....and let me reinforce all that Pam has said about using "ageing by the
teeth" in domestic horses with caution. The "old" incisor teeth Pam
mentions are actually incisor teeth indicating the animal's correct age,
+/- one year, which is as close as anyone can peg it after the age of 6.
A horse whose incisor-tooth "age" matches its chronological age is a
horse that has lived on range all or most of its life.
"Young" incisor teeth on horses known to be chronologically old are due to
malocclusion of the cheek teeth which stems from a diet of processed feeds
which does not cause the biologically-expected wear to the incisor teeth.
This is also why chronologically older domestic horses often have very
protuberant incisors or get 'long in the tooth': the accumulated excess
length, due to non-wear, forces the incisors to come into heavy occlusion
(because the incisors are so long that the cheek teeth cannot occlude),
and thus induces orthodontic change in the angle of the whole incisive
toothrow relative to the long axis of the skull.
"Wear" on anterior cheek teeth, which I have sometimes seen attributed to
"bit wear", is often not bit wear at all, but simply the natural
appearance of a deciduous premolar as it comes into senescence: the tooth
acquires a strong 'waist' in both lateral and occlusal view.
No horse ever takes a bit BETWEEN its anterior premolars and crunches down
on it, not even when the bit is made of leather or wood, and not even when
ridden with continuously tight reins. The horse will do anything to AVOID
TOUCHING the bit. "To take the bit between the teeth" is an expression for
a horse that pulls -- or bolts -- it seems to the human that this is what
occurs, but it's just a metaphor really. When a horse bolts, pulls, or
lugs, if the animal keeps its mouth closed, the bit is "held" either
against the anterior surface of the first large inferior cheek tooth (i.e.
P/2). Otherwise, the animal may take the strategy of opening its mouth, in
which case it permits the bit to be pulled back against the commissures of
the lips and/or the tongue, without closing its teeth against the bit.
This is why racehorses require tongue-ties, and why race trainers use
them: because horses commonly do open their mouths in face of the kind of
continuous back-pressure on the reins that is characteristic of the jockey
or polo player who "water-skis", i.e. rides with his feet ahead of his
butt, supporting his bodyweight by means of the reins. To defend itself,
the horse withdraws its tongue and uses the tongue (which is the largest
and strongest muscle in the upper one-third of the neck and head) to press
forward against the bit. However, the effort of supporting the rider's
bodyweight by the strength of its tongue, and the position of the tongue
necessary to effect this -- farther toward the back of the mouth than the
horse would carry its tongue if relaxed -- causes the caudal portion of
the tongue to jam up against the palatal drape, and both structures then
partially occlude the pharynx, which is part of the airway. Using a dry
hand or a dry glove, just before the start of the race trainer grasps the
horse's tongue, pulls it forward out of one side of the mouth, and then
ties it down with a leather or rubber strap so that the animal cannot
withdraw it for the duration of the race. This ensures an open airway --
and a faster horse -- for no horse can win if it can only intake half the
necessary air.
At the dental academy where I used to work, the technique of installing
'bit seats' was taught. This is a brilliant idea, which involves rasping
down the anterior 1/3rd of the superior and inferior P2's, so as to cause
the teeth, when occluded, to present upon their conjoint anterior aspect
the profile of a notch, like this if anterior were to the left: >. This
technique is medically dangerous if the notch is made too deep, i.e. if
the dentist unroofs the anterior pulp cavity of either tooth; but
otherwise it is not controversial. With 'bit seats' installed, when the
jockey pulls the bit back, the animal will keep its mouth closed because
the sloping 'ramp' of the inferior tooth enables the bit, when pulled
back, to ride up above the plane of the tongue, relieving the tongue of
the pressure which caused the animal to want to defend itself from the bit
in the first place. There is an ancillary piece of tack, a strap which
fits over the horse's nose, called a 'bit lifter' that can do the same
thing; and American cowboys know that when young horses show discomfort
when first being bitted, to lace a piece of twine around and through the
snaffle mouthpiece and then tie the ends up to the horse's foretop. They
then gradually let the bit down, day by day, as the horse comes to
understand and accept the bit. Of course, a better solution would be for
race trainers ALSO to learn how to show a horse how to emotionally come to
acceptance and equanimity with bits and with people who pull on the reins;
but as that approach appears to be absolutely hopeless, 'bit seats' are
the mechanical alternative.
