You must have a Fallabella on your account. This is a divine you can buy in the sales forum.

Without it you can not complete this objective.

If you have one of the Falabella divines (Tiny, Klein etc.) then they have a chance to trigger a bonus in your other horses when those other horses enter a competition. Each Falabella stacks a 1% chance for the bonus to trigger so if you only have one or two of the Falabellas it can be really hard to get the bonus to trigger - I only have one so when I get this objective, I just spam every horse I have into as many competitions as I can trying to get it. You'll know it's triggered as it will say on the daily actions of the horse who triggered it, either after or before the entry into the competition message.

Ok, great thank you for that info!
Sadly I have no Falabella, but still that was great help :3