The World has a differing view on using a horse to set a pace (or kill off the speed), so another horse from the stable coming from off the pace has a better chance to win. Big stables in the UK, for example, want their well bred horses to win as many group one's as possible to increase the horse's worth in the breeding shed. This is one way to help.
This practice is technically against the rules in North America (and obviously not enforced), but it's not used often, and it's not particularly spelled out.
In places where it is accepted, it is spelled out, because, the betting public means something, of course. In the UK, pre-race, the horse being used as a rabbit is announced to bettors. This is why, as Sid Fernando put it today, Bullet Train, a very good horse in his own right, was 600-1 while being used as a rabbit for Frankel. I remember old Bullet Train 1000-1 at Betfair, where racegoers knew he was there as cannon fodder.
Places like Hong Kong, where you may think the Euro way would be followed, however, it's not. Rabbits are banned by the HKJC, and are not tolerated.
One quote from the Chief Steward for the HKJC caught my eye:
"Our rules don’t allow for pacemakers – we expect all runners in any race to employ tactics with the intention of winning or obtaining the best possible place in the field and that isn’t going to change," Kelly said. "And, if you are asking me for a personal opinion, the use of pacemakers in other jurisdictions is a blight on racing. Once you cross the line into allowing a horse to be ridden as a pacemaker for a better-fancied stablemate, you are allowing that horse to be run in a manner which may not be in its own best interests, and then I think you cross into very dangerous territory."That last line, "cross into very dangerous territory" reads prescient after watching the Sword Dancer, doesn't it? Being a rabbit for Flintshire wasn't quite enough, the horse had to be used as an offensive lineman at the head of the lane. A slippery slope indeed.
It's probably no surprise to frequent readers of the blog that I don't like gaming a race by using another horse to artificially inject pace. I love the pureness of the sport. I love 'my horse can beat your horse' spirit of it. I love the magic of a Zenyatta racing against glacial paces, and then seeing her overcome like the beast she was. I love seeing great horses proving they're great by winning races, not by winning races with help.
Horse racing is a beautiful sport when we let it unfold as it's intended.
Related - "Race Fixing for Me, But Not for Thee", via Crunk