These slides are from a talk Dr Jane Nixon equine vets has given on several occasions during 2012, including in November 2012 to the Yorkshire Show Horse and SHBGB on conformation, soundness and performance.
Transcript of “Bits and bitting”
1. BITS AND BITTING 2012 Jane Nixon MRCVS
2. Conformation of Dental Arcade Three-point balance refers to the correct function of:- THREE-POINT BALANCE 1. The incisors PLUS EXCURSION 2. The molars 3. The mandibular (jaw) joint Three-point balance allows normal jaw movements to take place and is achieved by:- • The removal of hooks • The removal of sharp points which develop on the outside of the upper and the inside of the lower premolars and molars • Adjusting the line of the incisors
3. Conformation of Dental Arcade• A purebred horse shows better conformation of the lower molar dental arcade fitting with the upper dental arcade than a crossbred horse.• Crossbred horses are more likely to have aberrant dental arcades with regard to the width, length and contours of the top and bottom jaws.• The angle of the head on the neck also makes a difference as to the fitting of the lower jaw to the upper jaw.• The factors alter the acceptance of the bit & the consequential muscle development & action of the horse
4. The jaw joint• (Temporo-mandibular), [unlike limb joints generally] are paired.• As with all synovial articulations they are subject to the traumatising effects of misuse.• Persisting pain in one side of the dental arcades will cause asymmetric functioning of both but more so on the affected side as the horse attempts to minimise this pain.• Osteoarthritis pain follows with even greater and further pain on masticatory movements.
5. • Lips (especially upper) Sense of touch and ability to feel and so involved in identification of foodstuff• Tongue Rostrally Sense of touch and feel of ingesta Sense of touch for presence of Caudally ingesta and sense of taste• Teeth (through alveoli and Sense of pressure on bite and so recognition of need to chew deeper to roots)• Sense of pressure especially of• Gums (bars) bit; important site of rein aid
6. • Hard Palate Sense of consistency of feed from pressure; and sense of pressure from feel up to pain as from the bit Sense of touch of food pressure• Inner cheeks Proprioceptor sensations• Jaw Joints
7. RememberA bridle, bit and reins in the ridden horse is for riding • Never tie up a horse by the reins • Never lead a horse for any great distance by the reins, certainly never with them still – Over the head and/or – In the martingale rings – A chiffney bit should only be used in skilled hands
8. • All living tissues will respond to careful and sensitive conditioning.• Epidermal tissues, skin and mucous membranes will sooner or later accept the usual sensory inputs and do so repeatedly without chronic inflammatory reactions such as fibrosing and hardening.• Repetition becomes habituation particularly in association with bit aids: the horse becomes used to the contacts without losing the automatic ability to remember the input message and to respond to it almost reflexly.
9. • ‘Mouthing’ a horse requires patience and ‘gentleness’ to the extent that the responses to the aids can become almost conditioned; the horse is almost a ‘step ahead’.• Memory of early training painful input can take longer to forget.• Any interference from pain in these areas and the associated evasion of the aids will variably influence the horse’s way of going even to disobedience and further misbehaviour.
10. Certain features of structure are important• The lines of the upper and lower arcades do not follow in parallel: The upper curves outwards and the lower describes a two converging straight lines• The distance between bars varies with o Breeds o Individuals within a breed o Left side to right side in an individual o Between upper & lower bars• These affect the effective ‘room for the bit’ and so subsequent applied bit pressure
11. • Tongue size, thickness and width relative to the space between the mandibular arms will affect the Cushioning effect of itself and that of the palate’s venous plexus Protective spread over the lower bars. These differences will also affect the ‘room for the bit’• The distance below the lower bars is always less than that between the enclosing fleshy (muscular) cheeks which must not be over compressed by the bit cheek pieces onto the rostral cheek teeth by fitting a too narrow a bit based on the bony intermandibular space ie the bars.
12. • In severe and/or repeated traumas a thrombosis of the blood supply to the thin layer of surface bone with subsequent ‘death’ of a sliver of that bone which now becomes a foreign body until such time as it is naturally sloughed off or manually removed.• Such an injury is known as a ‘broken jaw’.
13. Fore Quarters Hind Quarters No collar bone Bony Attachments
14. • HEAD CONFORMATION → JAW JOINT PAIN• → One sidedness• → Head Tilt• → Uneven back muscle development• → Poor saddle fit• → Hind leg lameness