This is a vintage horse harness breast collar (also known as a breastplate).
 
 
Part Identification
The component shown includes:
Padded Breastplate: The thick, padded leather section that rests across the horse's chest, allowing it to push against the load.
Wither/Neck Strap: The red and yellow striped webbing that goes over the horse's neck to support the weight of the breast collar.
 
It has a strong horse scent.
 
Cultural and Design Significance (The internet search suggested this. There is also the possibility that the colours are just colours.)
 
The distinct red and yellow stripes are the colors of the Senyera, the official flag of Catalonia, Spain. This design is characteristic of traditional Spanish or Catalan harnesses, often used for stallions or during cultural exhibitions. While colored webbing is common in modern synthetic harnesses for endurance or pleasure driving, this specific pattern is a traditional regional identifier.