Hope this helps.
Jim & Karen Clanin
_______________________________________________________
OK, here's another two cents regarding the use of DMG in endurance horses,
and specifically in answer to Dr. Lynn Taylor's statements that research has
not demonstrated its benefits. If anyone's comparing initials, my BS and
pending MS are both in Animal Science with an emphasis in equine exercise
physiology. DMG also happens to be very near and dear to my heart, the
subject of a study we did here at Cal Poly last year and the subject of lots
of heated debates around here. (I'm also engaged to a guy whose initals are
DMG, so you can imagine the comments I got to hear that I really do need to
try drinking decaf and maybe even get a life.)
Anyway, on to the debate---I think I may have an explanation for the
differnce between research and anecdotal evidence regarding DMG. Dr. Taylor
is absolutely correct that there is no research that clearly demonstrates
any benefits to performance horses performing maximal or submaximal
exercise. There was one study conducted on Standardbreds that supposedly
showed some "improvement in recovery" but the methodology in its statistical
design was so poor that any alleged results really must be totally
disregarded. Several other studies by Rose, Snow, as well as a study a year
or so ago conducted at Texas A & M, were all done with excellent attention
to detail and none of them showed any decrease in lactates while exercising.
HOWEVER---if the research literature is read carefully, there are several
important points to consider before you totally write off DMG. In all of
the previous studies, except for Cal Poly's, lactate levels were only
measured actually during the exercise bout itself, but not during the
subsequent recovery period. This is probably because the funding was coming
from the Thoroughbred racing industry, which very much wanted to know if DMG
would help a horse go faster during the race itself, but weren't
particularly interested with how stiff the horse felt the next day. The Cal
Poly project measured lactates not only during the exercise bout but ALSO
during the recovery period following the exercise test. This is because we
hypothesized that if DMG did provide any benefit, possibly it was during the
recovery period, rather than during the exercise period. That is, maybe the
horse still accumulated as many lactates, but DMG helped to clear it out
faster, which is almost as good. obviously, this would not benefit horses
such as Thoroughbreds which compete in a single, maximum effort event, but
would definitely benefit endurance horses which exercise for a time, rest
for a time and then exercise again. The second difference in Cal Poly's
study is that DMG was fed to the horses via syringe two to three hours
before data was collected. ALL of the prevous studies fed DMG to the
horses from eight to 24 hours before exercise. This is possibly a major
factor because DMG is a relatively small molecule---basically just a glycine
(an amino acid) molecule with two methyl groups tacked on. It's NOT going
to take very long for the equine system to get DMG into the system, broken
down, metabolized and waved goodbye to. It's a reasonable possibility that
in previous studies, by the time they got around to pulling blood and
measuring lactates, any benefits from the DMG fed yesterday had already been
and gone. It's the same thing as saying that aspirin doesn't work because
you took some last week and this week you have a headache again.
SO, when we did our study at Cal Poly, we fed the DMG at a time so that it
would be in the blood system while lactates were accumulating during the
treadmill exercise bout. We did a random, Latin square design so that every
horse did the test at three different levels of DMG dosage---zero, 2 mg/kg
and 4 mg/kg. At all three dosage levels, lactate accumulation was exactly
the same and oxygen utilization was the same. This confirms all the earlier
data that DMG is of NO benefit during an exercise test that was sufficient
to produce significant blood lactate levels. Also,in the zero and low
dosage group, there were no differences in lactate levels during the 90
minute recovery period. OK, here's the part where you pound your head and
think about going to work at Burger King like everyone else. We had
problems with lameness in a number of our test horses and by the time we
were done, the "high dosage" group had to be removed from the study because
they were no longer a statistically viable group. However, in the two high
dosage horses that did get measured, we did see a distinct and significant
drop in lactate levels during the thirty minutes immediately after the exercise
bout. When these two horses had previously done the same exercise test
twice before, once having been fed no DMG and once having been fed a low
dose of DMG, they did NOT show this drop in recovery lactates. This is a
SUGGESTION, AND A SUGGESTION ONLY, that MAYBE feeding DMG at 4 mg/kg or
higher provides some benefit during recovery. However, there is no way that
you can make any sort of broad statements after observing results in only
two horses. That would be the same thing as going into your backyard,
seeing two gray Arabs and therefore concluding that all horses are gray.
Therefore, the article that resulted from Cal Poly's study could only
mention the two statistically viable groups that showed no benefits from DMG.
So, to make a long story shorter, I think the only truly accurate statement
that could be made about DMG is that no research has YET proven any
benefits, however, the same research has also failed to completely DISPROVE
any benefits. To do so, someone is going to need to do another study in
which DMG is fed at high doses, fed within a few hours of the exercise bout,
and in which lactates are measured throughout the recovery period. And if
anyone cares to fund such a project, by all means let me know. Until then,
NO ONE can make any authoritative statements either for or against DMG's usage.
Susan Evans, MS (in progress)
Uppity Grad Student
Equine Research Center
Calif. State Polytechnic University, Pomona
suendavid@worldnet.att.net