Re: rice bran debate

["Duncan Fletcher" <dfletche@gte.net>]

Thank you Dr. Pagan. I have found several quirks with the NRC feed tables. I
would be interested in your comments on the following:
1. Sample sizes are quite small.
2. Standard deviation numbers (even for forages with larger sample sizes) do
not reflect known differences in things like selenium and magnesium
depending on where a hay is grown. Who knows what the reliability is on the
other numbers.
3. The formulas for DE calculation footnoted do not correspond with the
published numbers.
4. The formulas appear to ignore major DE sources. For example, not have a
component for ether extract (fat), but perhaps this is buried in one of the
constants on the assumption that for a particular class of feed this is
constant.
Are there better sources of information. I have used the NRC numbers because
they were the only ones available.

With regard to the original discussion of stabilized rice bran, we are still
left with the potential of poor calcium regulation caused by excessive
calcium intake (assuming Ca balanced rice bran) - probably not a serious
problem with most horses, but a more significant one for endurance horses.
(I should also point out the Natural Glo does not have added Ca, which
depending on forage used can easily cause an inverted Ca/P).

Duncan Fletcher
dfletche@gte.net

>From: Dr. Joe D. Pagan
>Email: pagan@ker.com
>
>Dear Ridecamp subscribers
>
[snip]
>Now for the data:
>A key (and valid) argument made by Susan about choosing an appropriate feed
is its total caloric content.  Susan relied on information published by the
1989 NRC about the energy density of rice bran when she made her case
against rice bran.  I'm afraid that the value used by the NRC is much lower
than is true.  Charlie Thomson suggested that this number was low because
the NRC tested raw rice bran, but the answer is even simpler than that.
Many (maybe most)  energy densities listed in the NRC have not actually been
measured in horses.  Many have been taken from other species (cows and pigs)
and some have been calculated using regression equations.  Anyway, we have
directly measured the digestible energy (DE) content of both 15% fat and 20%
fat rice bran.  Susan cited a value of 2.64 Mcal/kg for rice bran.  This is
the value that the NRC assigns to a 13.6% fat rice bran.  As I'm sure you
know, the higher the fat the higher the DE content and most rice brans have
closer to 20% !
>fat.  The measured DE content of a 15% fat rice bran in our lab was 3.17
Mcal/kg and the DE of EquiJewel (20% fat) was 3.78 Mcal/kg.  This is 143%
higher than the value used by Susan and would rank it only below pure
vegetable oil in her list of common horse feed ingredients.  It is also
interesting to note that 1 lb. of EquiJewel provides the same number of
calories as 1 cup (8 fluid ounces) of corn oil.  Which is easier to feed?
>
>Susan also correctly pointed out that many rice brans have a badly inverted
calcium:phosphorus ratio, but as was already stated on this bulletin board,
we corrected that imbalance in EquiJewel.  Susan also mentioned that the
phosphorus in rice bran was not digestible.  This is actually not the case.
The phosphorus in rice bran (and wheat bran) is very digestible and we have
a lot of data to prove it.  This is because even though a great deal of the
phosphorus occurs as phytate, bran contains a large amount phytase enzyme
which breaks phytin phosphorus down.  Of course, this is not such a good
thing if the ration has more phosphorus than calcium, but when balanced,
rice bran can be a good source of phosphorus for horses.
>
>Susan also suggested that rice bran (or fat in general) should be avoided
in a vet gate meal because it delays gastric emptying.  I agree that gastric
emptying may be delayed (much of the research that makes that argument comes
from my lab), but I don't think that is such a bad thing during an endurance
ride.  We have shown that exercise increases rate of passage through the
digestive tract and this may lead to undigested grain entering the large
intestine.  This could lead to a number of problems including colic and
founder.  We are currently conducting research with Arabs regarding feeding
during a vet gate and  hopefully I will have those results to you this
spring.
>
>I hope that these comments are helpful and keep up those lively discussions
since that's how we all really learn.
>
>Sincerely,
>
>Joe D. Pagan, Ph.D.
>President
>Kentucky Equine Research
>
>