

The reason why you get an almost immediate response in gut motility when
a horse starts to eat is not necessarily that the food has so quickly
reached the hindgut (which is a long ways from the mouth), it's that
there are alot of hormones involved that get "turned on" as soon as the
horse sees food coming his way, and even more as soon as food hits the
stomach. There are a whole slew of different hormones, all of which are
triggered by different things going on during and after a meal---some
cause the release of specific digestive juices, others control how fast
or slow food leaves the stomach, others control the blood flow to the GI
tract. There are quite a few that control the motility of the various
parts of the gut, and when you feed a horse, what you're really doing is
turning on all the machinery in preparation for food that's on the way
but not quite there yet. In the case of a too-quiet gut and a
borderline colicky horse, you really don't need hay actually in the gut
to get the gut moving again---you need it to be on the way (as in in the
mouth and hitting the tummy), and the machinery will automatically get
going again in anticipation. Voila, moving gut.

>
> I'm just curious to find out how long on average it should take a horses
> gut sounds to pick up if they are diminished and the horse is currently
> eating. For instance, I know that if I stop at about 42 miles into a 50
> mile ride and let my horse eat for 15 minutes, that by the time we finish
> and vet thru his gut sounds will be really good.
>

> Does exercising a horse throw off their normal rate of digestion? It seems
> that during a ride they seem to stay pretty 'regular'.

There are some numbers around that estimate that maximum blood flow to
the gut and maximum digestive efficiency occur at around a brisk walk to
slow trot---one of the reasons why a vet will tell you to walk a colicky
horse, aside from preventing him from rolling. Beyond a slow trot, the
relative proportions of where the blood is going shifts away from the
gut and goes to feed the muscles, organs and skin to a greater extent.
At maximum effort, the majority of the cardiac output is going to the
muscles and blood to the gut is minimal---which is why horses being
overridden tend to start getting progressively quieter gut sounds.

Although at a normal endurance trot, there isn't quite as much blood
flow going to the gut as there would be at a walk, there is still plenty
of blood to maintain good gut motility, as long as you don't start
pushing your horse beyond his abilities, and as long as you try to keep
some food in the system as much as possible to keep the endocrine
systems active and happy. If gut sounds start to diminish during a
ride, that's a strong hint to back off a little and get some hay into
your horse.

Seeya,

Susan Garlinghouse