Comparison of mandibular motion in horses chewing hay and pellets.
BACKGROUND
Previous studies have suggested that temporomandibular joint (TMJ) kinematics depend on the type of food being masticated, but accurate measurements of TMJ motion in horses chewing different feeds have not been published.


OBJECTIVE
The temporomandibular joint has a larger range of motion when horses chew hay compared to pellets.


METHODS
An optical motion capture system was used to track skin markers on the skull and mandible of 7 horses as they chewed hay and pellets. A virtual marker was created on the midline between the mandibles at the level of the 4th premolar teeth to represent the overall motion of the mandible relative to the skull during the chewing cycle.


RESULTS
Frequency of the chewing cycles was lower for hay than for pellets. Excursions of the virtual mandibular marker were significantly larger in all 3 directions when chewing hay compared to pellets. The mean velocity of the virtual mandibular marker during the chewing cycle was the same when chewing the 2 feeds.


CONCLUSIONS
The range of mediolateral displacement of the mandible was sufficient to give full occlusal contact of the upper and lower dental arcades when chewing hay but not when chewing pellets.


CONCLUSIONS
These findings support the suggestion that horses receiving a diet high in concentrate feeds may require more frequent dental prophylactic examinations and treatments to avoid the development of dental irregularities associated with smaller mandibular excursions during chewing.
Bonin
S J
SJ
McPhail Equine Performance Center, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan 48854, USA.
Clayton
H M
HM
Lanovaz
J L
JL
Johnston
T
T
D000821:Animal Feed; D000818:Animals; D001696:Biomechanical Phenomena; D006736:Horses / Q000502:physiology*; D008409:Mastication / Q000502:physiology*; D013704:Temporomandibular Joint / Q000502:physiology*