There are a couple good reasons to pay attention to the shifting odds in the minutes leading up to a race.
The biggest one is that you want to know whether a horse you like is being overlooked by the other bettors, which means you will collect more if you are right and they are wrong. Such a horse is called an “overlay” and many players will increase their wagers in such a circumstance.
On the flip side, if you like a horse at 3-1 and she is bet down to 6-5, you probably should either pass the race or consider betting another horse that offers more attractive odds.
The other big reason to keep an eye on the odds is to look for horses that are being well bet even though they don’t show much in their recent races. That could signal that the horse’s “connections” – owner, trainer, groom, jockey, etc. – may think they’ve figured out why the horse hasn’t been performing well and are expecting a much improved effort today.
Finally, some players pay special attention to the “late money” that pours into the Tote system in the final minute or two of betting. They believe this is largely coming from “whales” – big bettors who use computers to predict which horse in a race is the best wager – and that a horse whose odds are ticking down in the waning seconds are likely to be winners. In my experience, chasing the so-called “smart money” will steer you in the wrong direction as often as it does in the right.