Occasionally leads do not work properly with horses and become removed from both the horse and the fence post it is attached to, this leaves the lead lying near the horse and fence post. from what i can tell this is not tied to the chunk being loaded as it does the same thing in the spawn chunk. This appears to affect the newly released 1.8.1 as well.
Related issues
duplicates
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migrated
Without more information, this is really a duplicate of MC-14826, not a relates to.