Digestion of grain/carbos

[RALSTON@AESOP.RUTGERS.EDU]

Ti, you really goofed this time when you Wrote:

>In the horse, carbohydrates are 
>digested in the stomach. If too large a carb
>load is fed, then some of it will move on into the intestine, often resulting
>in colic and other problems. We must also take care to know precisely what we
>are talking about before putting keyboard in gear.

Let me briefly explain digestion in the horse (based on sound scientific
data published over the past 30 years):

Feeds are ingested, chewed, mixed with saliva and swallowed, passing down
the esophagus to the stomach. There is some secretion of acid and perhaps 
pepsin
in the equine stomach, and if the feed is highly fermentable  (read grain
and sugars) and gastric emptying delayed (by stress, exhaustion or high fat
intake) some fermentation can take place in the stomach. HOWEVER there is
NO absorption of nutrients from the gastric mucosa and under normal
circumstances, minimal fermentation-the build up of gases from abnormal
stomach fermentation IN THE STOMACH is what causes the colic you were
referring to. The ingesta passes from the stomach to the small intestine

where the simple carbohydrates, proteins and fats are subjected to enzymatic
digestion and their component parts (simple sugars, amino acids, fatty acids)
absorbed. What ever is left goes on down to the cecum and large intestines
where bacterial and protozoal populations ferment both the fibrous and
carbohydrate components into volatile fatty acids which are efficiently
absorbed and readily utilized as energy sources for working muscles.
There are a lot more picky details but I don't have time to go into them.
(Susan?)

Until you have actually seen our endurance horses in action, I suggest you
restrict comments suggesting that just because they are fed differently
from your race horses that they are underfed or not competitive. It only
serves to inflame our warriors out there!

My invitation to attend the rides in NJ stands-I think we could both learn a
lot from each other. If anyone else has nice flat rides (ti says he gets 
vertigo in high places) you might try to get him out to rides closer to
his home!! He has a lot of experience and knowledge, just needs a bit of 
horizon broadening. Thank god we never stop learning....

Sarah Ralston, VMD, PhD, dACVN
and Fling (are we really going to do a second 3 day 100? is that why you
are riding me twice a day and putting all that yucky salty stuff in my feed?)