As Louisville prepares for the 138th Kentucky Derby, horse racing in the US is under the spotlight over one its most controversial aspects.<br /><br />While there is big money for winners, every year thousands of under-performing thoroughbreds end up at the slaughterhouse. <br /><br />A total of 23 race horses either died or were injured on tracks across the US on the day of the competition last year.<br /><br />Now, a rescue centre is giving some lucky steeds a second chance.<br /><br />Al Jazeera's Kimberly Halkett reports from Kentucky.
