Here's what Red Horse Products has to say:
"Field Paste - antimicrobial sole and frog dressing
Field Paste is our anti-odour paste for horses which are mainly field kept. It has a thick paste-like consistency which offers greater 'staying power' as it remains in contact with the affected areas longer than other applications. This is designed to remain in the collateral grooves, central sulcus and on the sole for longer periods of time and continue having an effect against bacteria and fungi. At the same time it helps prevent mud, faeces and other contaminants coming in contact with the hoof.
We made this originally for brood stock that very rarely had their feet picked out. It is harder to spread than Sole Paint but has a longer residual effect.
Too thick to be painted on, Field Paste should be applied with a gloved hand. For stabled horses it is often better to use Sole Paint otherwise bedding gets stuck to the hoof and it is easier to apply, although a thin layer can still be used when stabled to prevent too much build up! "