Idaka told him that the feed he gave Oguri Cap had ingredients to help his body gain fat, and were not important for racing.

...wh-what...

It's all just instant noodles.

Even I don't eat so cheaply...

After Tsujimoto heard this, they stopped mixing that ingredient into Oguri Cap's feed.

Then in the Arima Kinen,

WOO— WOO—

After Tama's retirement, Idaka, with a bitter laugh, said, "I probably ended up helping the enemy back then."

Reference: Sanshindou, Legend of the Turf: Oguri Cap, Kano Yoichi.