Re: Feed Question (Mcals)

["Susan Evans Garlinghouse" <suendavid@worldnet.att.net>]

-----Original Message-----
From: guest@endurance.net <guest@endurance.net>
To: ridecamp@endurance.net <ridecamp@endurance.net>
Date: Tuesday, February 02, 1999 2:48 PM
Subject: Feed Question (Mcals)


>I am feeding my horse Equine Senior and burmudagrass hay right now.
However,
>the feed tag from Equine Senior does not list DE (digestible energy), TDN,
or
>much of anything else energy-related except for a minimum crude fat %.
>
>How would I go about figuring out what this feed's DE amount is based on
only
>crude fat, crude protein, crude fiber, and a slew of minerals and a
vitamin?
>Or, do I need to call Purina?
>
>I figured out that based on crude fat % (listed as a minimum of 4%), the
feed
>only provided 0.36 Mcal per kg. (Based on 9 Mcals/kg of fat).  How do I
account
>for the other sources of energy from this feed, such as carbos, etc.?
>I can't think that a horse could live off of 0.36 Mcal/kg of E.S. per
day?!?


There's a general rule of thumb that relates fiber content to energy content
that's handy for this kind of thing.

If the crude fiber content is:        Then the approximate Mcal DE/kg is:
<4%                                            3.5 - 3.7
6                                                3.3 - 3.5
10                                               2.9 - 3.1
12                                                2.6 - 2.9
19                                                2.4
24                                                2.2
28                                                2.0
30                                                1.5 - 1.7

This accounts for everything except the fat proportion.  If the fat content
is less than 4-5%, don't bother.  For fat content higher than 4% or so, add
in the .36 Mcal per kg that you calculated above and this'll give you a
reasonably close approximation of the total energy content of the feed.

I agree with Tom that you should feed a horse based on maintaining a good
condition score, not strictly according to the numbers, but I also do pay
attention to the numbers.  Some of those commercial mixes especially look
like a concentrate feed but if the fiber content is over 22-24%, then
there's probably not much in there except hay of some sort, and I'm not
going to expect it to provide alot of energy per pound for a hardworking
horse.  Likewise, if the fiber content is less than 10-12% then I know that
the contents are 100% grain and I should feed it accordingly like a grain,
not a forage---in other words, don't feed the whole bag at once and don't
count on it as a significant source of fiber.

Also, the numbers are useful for as a comparison of what your horse is
eating now versus on another feeding program.  For example, if you know your
horse maintains weight and competes well on 20-22 Mcals a day, and you want
to switch to a different feed, it's handy to know how much of the new feed
you're going to have to provide to supply the 22 Mcals, also to help out
deciding if its cost effective and so forth.  So keep right on crunching
those numbers and good for you.  Just use your own eyes and common sense to
calculate how many calories you think your horse needs, don't depend too
heavily on NRC calculations, as they really can vary pretty widely between
individual horses.  Hope the above table helps.

Susan G