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[RC] What the Abstracts Say...and Don't Say (was: Beet Pulp) Part 2 - katswig@xxxxxxxxxxxxx

continued from part 1

The THIRD abstract (I'll discuss the second one after):

The 6 week experiment was performed on growing Wistar
male rats. In the third and the sixth weeks digestibility
trials were performed. The following high fibre preparations
were supplemented to the control diet (C): high methoxylated
citrus pectin (Cr); apple pomace (A), potato fiber "Povex" (P)
and sugar beet pulp (B). Fibre supplementation, except Cr, 
significantly increased Ca, Mg, Fe, Mn, Zn, Cu excretion in
faeces and decreased their apparent absorption in both trials.
Significant correlations (P < or = 0.001) were found between
crude, insoluble and total fibre intake and mineral excretion
and apparent absorption. Apparent absorption of minerals increased
from the third to the sixth week in group C and in group Cr,
except Fe, while it decreased in groups P and B or showed tendency
to decrease. In the sixth week the following differences
(P < or = 0.05) in apparent absorption were observed between
diets, in descending order: [equation: see text]      

What it says they did:

They performed the experiment on young (3 and 6 weeks old) rats.
They ADDED (not replaced) an assortment of different fiber sources to
different rat's diets, while keeping some on no fiber supplementation for
control purposes.

What it doesn't say:

It doesn't say what the control diet was, so we don't know what else these
rats were eating.  In fact, it MAY be (since I don't know enough about the
developmental stages of Wistar rats) that the control diet is mother's milk
and that these rats had not yet even been weaned (in which case if they
were nursing it would be difficult to tell to what extent the
supplementation had on the consumption of milk).  This may be mentioned in
the entire paper, or it may be obvious to scientists who regularly do
experiments on Wistar rats what is a normal diet for 3 week old rats (and
so isn't mentioned in the paper at all); however, it also doesn't say that
the control diet is what these rats would normally eat.

What is says they observed:
Feeding young rats fiber (except citrus pectin) increases the amount of
Calcium, Magnesium, Iron, Manganese, Zinc, and Copper in their feces and so
would appear to reduce their absorption.

Rats on the control diet (i.e. no fiber supplementation) and on the citrus
pectin supplement, appeared to absorb minerals better (less fecal
excretion??) as the study progressed (as the rats matured???) with some
exceptions about Iron.

Rats on the beet pulp or pototo fiber supplements appeared to absorb  less
of these minerals as the study progressed.

Differences in mineral absorption were noticed in the different fiber
supplementation diets.

What it doesn't say:
It doesn't say anything about mineral excretion in the urine.

While it tells you that differences were noticed, it also tells you to read
the text of the paper to find out what those differences actually are.

One of the things that looking at these two combined tells me:

Since supplementing the diet of immature rats with beet pulp appears to
decrease absorption of magnesium in the second study but replacing a part
of the diet with beet pulp in mature horses does not have this observable
effect on absorption of magnesium in horses, the study about the effect of
fiber supplementation on mineral absorption in immature rats is unreliable
for telling me about the effect of adding beet pulp to my adult horse's
diet. Since it is well documented that the digestive tracts of horses and
rats vary greatly with respect to the mechanism they use for digesting
fiber, it is not unreasonable to assume that the effects of feeding fiber
to horses and feeding fiber to rats will differ as well.

The rat study may raise questions in my mind as to what effect beet pulp
might have on my adult horse's ability to absorb minerals, but since the
only data that I have available (from the magenesium statement in the first
study) is that it doesn't, to extrapolate the rat study to mature horses
requires me to "draw a conclusion based on facts not in evidence" (which in
both the legal and scientific worlds is considered a no-no).  The rat study
raises questions, but it doesn't answer any of them, at least not any
questions about horses...it may not even answer any questions about mature

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