No subject

Wed Feb 2 07:52:04 EST 2005

length of the palatine bone are reflected in a difference of lower teeth 
wear. 

Fred Horak
St. Jude's Farm
Lucas, TX

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<HTML>In a message dated 3/10/2003 12:04:49 PM Central Stand=
ard Time, oberlef at supernet.com writes: 
 
<BLOCKQUOTE TYPE=3DCITE style=3D"BORDER-LEFT: #0000ff 2px solid; MARGIN-LEFT=
: 5px; MARGIN-RIGHT: 0px; PADDING-LEFT: 5px">Listers- 
 Can anyone out ther=
e help me remember which way lamb mandibles grow?&nbsp; That is, is it the l=
ower mandible that grows faster than the upper one? A mismatched bite (with=20=
the teeth...lower jaw... coming up and past the upper pad).&nbsp;&nbsp; I th=
ink I remember hearing it was better to see a lamb whose bite did not meet h=
aving the lower jaw be too short rather than too long. Too bad this is a rea=
lly pretty lamb. 
 Katrina Lefever</FO=
NT> 
</BLOCKQUOTE> 
 
 
Peter Spellmeyer ... where are you? 
 
Two conditions of jaw misalignment are (1) brachygnathia, short lower jaw, s=
ometimes called "parrot mouth", and (2) brachygnathia superior, the maxilla,=
 the top bone, appears too short, the mandible (jaw) is too long, sometimes=20=
called "bulldog" or "monkey jaw". The maxilla has some special "parts" ...th=
e palatine bone is the section that supports the "gum pad", there is also a=20=
bone for the nasal cavity and a section called the lacrimal bone which runs=20=
from the eye to the nose.&nbsp;&nbsp; 
 
There are a number of possibilities for brachygnathia superior or "bulldog"=20=
mouth:: a normal maxilla (top part) and long mandible (jaw), too short a max=
illa and a normal mandible.&nbsp; The maxilla has several "parts" ... one or=
 more of those parts may be too short. 
 
Degree of misalignment or distance may be significant.&nbsp; A study by Erca=
nbrack and Knight on 12,000 jaws over 10 years used the folowing grades ...=20=
slight undershot or overshot as 0.1 cm or less in front or behind the dental=
 pad ...&nbsp; plain undershot or overshot as between 0.1cm and 0.5 cm. ...=20=
bad was greater than 0.5cm.&nbsp; I'm not sure how many Jacobs would pass a=20=
test of exact alignment ... perhaps alignment defined in terms of pastoral s=
urvival is more on point, i.e., can they live on pasture and thrive. 
 
Since sheep back teeth (molars) are hypsodont, they keep growing through lif=
e and some "parrot mouth" or lower jaw "realignment" may occur ...&nbsp; A s=
light "parrot mouth" condition may be corrected by age ... if it is slight.&=
nbsp;&nbsp; Your assumption about allowing the young "parrot mouth" to matur=
e is correct.&nbsp; However, this does not seem to occur with "bulldog mouth=
" which takes me back to the top bone, the maxilla and the various areas of=20=
the maxilla. 
 
If the "bulldog mouth" case is "obvious", you might get a sense of the sourc=
e of the difference by comparing the length of the maxilla (top from eyes to=
 nose) with other sheep in the flock.&nbsp; If a lamb's top of the nose is t=
oo short compared to the others ... a difference is observed ... one can che=
ck a little further by looking at the palatine bone (top gum plate) to see i=
f there is a shortness ... or is it truly a mandible that is too long.&nbsp;=
 
 
Another area to look at is the lacrimal area (tear duct area of the eye to n=
ose), is it shorter than others?&nbsp; Does either sire or dam or their pare=
nts have an evidently "bulbous" sinus? ...&nbsp; The nasal sinus bone sits "=
on top" of the maxilla and may be short with short lacrimal bones and thus a=
 shorter maxilla.&nbsp; 
 
The problem of jaw misalignment seems to be a recessive.&nbsp; There was a s=
tudy done on some commercial breeds that concluded that jaw deformities were=
 associated with level of inbreeding.