|Look at hair line|
|Solar view of same hoof|
You can see the Thrush infection in both the collateral grooves and central sulcus. Spreading the heels with this level of infection can be painful, so the horse lands toe first to avoid it. This sets up a spiralling series of problems, which can ultimately end with a diagnosis of navicular syndrome.
The trick is to sort the Thrush as a priority, which may also include dietary adjustments. There is no hard data, but experience suggests that horses which are in robust health and working hard (barefoot) tend to have much less of a problem in resisting this type of opportunistic infection.
The trimmers job is to sensitively put the heels back where they should be. This will take time and will not be successful if dietary and/or environmental issues are not addressed adequately.
This foot has also flared forward (see bottom half) but this is gradually growing out. Note the flare has to be grown out (and trimmed as you go along of course), you can't just chop lumps out of the foot to try and make it the correct shape immediately. Although if you look at some feet you can see where it has been tried.