In the political fight -- a territory fight currently going on between
licensed veterinarians and lay horse dentists, in which the veterinarians
have the greater depth of education, and mostly own the legal 'territory',
while the laymen often own the better techniques and have greater skill
and finesse -- there has been a good deal of ugliness, ungentlemanliness,
unfairness, and outright deception. The deceptions have been directed by
the veterinarians at the general public, by which they have claimed -- and
they ought to know better -- that (1) reducing excess accumulated length
of incisors is a form of 'bishoping' (it is in fact exactly the opposite,
but the public is easily fooled because they know no anatomy); and (2)
that installation of bit seats and/or reduction of excess accumulated
incisor length always exposes the pulp cavity, resulting in the mortality
of the tooth (which it certainly does not, but the procedure can be made
to look very scary to the ordinary horse owner). I mention this because if
anyone is studying recent publications on aging horses by the teeth, they
are sure to run into this kind of politically-motivated pseudo-education
and disinformation.
In a zooarchaeological context, I have waited with baited breath, and I
assure you I have also searched and kept my eye out, for any evidence of
tooth-rasping, floating, or equipment that could have been used or adapted
for this purpose. Did the Romans know? Did the Sarmatians know? The
Magyars?
Providence is inscrutable but nonetheless often kind. The oldest example
of a horse with cheek teeth that had obviously been floated I found while
sitting in the local auto repair shop a year ago while waiting for the
technician to "smog" my pickup truck. Naturally they had a stack of old
magazines in the waiting room, and idly flipping through an issue of
"National Geographic" I found an article on horses buried in full regalia
in some Chinese tomb -- four thousand years old or thereabouts if I
remember correctly. Seeing a photo closeup of one of the skulls I about
dropped my eyeteeth when I noticed the animal sported a beautiful
float-job.
As with stirrups, so with dental floats, the Chinese look to have been the
first. Cheers -- Dr. Deb
> Hi Adam
>
>
> I've done a fair amount of research in ageing horses. As Umberto has
> mentioned, the primary reference for cheek tooth wear is Marsha Levine's
> work. Please be aware of a few things...
>
>
> The are a variety of 'methods' for tooth-wear ageing in the clinical/vet
> literature, primarily for the anterior teeth. There are reasons for that.
> Ageing via cheek-tooth wear is highly unreliable and highly individual -
> dependent on individual morphology, genetics, habits and diet. I have
> examined modern horses with known ages where an 11 year old mare's teeth
> appeared 'older' than a 29 year old.
>
>
> Ageing on the other teeth is only considered strongly reliable under the
> age of 10. After that the same issues apply. Meaning it is better to
> simply indicate the horse is over 10 years and toothwear suggests it is
> possibly more than 15...20...
>
>
> If all you have are premolars/molars than Levine's work is it - but make
> judgements cautiously.
>
>
>
>
>
> Best regards
> Pam
>
> Pamela J Cross
> PhD researcher, Bioarchaeology
> Horses of Men & Gods project (AHRC, NT & MoL)
> Archaeological Sciences, University of Bradford, BD7 1DP UK
> p.j.cross (at) student.bradford.ac.uk / pajx (at) aol.com
> http://www.barc.brad.ac.uk/resstud_Cross.php
> http://bradford.academia.edu/PamCross
>
>
>
> -----Original Message-----
> From: adam heinrich <[log in to unmask]>
> To: ZOOARCH <[log in to unmask]>
> Sent: Sat, Feb 8, 2014 4:30 pm
> Subject: [ZOOARCH] horse age by tooth wear
>
>
>
> Dear ZOOARCH,
>
> Are there any accessible guides for aging horses by tooth wear,
> specifically premolar/molar wear? Most resources are limited to incisor
> wear.
>
> Thanks, Adam
>
>
>
>
>
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