Equine Science Update
Reports from the world of  equine research.
Modern hoof repair materials.
© Copyright Equine Science Update 2005
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At a joint meeting of farriers and veterinarians at Stoneleigh, England, Ian Hughes, farrier at Liverpool Vet School reported on his experience of modern hoof repair materials.

He described the two types that are available in the UK. Their different properties  make each material more suited to certain uses than others.

Methacrylates: (eg Equilox; Bond n Flex; Jameg Shoe Glue) This is a resin, which  hardens when mixed with an accelerant. Although stable, both before and after mixing, it is hazardous. Good ventilation is important. The operator should wear gloves. The material releases heat as it sets. He suggests applying the material in layers to prevent excessive heat production.

Wrapping a layer of cling film around it as it sets produces a more even temperature throughout the material, leading to more uniform curing. It takes about 15 minutes for the initial cure and 24 hours for the finished cure. Hughes suggests keeping the horse stabled for 24 hours after application.

Polyurethanes: eg Vettec Superfast; Adhere; Ibex Fast Set)
These are almost non-hazardous, although they do produce noxious fumes if a hot shoe is fitted afterwards. The major downside is the heat they produce which can cause problems when used on sensitive parts of the foot. The initial cure time is about 30 seconds, and curing is finished in about 5 - 10 minutes. (“Superfast” may set slightly quicker but tends to be very hard, making it difficult to nail into.)

Preparation of the foot is all important. “If there are problems with the product it is probably because the foot hasn't been cleaned properly. The glue will not stick if wet. Degreasing is probably not necessary. Acetone leaves a residue, isopropyl alcohol may be better” he said. “But it is probably best just to keep the foot clean and dry.“ If the hoof is damp, Hughes recommends keeping the horse in a stable for a couple of days to dry out before using polyurethanes.


Common uses of methacrylate products.

Filling hoof wall defects.
First, trim and balance the foot, and fit and nail on the shoe. Remove all damaged hoof, and clean the foot thoroughly. Hughes prefers to use a rotating burr (eg Dremel ) to clean up the damaged horn. “It is less likely to damage the sensitive tissue.”  If sensitive tissues are exposed, or if the hoof wall is very thin,  cover them with a layer of Play Doh to prevent heat damage as the methacrylate cures.

Play Doh should not be left in place underneath the acrylic He suggests putting a match stick into any that is to be covered by acrylic. When the acrylic has set, drill through it and remove the Play Doh. Finally stick a small piece of tape over the hole to stop dirt getting in. “If there is  an adverse reaction within 24 hours it is either due to heat damage, or to leaving the Play Doh in place.”

To degrease the hoof ( “acetone works best”)  he advises giving the foot a good scrub just before applying the acrylic.

Glue on shoe.
To prepare the shoe, use a grinder to remove the fine grooves on the foot surface of the shoe, which would accumulate grease and prevent the glue sticking. Drilling four holes, at the toe and quarter each side, may hold the shoe more securely.

When applying the shoe he uses four spacers (“a chopped up mouse mat is fine”) so there is a gap between the foot and the shoe that will fill with acrylic. Apply the glue to the foot and the shoe, fit the shoe to the foot and wrap “cling film” around. it.

Remember the 15 minutes cure time. “You can drive nails in - even one or two make a difference” he said.  “They may help hold the shoe on”.

“Explain to the client that a lot of work was involved and the shoe still may fall off. The horse's environment and work will affect the ability of the shoe to stay put.”

Quarter crack repair.
The first step is to trim and balance the hoof.  Quarter cracks “invariably start with an imbalanced foot”.

Hughes advises trimming the hoof wall behind the crack, to prevent it bearing weight. He fits a heart bar or central support shoe, then debrides the crack, using a motorised burr. After degreasing the hoof  fit a plate across the crack. He advises holding the foot off the floor to keep the crack open as the glue cures. This leaves space for the horn tubules to grow and fill the crack..


Common uses of polyurethane products.

Derotation of the pedal bone.
Many horses have a rotated pedal bone as a result of a previous attack of laminitis. Hughes explained how polyurethane could be used to help restore the pedal bone to a more normal alignment.

Prepare the foot, trim the heels, and attach the shoe (usually a heart bar shoe) with heel nails. This leaves a gap between the shoe and the foot at the toe. Place a wedge between the shoe and foot at the toe, then fill the remaining gap with polyurethane. “You can put the foot down and let the horse stand, because the wedge will support the foot”.   Once the material has set, the wedge can be removed. This leaves a gap that can either be filled with more material  or left open if the area is painful.

Foal shoes
Foal shoes are used particularly to provide heel extensions. It helps to bandage the shoe in place while the glue sets.  Then check for any gaps in the polyurethane and top up if necessary. If using the Dalric foal shoes, he recommends removing the “fur” with a heat gun (otherwise there may be too much movement and the shoe may work loose.) Check and replace shoes every 2-3 weeks.

Foal extensions
To correct limb deviations it may be necessary to fix extensions to the foot. This can be done simply using polyurethane. Again, Hughes emphasises the importance of correct foot preparation. After trimming and cleaning, he recommends drying the hoof with a hot air gun. Then, he sticks a piece of “duck tape” under the foot, protruding at the front, to act as a scaffold on which he builds up the extension. When the material has set the tape can be removed and more material added  if necessary.

Tips for success.
According to Hughes:
·
“Generally the simpler the technique the better the outcome”.
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“It is important that the veterinarian and farrier work together.”
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“The working environment should be as near perfect as possible: a hospital environment is ideal - clean and dry, with good lighting.”
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“Sedation should be used every time as far as I am concerned”
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“Ensure you have enough time to do the procedure”
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Preparation is paramount. “I can't emphasise enough that with polyurethanes the foot must be as dry as possible.”



source: BEVA / NAFBAE meeting , Stoneleigh, UK. 29.11.05