When you try to lead a horse it just opens the horse inventory.
MC-89924 Explains further bugs with horses but does not include this one.
Linked issues
Comments 3
Cannot confirm for 15w42a. Are you talking about skeleton or zombie horses, if so it is MC-75347
Resolving to MC-75347, would mark "cannot reproduce" otherwise - ticked closed, either way.
Please re-check this when MC-89924 gets fixed.