When a horse is off the bit, or can't pick up the bridle, it means that they are giving 100% effort but still struggling to keep in contact with the leaders during the run.
This usually happens around the home turn, where the superior horses start to make their runs into the race, and the roughies all fall way despite being ridden hard.
As the bit/bridle restrains the horse, off the bit means the the jockey is giving his mount full reign, but it still can't keep up.
"That horse was off the bit before the final turn. He was no chance of winning that race."
