You can only see this in the head on replay.
Castellano is riding the 2, Precious Lady. Prado is on 1, Ice Cool Kitty.
CAstellano's right rein breaks just out of the gate. Near the 1/2 pole (just before the camera angle changes), Prado, who is on the rail and immediately inside Castellano, reaches across in front of Precious Lady and, WITH HIS WHIP, moves the dangling right rein into Castellano's hand.
story:
http://www.dailygazette.com/news/2008/aug/03/803_mac/