Re: Matthew Mackay-Smith weighs in on carbs

[K S Swigart <katswig@deltanet.com>]

In her article, "Carbohydrates, the basis of the Equine Diet" in the May/June 
1998 Issue of _Trail Blazer_ magazine, Dr. Kathleen Crandall, PhD in the opening 
paragraph states:

"Have you ever been worried about too much carbohydrate in your horse's diet? 
Because 75% of all plant matter is comprised of carbohydrates, it is difficult 
for a horse to have too much carbohydrate.  Not only are the grains you are 
feeding mostly carbohydrate, but so are pasture, hay and any sort of 
roughage...Why are carbohydrates important to the horse?  The bottom line is 
they provide energy, whether that energy is use immediately or store for future 
use.  The horse evolve with a high carbohydrate diet an its digestive tract is 
very well suited to carbohydrate breakdown and utilization."

So to say, as Matthew Mackay Smith (MMS) does:

" The endurance horse has no more inimical nutrient than carbohydrate. It is his 
food of 
last resort. Why? Carbohydrates activate all the inappropriate metabolic 
pathways and set 
the horse up for so many disastrous consequences which are ruinous to 
performance--colic, tying up, poor pulse recoveries, exhaustion, to name a few."

If Kathleen Crandall is correct (which considering MMS is touting her new 
endurance horse feed later in his post), then "carbohydrates are an inimical 
nutrient" to endurance horses would surely make endurance horses unlike all 
their other equine counterparts.

However, it is interesting to note that she also says in the first paragraphs of 
her article, "...Although they all contain carbohydrates, not all carbohydrates 
are created equal.  Generally there is a delicate balance of different types of 
carbohydrates in the diet of the horse.  Problems occur when too much of one 
type of carbohydrate is fed or not enough of another...Even though both feed an 
forage are mostly carbohydrate, they are digested very differently in the horse 
in order to provide the energy needed."

It may be that MMS meant that "grain" is inimical to endurance horses rather 
than carbohydrates are.  If he really believes that carbohydrates are bad for 
endurance horses, then to quote him, he is "absolutely off the mark."

Carbohydrates in their various forms are the staple of any horses diet (this, 
actually is true of most animals); and determining the best way to provide these 
to our horses is what all the debate was about (grain vs. forage).

Kathleen Crandall's article goes on to describe the various forms that 
carbohydrates take and the various ways that horses digest them and make them 
available for use, and I can heartily recommend it to anybody who has been 
interested in the recent "great feed debate."  It provides many insights into 
understanding how horses digest food, and what may be the best balance of the 
different types of carbohydrates for optimal energy production and overall horse 
health.

It is not a terribly technical article and is therefore fairly easy to 
understand without a PhD in organic chemistry, but does (I think) a good job of 
shedding light on the vagaries of feeding carbohydrates.

MMS goes on to say:

"Fat is the endurance horsešs friend. Soluble fiber is the endurance horsešs 
friend. The 
high fat and fiber feed (EnduroEvent--Ed.) recently developed by David Kronfeld, 
BVSc, MVSc, PhD, and Kathleen Crandell, PhD, and now offered commercially by 
Pennfields (and soon others, we hope) is the answer to the endurance rideršs 
prayer."

This may be so, but I am willing to bet that this new feed (EnduroEvent) is also 
PACKED with carbohydrates (the fact that it contains fiber means that it 
contains some carbos).

However, I am disinclined to jump on the bandwagon and state the any "recently 
developed" feed IS the answer to the endurance rider's prayer.  Until it has 
been tested and proven in the field (i.e. on endurance horses) I would only be 
willing to say that it MAY be.

As to feeding fat to endurance horses, this is definitely a departure and an 
"innovation," one cannot make the assertion that horses evolved on a diet of 
fats.  The horse's diet for millennia contained virtually NO fat.  And I have 
yet to see it conclusively demonstrated that "fat is the endurance horse's 
friend."  (I don't think it has been demonstrated that it isn't, and I think 
that there is some evidence that it might be...if for no other reason than fat 
is high in calories, and endurance horses need lots of calories.)

I do recall, however, reading one study (don't ask me to quote it, I don't 
remember...so you must take that with the grain of salt that is its due) that 
horses on high fat diets had slower neural responses.  If this is true (and I am 
not saying it is), then it is fat (despite its high calorie content) that may be 
inimical to endurance horses.  If this is true, the kinds of problems we can 
expect to see from feeding fat are:  stone bruises, pulled suspensories, twisted 
ankles" and all the other assorted lamenesses that come from taking a "bad 
step."  And therefore may not be attributed to the feed at all.

Additionally, the feeding of fat is so new in equine nutrition, that there just 
isn't enough data to determine whether and to what extent it may cause problems 
by  "activate(ing) all the inappropriate metabolic pathways and set(ting) 
the horse up for so many disastrous consequences which are ruinous to 
performance--colic, tying up, poor pulse recoveries, exhaustion, to name a few."

I do not make these points to state that "carbohydrates are good, fat is bad" 
for endurance horses, but rather to demonstrate that "carbohydrates are bad, fat 
is good" is no more accurate.  And I must confess to being somewhat disappointed 
to have heard it coming from Matthew Mackay-Smith.

The jury is still out on the best way to feed endurance horses, and the issue 
becomes even more clouded when one takes into account that endurance horses vary 
all over the map, and the best way to feed one horse may not be the best way to 
feed another.  Some horses have the ability to process grains very well, some do 
not, some have the ability to process hay well, some do not.  

The wise thing to do (IMO) is to make note of what everybody else is doing (and 
has done) and this includes watching what they are doing on the race track 
(since race track people are also faced with having to provide more calories to 
their horses than can be provided by letting them graze for 18 hrs a day--and 
endurance horse cannot graze for 18 hrs a day AT an endurance ride, no matter 
how it is fed at home).

Of further concern, which has only marginally been touched on is "palatability."  
The best mix of feed in the world for your horse isn't going to do him ANY good, 
if he won't eat it.  As a general rule, no matter what the nutritional content 
of the feed, food that the horse will eat is better than food that it won't :).

kat
Orange County, Calif.

p.s.  There is also and interesting article in _The Horse_ (July 1998) on
"the latest" in feeding horses.  It had some recommendations for feeding
young horses that I am NOT going to follow, but the article was
interesting just the same.  Not the least of reasons being that the
studies they used to determine the best way to feed young horses was based
on the premise that optimal growth was the goal.  This is not MY objective
when feeding youngsters.  Realize that many of the studies done on the
"best way to feed horses" have very different goals than we have as
endurance riders, and to date, there haven't been any real studies (otheer
than the "one rat" variety that each of us does at home and at endurance
rides) with these goals in mind (recognizing, of course, that not even all
endurance riders have the same goals in feeding their horses).