As Louisville prepares for the 138th Kentucky Derby, horse racing in the US is under the spotlight over one its most controversial aspects.

While there is big money for winners, every year thousands of under-performing thoroughbreds end up at the slaughterhouse.

A total of 23 race horses either died or were injured on tracks across the US on the day of the competition last year.

Now, a rescue centre is giving some lucky steeds a second chance.

Al Jazeera's Kimberly Halkett reports from Kentucky.