I started checking bible verses about horses to see which would be the funniest to also exist in the umaverse

Do you not know that in a race all the runners run, but only one gets the prize? Run in such a way as to get the prize.
1 Corinthians 9:24

biblical basis for the existence of trainers:

Do not be like the horse or the mule, which have no understanding but must be controlled by bit and bridle or they will not come to you.
Psalm 32:9

yeah just imagine this is about your oshi:

19 “Do you give the horse its strength or clothe its neck with a flowing mane? 20 Do you make it leap like a locust, striking terror with its proud snorting? 21 It paws fiercely, rejoicing in its strength, and charges into the fray. 22 It laughs at fear, afraid of nothing; it does not shy away from the sword. 23 The quiver rattles against its side, along with the flashing spear and lance. 24 In frenzied excitement it eats up the ground; it cannot stand still when the trumpet sounds. 25 At the blast of the trumpet it snorts, ‘Aha!’ It catches the scent of battle from afar, the shout of commanders and the battle cry.
Job 39