Possible Clues:

• Horse docked before bovine about 22 September?
• Event heralding spring
• Biannual event short of horses? Bull!
• One animal clipped before another on farm - it occurs twice a year
• Occasion when day and night are the same length
• Time of year horse lacks energy to mate with another animal
• Feature of spring, something shiny (not lead) and neat
• When night and day are of the same length
• March 21 occurrence