However, you could use these terms depending on the context:
* Field: This is the most common term used in racing.
* String: This term is usually used to refer to a group of horses owned by one person or stable.
* Stable: This refers to the entire group of horses, including those not currently racing, and their caretakers.
* Team: This can be used to refer to horses competing for a specific owner or trainer.
* Herd: This is a more general term for a group of horses, but it's not often used in the context of racing.
You can also be creative! If you're writing about a specific group of racehorses, you could give them a nickname based on their shared characteristics or the race they're competing in.